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Preliminary validation of column-averaged volume mixing ratios of carbon dioxide and methane retrieved from GOSAT short-wavelength infrared spectra

Preliminary validation of column-averaged volume mixing ratios of carbon dioxide and methane... Atmos. Meas. Tech., 4, 1061–1076, 2011 Atmospheric www.atmos-meas-tech.net/4/1061/2011/ Measurement doi:10.5194/amt-4-1061-2011 © Author(s) 2011. CC Attribution 3.0 License. Techniques Preliminary validation of column-averaged volume mixing ratios of carbon dioxide and methane retrieved from GOSAT short-wavelength infrared spectra 1 1 1 1 1 2 3 2 2 I. Morino , O. Uchino , M. Inoue , Y. Yoshida , T. Yokota , P. O. Wennberg , G. C. Toon , D. Wunch , C. M. Roehl , 4 4 4 5 5 6 6 J. Notholt , T. Warneke , J. Messerschmidt , D. W. T. Griffith , N. M. Deutscher , V. Sherlock , B. Connor , 6 7 7 J. Robinson , R. Sussmann , and M. Rettinger National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan California Institute of Technology, Pasadena, CA, 91125-2100, USA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109-8099, USA Institute of Environmental Physics, University of Bremen, 28334 Bremen, Germany Center for Atmospheric Chemistry, University of Wollongong, New South Wales 2522, Australia National Institute of Water and Atmospheric Research, Wellington, New Zealand IMK-IFU, Karlsruhe Institute of Technology, Garmisch-Partenkirchen, Germany Received: 26 November 2010 – Published in Atmos. Meas. Tech. Discuss.: 8 December 2010 Revised: 25 April 2011 – Accepted: 19 May 2011 – Published: 15 June 2011 Abstract. Column-averaged volume mixing ratios of carbon 1 Introduction dioxide and methane retrieved from the Greenhouse gases The concentration of carbon dioxide (CO ) has increased Observing SATellite (GOSAT) Short-Wavelength InfraRed 2 from about 280 to 380 ppm over the past century due to observation (GOSAT SWIR X and X ) were compared CO CH 2 4 the burning of fossil fuels associated with expanding indus- with the reference calibrated data obtained by ground-based trial activities (IPCC, 2007). CO absorbs infrared radiation high-resolution Fourier Transform Spectrometers (g-b FTSs) 2 from the surface and hence an increase in CO concentrations participating in the Total Carbon Column Observing Net- leads to a rise in atmospheric temperature. CO and other work (TCCON). trace gases such as methane (CH ), nitrous oxide (N O), hy- 4 2 Preliminary results are as follows: the GOSAT SWIR drofluorocarbons (HFCs), perfluorocarbons (PFCs) and sul- X and X (Version 01.xx) are biased low by 8.85 CO CH 2 4 fur hexafluoride (SF ) are greenhouse gases that are subject ± 4.75 ppm (2.3 ± 1.2 %) and 20.4 ± 18.9 ppb (1.2 ± 1.1 %), to emissions regulations under the Kyoto Protocol. Together, respectively. The standard deviation of the GOSAT SWIR CO and CH account for over 80 percent of the total an- 2 4 X and X is about 1 % (1σ ) after correcting the neg- CO CH 2 4 thropogenic warming effect caused by all greenhouse gases ative biases of X and X by 8.85 ppm and 20.4 ppb, CO CH 2 4 based on the estimates of radiative forcing from 1750 to 2005 respectively. The latitudinal distributions of zonal means of (IPCC, 2007). Changes in temperature can cause feedbacks the GOSAT SWIR X and X show similar features to CO CH 2 4 that alter CO concentrations by influencing the biosphere those of the g-b FTS data except for the negative biases in (Cox et al., 2000). Methane in the atmosphere is determined the GOSAT data. by a balance between emission from the surface and loss in the soils and by OH radicals in the atmosphere. After almost a decade of near-zero growth, globally-averaged atmospheric methane increased during 2007 and 2008. The cause of this increase is not yet clear (Dlugokencky et al., 2009). To ac- curately predict future atmospheric CO and CH concentra- 2 4 tions and their impacts on climate, it is necessary to clarify Correspondence to: O. Uchino the distribution and variations of those sources and sinks. ([email protected]) Published by Copernicus Publications on behalf of the European Geosciences Union. 1062 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane Current estimates of CO flux from inverse methods rely processing such as monthly averaged X and X (Level 2 CO CH 2 4 mainly on ground-based data (Baker et al., 2006). Errors 3 products) and Level 4 carbon flux estimates. The primary in the estimation of regional fluxes from Africa and South purpose of the GOSAT is to make more accurate estimates of America are particularly large because ground-based moni- these fluxes on sub-continental scales (several hundred thou- toring stations are sparsely located in those regions. Spec- sand square kilometers) and contributing toward the broader troscopic remote sensing from space is capable of acquiring effort of environmental monitoring of ecosystem carbon bal- data that cover the globe and hence is expected to reduce ance. Further, through research using the GOSAT product, errors in the CO flux estimation using inverse modeling. new knowledge will be accumulated on the global distribu- To improve annual flux estimates on a sub-continental scale, tion of greenhouse gases and their temporal variations, as the required precision of monthly averaged column-averaged well as the global carbon cycle and its influence on climate. volume mixing ratio of carbon dioxide (X ) is less than These new findings will be utilized to improve predictions of CO ◦ ◦ 1 % on a 8 × 10 grid without biases or with uniform biases future climate change and its impacts. (Rayner and O’Brien, 2001; Houweling et al., 2004; Miller 2.2 GOSAT instruments and observation methods et al., 2007). To reduce the uncertainty in monthly, sub- continental (about 500 km) methane source strengths from Details of the GOSAT instruments have been described by satellite measurements, the precision of the column-averaged Kuze et al. (2009). GOSAT is placed in a sun-synchronous volume mixing ratios of methane is required to be 1–2 % orbit with an equator crossing time of about 13:00 local time, without systematic biases (Meirink et al., 2006). For this with an inclination angle of 98 degrees. GOSAT flies at an purpose, satellite-based data products must be validated by altitude of approximately 666 km and completes an orbit in higher-precision data obtained independently using ground- about 100 min. The spacecraft returns to observe the same based or aircraft measurements (Chahine et al., 2005; Suss- point on Earth every three days. The instruments onboard the mann et al., 2005; Dils et al., 2006; Schneising et al., 2008; satellite are TANSO-FTS and the TANSO Cloud and Aerosol Kulawik et al., 2010). Imager (TANSO-CAI). In this study, data products retrieved by the National Insti- TANSO-FTS has a Michelson interferometer that was cus- tute for Environmental Studies (NIES) from spectra obtained tom designed and built by ABB-Bomem, Quebec, Canada. by the Greenhouse gases Observing SATellite (GOSAT) are Spectra are obtained in four bands: band 1 spanning 0.758– compared with ground-based high-resolution Fourier Trans- −1 −1 0.775 μm (12 900–13 200 cm ) with 0.37 cm or better form Spectrometer (g-b FTS) data calibrated to the World spectral resolution, and bands 2–4, spanning 1.56–1.72, Meteorological Organization (WMO) scale. In Sect. 2, we 1.92–2.08, and 5.56–14.3 μm (5800–6400, 4800–5200, and present an overview of the GOSAT project, GOSAT in- −1 −1 700–1800 cm , respectively) with 0.26 cm or better spec- struments and observations, and retrievals from the GOSAT tral resolution. The TANSO-FTS instantaneous field of view Thermal And Near-infrared Sensor for carbon Observation is ∼15.8 mrad corresponding to a nadir footprint diameter Fourier Transform Spectrometer, measuring in the Short- of about 10.5 km at sea level. The nominal single-scan data Wavelength InfraRed (TANSO-FTS SWIR). Reference data acquisition time is 4 s. measured with g-b FTS are described in Sect. 3. Charac- TANSO-FTS observes solar light reflected from the earth’s teristics of GOSAT SWIR products and preliminary results surface as well as the thermal radiance emitted from the at- compared with the reference data are presented in Sect. 4, mosphere and the surface. The former (SWIR region) is ob- and the discussion and conclusions follow. served in bands 1 to 3 of the FTS in the daytime only, and the latter (Thermal InfraRed, TIR, region) is captured in band 4 during both the day and the night. The surface reflection 2 Overview of GOSAT, the GOSAT instruments, and characteristics of land and water differ significantly. The land data products retrieved from GOSAT TANSO-FTS is close to Lambertian, whereas the ocean is much more spec- SWIR observations ular. TANSO-FTS observes scattered sunlight over land us- ing a nadir-viewing observation mode, and over ocean using 2.1 GOSAT a sunglint observation mode. TANSO-CAI is a radiometer and observes the state of the GOSAT, launched on 23 January 2009, is the world’s first atmosphere and the surface during daytime. The image data satellite dedicated to measuring the atmospheric concentra- from CAI are used to determine cloud properties over an ex- tions of CO and CH from space. The GOSAT Project is 2 4 tended area that includes the FTS’ field of view as described a joint effort of the Ministry of the Environment (MOE), by Ishida and Nakajima (2009). As part of the retrieval, cloud the NIES, and the Japan Aerospace Exploration Agency characteristics and aerosol amounts are also retrieved. This (JAXA). NIES is responsible for (1) developing the retrieval information can be used to reject cloudy scenes and correct of greenhouse gas concentrations (Level 2 products) from the influence of aerosols on the retrieved X and X . CO CH 2 4 satellite and auxiliary data, (2) validating the retrieved green- house gas concentrations, and (3) producing higher-level Atmos. Meas. Tech., 4, 1061–1076, 2011 www.atmos-meas-tech.net/4/1061/2011/ I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1063 Over the three-day orbital repeat period, TANSO-FTS The column-averaged volume mixing ratio of CO (X ) 2 CO takes several tens of thousands of observations that cover or CH (X ) is defined to be the ratio of the CO (or CH ) 4 CH 2 4 the globe. Since the retrievals are limited to areas under column amount to the dry air column amount. To calculate clear sky conditions, only about ten percent of the spectra ob- the dry air column, the GFIT software uses the measured O tained by TANSO-FTS can be used for the retrieval of CO column, divided by the known dry air mole fraction of O 2 2 and CH . Nevertheless, the number of remaining data points (0.2095). The O column is measured simultaneously with 4 2 far surpasses the current number of ground monitoring sta- the CO and CH columns using the spectral band covering 2 4 tions used for analysis in the World Data Centre for Green- 1.25–1.29 μm. X and X are then obtained from: CO CH 2 4 house Gases (WDCGG), which is below 200 (WMO, 2009). X = 0.2095 (CO column/O column) CO 2 2 GOSAT serves to fill in the blanks in the ground observation network. X = 0.2095 (CH column/O column) CH 4 2 2.3 Products retrieved from GOSAT TANSO-FTS Ratioing by O minimizes systematic and correlated errors SWIR spectra present in both retrieved columns like pointing error, surface pressure uncertainty, instrument line shape uncertainty, H O The analysis of the TANSO-FTS SWIR spectra is described vapor uncertainty, zero level offsets and solar intensity vari- in detail by Yoshida et al. (2011). Briefly, absorption spec- ation (e.g. thin clouds). We use “uncertainty” as tra at bands 1 and 2 are used together to retrieve CO and 2 2 2 uncertainty = accuracy + precision CH column abundances. From all spectra observed with TANSO-FTS SWIR, only those measured without cloud in- accuracy = bias = systematic error terference are selected for further processing. Based on the absorption characteristics of each gas, the selected spectra precision = random error. are used to retrieve column abundances of CO and CH 2 4 (Level 2 product). The retrieval errors of X and X The precision of g-b FTS measurement of X is better than CO CH CO 2 4 2 are on average 2 ppm and 8 ppb or about 0.5 % respectively. 0.2 % under clear sky conditions (Washenfelder et al., 2006; The retrieval errors include TANSO-FTS SWIR measure- Ohyama et al., 2009; Wunch et al., 2011; Messerschmidt ment noise, smoothing error and interference error, and the et al., 2010). All TCCON X data are corrected for an CO main error is the measurement noise (Yoshida et al., 2011). airmass-dependent artifact (Wunch et al., 2011). Aircraft Variations in the CO concentration are most obvious near profiles obtained over many of these sites are used to deter- the surface of the earth. The CO absorption bands near mine an empirical scaling to place the TCCON data on the 1.6 μm and 2.0 μm provide information on the near-surface WMO standard reference scale. The scaling factors of X CO concentrations. On the other hand, the TIR absorption band and X are 1.011 and 1.022, respectively. The uncertainty CH around 14 μm is used to obtain information on the profiles of of X and X associated with the g-b FTS measurement CO CH 2 4 CO and CH , mainly at altitudes above 2 km (Saitoh et al., is estimated to be 0.8 ppm (∼0.2 %) and 4 ppb (∼0.2 %) by 2 4 2009). The retrievals from the TIR spectra and the validation comparing the TCCON retrievals with many different aircraft of their products will be presented in a forthcoming paper. profiles (Wunch et al., 2010). Validation of the TANSO-FTS SWIR Level 2 data prod- The g-b FTS data at nine TCCON sites are used in this uct is critical since the data are used for generating Level 3 analysis. Figure 1 shows the location of the FTS sites which and Level 4 products. GOSAT Level 2 products are evalu- are used in the present study. FTS sites are located in Asia, ated against high-precision data obtained independently us- Oceania, Europe, and North America. Table 1 summarizes ing ground-based or aircraft observations. Here we com- the spatial coordinates of those stations. pare the GOSAT SWIR X and X results with those CO CH 2 4 data obtained with ground-based high-resolution FTSs (g-b 4 Results of initial validation FTSs). 4.1 GOSAT product selection for validation 3 Reference data for GOSAT product validation The GOSAT SWIR X and X products used here are CO CH 2 4 Ver.01.xx. The retrieval algorithm for Ver.01.xx uses band 1 Spectra measured with g-b FTS are analyzed using the GFIT −1 −1 (12 900–13 200 cm ) and band 2 (5800–6400 cm ) to si- nonlinear least squares spectral fitting algorithm developed multaneously estimate X and X . In addition, the wa- CO CH at the Jet Propulsion Laboratory (Toon et al., 1992; Wunch 2 4 ter vapor column and aerosol optical depth (AOD) at a wave- et al., 2011), which is used for retrievals across all stations length of 1.6 μm are retrieved. Band 3 is used for selecting that comprise the Total Carbon Column Observing Network scenes with cirrus clouds which CAI can not detect (Yoshida (TCCON; Wunch et al., 2011). Here, we use the GFIT 7 Mar et al., 2011). Table 2 summarizes the spectral line parame- 2009 release. ters of CO , CH , H O and O molecules and the parameters 2 4 2 2 www.atmos-meas-tech.net/4/1061/2011/ Atmos. Meas. Tech., 4, 1061–1076, 2011 1064 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane Table 1. Ground-based FTS sites used for GOSAT product validation. Site Country Coordinate [Lat., Long.] Alt. [m a.s.l.] Reference ◦ ◦ Bialystok Poland 53.23 N, 23.0253 E 180 Messerschmidt et al. (2010) ◦ ◦ Orleans ´ France 47.965 N, 2.11253 E 130 Messerschmidt et al. (2010) ◦ ◦ Garmisch Germany 47.476 N, 11.0633 E 746.6 Sussmann et al. (2009) ◦ ◦ Park Falls USA 45.945 N, 90.2733 W 442 Washenfelder et al. (2006) ◦ ◦ Lamont USA 36.604 N, 97.4863 W 320 Wunch et al. (2010, 2011) ◦ ◦ Tsukuba Japan 36.0513 N, 140.12153 E 31 Ohyama et al. (2009) ◦ ◦ Darwin Australia 12.424453 S, 130.891543 E 32 Deutscher et al. (2010) ◦ ◦ Wollongong Australia 34.40633 S, 150.8793 E 30 ◦ ◦ Lauder New Zealand 45.03843 S, 169.6843 E 370 1 (a) 2 Fig.1. Fig. 1. Ground-based FTS sites used for the GOSAT product vali- dation in the present study. 4 (b) retrieved from bands 1 and 2 of TANSO-FTS. The grid point values of the meteorological data analyzed by the Japan Me- teorological Agency are interpolated to the retrieval points. The X and X data shown here (general public users, CO CH 2 4 or GU subset) are filtered for AOD less than 0.5. As a plane- parallel atmosphere is assumed in the retrieval, data with so- lar zenith angles greater than 70 degrees are not processed, and data over high mountain ranges such as the Rockies, the 18 Andes, and the Himalayan mountains are removed. 19 6 Fig.2. 20 7 Fig. 2. Global distribution of GOSAT SWIR X averaged 4.2 Global distribution of X and X CO CH CO 2 4 monthly in 1.5 by 1.5 degree bins for (a) April and (b) October 22 9 in 2009. 23 Figures 2 and 3 show the global distribution of the monthly- 10 24 11 averaged GOSAT SWIR X and X data, gridded in CO CH 2 4 25 ◦ ◦ 1.5 by 1.5 bins in April and October 2009, respectively. X is observed in both hemispheres. The standard devi- 26 CO 2 2 These retrievals satisfy the filter criteria over North Africa, ◦ ◦ ations of monthly mean X is about 1 % for a 10 × 10 CO the Arabian Peninsula, and Australia. Data over land are ob- grid over Australia, where gradients are anticipated to be ◦ ◦ tained mainly for 10–60 N and 15–45 S in April, and 10– very small. ◦ ◦ 50 N and 0–50 S in October. Data over ocean are retrieved X in the Northern Hemisphere is higher than in CH ◦ ◦ ◦ ◦ 4 in the regions of 10 S–30 N in April and 40 S–10 N in the Southern Hemisphere in both April and October 2009 October by observing the specular reflection of sunlight in (Fig. 3). Elevated X is observed from India to Japan in CH the direction of sunglint. October 2009. These features are similar to those obtained X in April is generally higher in the Northern Hemi- CO by SCIAMACHY (Frankenberg et al., 2006) and simulated sphere than the Southern Hemisphere (Fig. 2). This is be- by an inversion model (Bergamaschi et al., 2007). cause plant photosynthesis in the Northern Hemisphere is not yet competitive with respiration in April. In October, similar Atmos. Meas. Tech., 4, 1061–1076, 2011 www.atmos-meas-tech.net/4/1061/2011/ I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1065 Table 2. (a) Spectroscopic databases of CO , CH , H O and O molecules and (b) parameters retrieved from bands 1 and 2 of the TANSO 2 4 2 2 FTS in the Ver.01.xx. (a) Spectroscopic database Reference CO Voigt + Line mixing Lamouroux et al. (2010) CH Voigt HITRAN 2008 H O Voigt HITRAN 2008 O Voigt + Line mixing and collision-induced absorption Tran et al. (2006); Tran and Hartmann (2008) (b) Land surface albedo CO CH H O AOD surface press. temp. profile bias wavenumber dispersion 2 4 2 Ocean surface wind speed radiance adjust. factor 1 (a) GOSAT data are selected within about 0.5 to 1.5 degrees rect- angular area centered at each FTS site depending on the geo- graphical distribution of land and sea. As much as possible, we used only the GOSAT data retrieved over flat land. 4.3.1 X CO The time series of the GOSAT and g-b FTS data for X are CO shown on the left and their scatter diagrams on the right in Fig. 4. In the scatter diagram, we plotted data when g-b FTS data were collected within ±30 min of the GOSAT overpass time and corresponding GOSAT X values were success- CO fully retrieved. Therefore, the number of the GOSAT data in 4 (b) the scatter diagram is less than that in the time series. Only a few GOSAT data are available for comparison with Bia- lystok, Garmisch, Park Falls and Lauder. Darwin FTS data were not obtained from May 2010 through September 2010 due to mechanical problems with the sun tracker. X re- CO trieved from GOSAT SWIR measured near Orleans, ´ Lamont and Tsukuba sites are higher in boreal spring and lower in au- tumn (Fig. 4b, e, and f). A clear seasonality over the Northern Hemisphere can also be seen in the maps in Fig. 2. In con- trast, the seasonal variation of g-b FTS X in the Southern CO Hemisphere (i.e., Darwin, Wollongong, and Lauder) is weak 6 Fig.3. (Fig. 4g, h, and i) as expected due to smaller contribution of Fig. 3. Global distribution of GOSAT SWIR X averaged CH the continents. monthly in 1.5 by 1.5 degree bins for (a) April and (b) October Figure 5 shows the scatter diagram between the GOSAT in 2009. data and the g-b FTS data for all sites, and the slope of the regression line with no intercept is 0.977 with a corre- lation coefficient of 0.378 and Table 3 summarizes the dif- 4.3 Comparisons between g-b FTS data and GOSAT ference of the GOSAT data to the g-b FTS data at each site. TANSO-FTS SWIR data The difference of the GOSAT data to the g-b FTS data is GOSAT TANSO-FTS SWIR data are compared with the g-b −8.85 ± 4.75 ppm or −2.3 ± 1.2 %. FTS data at 9 TCCON sites (Fig. 1). We illustrate here the time series of the TANSO-FTS SWIR Level 2 data and g-b 4.3.2 X CH FTS data and their scatter diagrams for X and X . The CO CH 2 4 g-b FTS data are the mean values and standard deviations The time series of the GOSAT and g-b FTS data for X CH (1 σ ) measured at each FTS site within ±30 min of GOSAT are shown on the left and their scatter diagrams on the right overpass time (at most sites, around 13:00 local time). The in Fig. 6. The bias of X is smaller than that of X . CH CO 4 2 www.atmos-meas-tech.net/4/1061/2011/ Atmos. Meas. Tech., 4, 1061–1076, 2011 1066 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 400 400 (a) Table 3. Left side: the average and one standard deviation (1σ ) Bialystok Bialystok 390 390 of the difference between GOSAT X and g-b FTS X for CO CO 2 2 the nine TCCON sites. Right side: the average and one standard 380 380 deviation (1σ ) of the difference normalized to g-b FTS X (given CO 370 370 in percent). Note that the number of data listed here indicates the 360 360 count of valid cases in which g-b FTS data were collected within 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 Date g-b FTS X (ppm) CO2 ±30 min of the GOSAT overpass time and corresponding GOSAT 400 400 (b) Orleans Orleans X values were successfully retrieved. CO 390 390 380 380 Sites (GOSAT SWIR X ) – [(GOSAT SWIR X ) – CO CO 2 2 370 370 (g-b FTS X ) (g-b FTS X )]/ CO CO 2 2 (g-b FTS X ) CO 2 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 Number Average 1σ Average 1σ g-b FTS X (ppm) Date CO2 400 400 (c) of data (ppm) (ppm) (%) (%) Garmisch Garmisch 390 390 Bialystok 1 5.01 – 1.32 – Orleans ´ 14 −12.85 3.79 −3.33 0.99 380 380 Garmisch 3 −7.78 3.78 −2.00 0.96 370 370 Park Falls 1 −6.05 – −1.58 – Lamont 11 −10.31 4.80 −2.65 1.23 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 Tsukuba 13 −6.38 2.75 −1.64 0.71 g-b FTS X (ppm) Date CO2 400 400 Darwin 6 −6.09 2.61 −1.58 0.68 (d) Park Falls Park Falls Wollongong 11 −8.77 4.74 −2.28 1.23 390 390 Lauder 2 −7.45 0.15 −1.94 0.04 380 380 All data 62 −8.85 4.75 −2.29 1.23 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) Date CO2 5 Fig.4. Table 4. As in Table 3 except for X . CH Fig. 4. Time series of GOSAT TANSO-FTS SWIR (blue triangles) and g-b FTS (pink squares) X and their scatter diagrams for (a) CO Sites (GOSAT SWIR X ) – [(GOSAT SWIR X ) – 2 CH CH 4 4 Bialystok, (b) Orleans, ´ (c) Garmisch, (d) Park Falls, (e) Lamont, (f) (g-b FTS X ) (g-b FTS X )]/ CH CH 4 4 (g-b FTS X ) Tsukuba, (g) Darwin, (h) Wollongong, and (i) Lauder. CH Number Average 1σ Average 1σ of data (ppm) (ppm) (%) (%) 4.3.3 Remarks and relaxed coincidence criteria Bialystok 1 0.0227 – 1.29 – Orleans ´ 14 −0.0367 0.0178 −2.06 1.00 Garmisch 3 −0.0114 0.0160 −0.64 0.90 There are too few data points in Tables 3 and 4 to compute Park Falls 1 −0.0120 – −0.66 – meaningful statistics. For statistical significance, we have to Lamont 11 −0.0230 0.0181 −1.28 1.01 consider all the data (62) in Tables 3 and 4. For Orleans, ´ La- Tsukuba 13 −0.0120 0.0115 −0.67 0.64 Darwin 6 −0.0080 0.0089 −0.46 0.51 mont, Tsukuba and Wollongong, where there are more than Wollongong 11 −0.0235 0.0190 −1.34 1.08 10 coincident data points in Table 3, site-dependent biases Lauder 2 −0.0067 0.0003 −0.39 0.01 are the same within the mutual standard deviations. How- All data 62 −0.0204 0.0189 −1.15 1.06 ever, this is a topic for further investigation. We relaxed the coincidence criteria. Comparison of the GOSAT data retrieved within ±2 and ±5 degrees latitude/longitude box centered at each g-b FTS site and the In Lamont and Orleans, ´ X levels obtained from GOSAT CH mean values of the g-b FTS data measured within ±1 h of SWIR are higher in boreal autumn. The g-b FTS data of GOSAT overpass time can be found in Appendixes A and X over Tsukuba have a peak in summer rather than au- CH 4 B. For ±2 degree latitude/longitude, the GOSAT X and CO tumn. X are biased low by 8.57 ± 4.44 ppm (2.2 ± 1.2 %) and CH Figure 7 shows the scatter diagram between the GOSAT 15.8 ± 22.3 ppb (0.89 ± 1.26 %), respectively. For ±5 degree data and the g-b FTS data for all sites. The slope of the latitude/longitude, the GOSAT X and X are biased CO CH 2 4 regression line with no intercept is 0.998 and the correla- low by 8.25 ± 3.97 ppm (2.1 ± 1.0 %) and 14.8 ± 22.6 ppb tion coefficient is 0.681. The difference between the GOSAT (0.83 ± 1.27 %), respectively. These results are nearly equal data and the g-b FTS data at each site is shown in Table 4. to those in Tables 3 and 4. For these relaxed coincidence cri- The difference of the GOSAT data to the g-b FTS data is teria, site-dependent biases of the GOSAT X and X CO CH 2 4 −20.4 ± 18.9 ppb or −1.2 ± 1.1 %. are also the same within the mutual standard deviations Atmos. Meas. Tech., 4, 1061–1076, 2011 www.atmos-meas-tech.net/4/1061/2011/ X (ppm) X (ppm) XCO2 (ppm) X (ppm) CO2 CO2 CO2 GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) CO2 CO2 CO2 CO2 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1067 1 1 400 400 1.9 1.9 (e) (a) Lamont Lamont Bialystok Bialystok 390 390 1.8 1.8 380 380 1.7 1.7 370 370 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) Date g-b FTS X (ppm) Date CO2 CH4 2 2 400 400 1.9 1.9 (f) (b) Orleans Orleans Tsukuba Tsukuba 390 390 1.8 1.8 380 380 1.7 1.7 370 370 360 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 Date g-b FTS XCO2 (ppm) Date g-b FTS XCH4 (ppm) 3 3 400 400 1.9 1.9 (g) (c) Darwin Darwin Garmisch Garmisch 1.8 1.8 1.7 1.7 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) g-b FTS X (ppm) Date CO2 Date CH4 4 4 400 400 1.9 1.9 (h) (d) Wollongong Wollongong Park Falls Park Falls 390 390 1.8 1.8 380 380 1.7 1.7 370 370 360 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 Date g-b FTS XCO2 (ppm) Date g-b FTS XCH4 (ppm) 400 400 (i) 5 Fig.7. Lauder Lauder 390 390 Fig. 6. Time series of GOSAT TANSO-FTS SWIR (blue triangles) 380 380 and g-b FTS (pink squares) X and their scatter diagrams for (a) CH Bialystok, (b) Orleans, (c) Garmisch, (d) Park Falls, (e) Lamont, (f) 370 370 Tsukuba, (g) Darwin, (h) Wollongong, and (i) Lauder. 360 360 10 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS XCO (ppm) Date 2 6 Fig.5. because the standard deviations of the biases are large at re- Fig. 4. Continued. 5 specti ve FTS sites. However, the peak-to-peak variation of the biases from site to site is now 1.2–1.8 %. We have to Bialystok 400 investigate further to decrease the variation of the biases. Orleans Garmisch 4.4 Latitudinal distributions of zonal averaged GOSAT ParkFalls SWIR X and X CO CH 2 4 Lamont Tsukuba In Sect. 4.3, g-b FTS data recorded within ±30 min of the Darwin GOSAT overpass were used for the validation. To obtain larger numbers of samples and depict the latitudinal features, Wollongong we calculated monthly mean X and X of g-b FTS Lauder CO CH 2 4 data obtained within ±30 min of the time when GOSAT is supposed to overpass for all days, including the days when GOSAT does not overpass each site. In addition, monthly 360 370 380 390 400 mean values of zonal averaged GOSAT data, based on all FTS X (ppm) CO 2 data obtained, are calculated in each 15 degree latitudinal band. 3 Fig.6. Fig. 5. Scatter diagram between GOSAT TANSO-FTS SWIR and Latitudinal distributions of monthly means of zonal aver- g-b FTS X at all FTS sites. CO aged GOSAT SWIR and g-b FTS data of X in April and 2 CO October 2009 are shown in Fig. 8. Both data sets show that X is higher in the Northern Hemisphere compared with CO 7 the Southern Hemisphere in April and the difference between www.atmos-meas-tech.net/4/1061/2011/ Atmos. Meas. Tech., 4, 1061–1076, 2011 GOSAT SWIR X CO2 (ppm) X (ppm) X (ppm) X (ppm) X (ppm) X (ppm) CO2 CO2 CO2 CO2 CO2 GOSAT SWIR XCO2 (ppm) GOSAT SWIR XCO2 (ppm) GOSAT SWIR XCO2 (ppm) GOSAT SWIR XCO2 (ppm) GOSAT SWIR XCO2 (ppm) X (ppm) X (ppm) X (ppm) X (ppm) CH4 CH4 CH4 CH4 GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) CH4 CH4 CH4 CH4 1068 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1.9 1.9 (e) Lamont Lamont 1.9 Bialystok 1.8 1.8 Orleans Garmisch 1.7 1.7 ParkFalls 1.8 Lamont 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) Date CH4 Tsukuba 1.9 1.9 (f) Tsukuba Tsukuba Darwin Wollongong 1.8 1.8 1.7 Lauder 1.7 1.7 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 1.6 g-b FTS X (ppm) Date CH4 1.9 1.9 1.6 1.7 1.8 1.9 (g) Darwin Darwin FTS X (ppm) CH4 1.8 1.8 1.7 1.7 3 Fig.9. Fig. 7. Scatter diagram between GOSAT TANSO-FTS SWIR and g-b FTS X at all FTS sites. CH 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 Date g-b FTS X (ppm) CH4 1.9 1.9 (h) Wollongong Wollongong reduced compared with earlier versions of the retrievals 1.8 1.8 (Yokota et al., 2009). The earlier versions (Ver.00.yy) used 1.7 1.7 only band 2 of TANSO-FTS and retrieved CO and CH 2 4 columns separately and estimates X and X using a CO CH 2 4 1.6 1.6 10 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 dry-air column calculated from meteorological data analyzed Date g-b FTS XCH4 (ppm) by the Japan Meteorological Agency. Over the Sahara Desert 1.9 1.9 (i) Lauder Lauder and Arabian Peninsula and their surrounding areas, appar- 1.8 1.8 ent high values of X and X were retrieved due to CO CH 2 4 14 the influences of dust particles. In Ver.01.xx released in Au- 1.7 1.7 gust 2010, bands 1 and 2 of TANSO-FTS were used for si- 1.6 1.6 multaneous retrieval of CO and CH columns with surface 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 2 4 Date g-b FTS XCH4 (ppm) pressure. Therefore, the apparent high values of X and CO 6 Fig.8. X almost disappeared over the Sahara Desert and their CH Fig. 6. Continued. surrounding areas thanks to the correction of the extended optical paths by the elevated dust particles. However, bias due to aerosols and thin cirrus clouds the hemispheres is small in October. The difference of X CO still exists because of the anomalously low X retrievals CO between April and October is about 5 ppm in the northern (Fig. 2). In the future, we plan to investigate interferences mid latitudes for both data sets. The zonal means of GOSAT by aerosols and thin cirrus clouds using aerosol lidars and/or data are reasonably consistent with those of the reference val- sky-radiometers at selected FTS sites. ues, apart from the overall biases. The negative bias of about 9 ppm or 2.3 % in the GOSAT Figure 9 shows latitudinal distributions of monthly means TANSO-FTS SWIR data of X is not still understood. CO of zonal averaged GOSAT SWIR and g-b FTS data of X CH It may result from unknown spectroscopic parameters of for April and October 2009. X is characterized by rel- CH O and CO or error in the TANSO-FTS calibration. In 2 2 atively high concentrations in the Northern Hemisphere in the case of the GOSAT SWIR data of X , the negative CH April and October. Moreover, the bias is smaller than that bias decreased in the Ver.01.xx compared with the earlier of X . In particular, the concentration of X of GOSAT CO CH 2 4 Ver.00.yy when the spectroscopic parameters were changed data is in good agreement with that of g-b FTS sites in April. from Lyulin et al. (2009) to HITRAN 2008 database (Roth- Both X data in October show a similar distribution. CH man et al., 2009). Therefore it is important to further exam- ine the spectroscopic parameters of O , CO and CH . 2 2 4 Some instrumental issues occurred since the launch of 5 Discussion GOSAT, which could also contribute to the biases. The sam- In this study, we validated the GOSAT TANSO-FTS SWIR pling laser wavelength of TANSO-FTS shifted in time prob- X and X against the TCCON g-b FTS instruments. ably due to the change of the 1.31-μm distributed-feedback CO CH 2 4 In Ver.01.xx, the influence of aerosols has been markedly laser cavity length. The sensitivity of band 1 decreased after Atmos. Meas. Tech., 4, 1061–1076, 2011 www.atmos-meas-tech.net/4/1061/2011/ XCH4 (ppm) XCH4 (ppm) XCH4 (ppm) XCH4 (ppm) XCH4 (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR XCH4 (ppm) CH4 CH4 CH4 CH4 GOSAT SWIR X (ppm) CH4 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1069 3 Fig. 9. As Fig. 8 but for X . CH Fig. 8. Latitudinal distributions of monthly means of zonal aver- 6 Fig.11. and X . This could decrease the standard deviation of the CH aged GOSAT X for each 15 latitudinal band in April and Oc- CO GOSAT X and X . To what extent topographies sur- 6 Fig.10. CO CH 2 4 tober 2009 (blue triangles). The monthly means of g-b FTS data rounding g-b FTS sites influence the data quality, is not clear observed during local time of about 12:30–13:30 hour are shown at present. We will investigate this effect in the near future. by pink squares. Vertical bars indicate the standard deviation. 6 Conclusions the launch. These effects are corrected before retrieving The GOSAT TANSO-FTS SWIR data of X and X CO CH 2 4 X and X . A TANSO-FTS pointing error occurred CO CH in the Version 01.xx were compared against reference 2 4 when the pointing mirror was moved largely to the along- data obtained with the TCCON g-b FTS sites. The track direction. This error causes the mismatch of the field GOSAT TANSO-FTS SWIR X and X were biased CO CH 2 4 of views between CAI and TANSO-FTS, and misleads the low by 8.85 ± 4.75 ppm (2.3 ± 1.2 %) and 20.4 ± 18.9 ppb cloud screening algorithm. However, in the case of the spe- (1.2 ± 1.1 %) respectively versus the reference values. The cial point observation mode of TANSO-FTS to g-b FTS sites, standard deviation of the GOSAT SWIR X and X CO CH 2 4 the mismatch should be small. retrievals is considered to be about 1 % (1 σ ) after correcting the negative biases by 8.85 ppm and 20.4 ppb, respectively. The standard deviation of the GOSAT SWIR X and CO Although X is underestimated by approximately X is about 1 % (1 σ ) after correcting the negative biases CO CH 2 9 ppm, the GOSAT retrievals and g-b FTS data show simi- by 8.85 ppm and 20.4 ppb, respectively, and it is larger than lar seasonal behaviors over the Northern Hemisphere: higher those of the g-b FTS data (∼0.2 %). The retrieval errors of in spring and lower in autumn. The latitudinal distribution X and X are on average 2 ppm and 8 ppb or about CO CH 2 4 of zonal averaged GOSAT SWIR X and X is broadly 0.5 % respectively. This means that the other errors of about CO CH 2 4 consistent with that of the g-b FTS except for the larger nega- 0.5 % are due to influences of factors such as aerosols and tive biases in the GOSAT data. We plan further studies to ad- thin cirrus clouds. In the retrieval algorithm of Ver.01.xx, dress the negative bias of the GOSAT SWIR X and X aerosols are assumed to exist homogeneously below 2-km al- CO CH 2 4 as well as to better understand the influence of aerosols and titude. In the near future retrieval algorithm, the vertical pro- thin cirrus clouds. files of aerosols will be simultaneously retrieved with X CO www.atmos-meas-tech.net/4/1061/2011/ Atmos. Meas. Tech., 4, 1061–1076, 2011 1070 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane Table A1. Left side: the average and one standard deviation (1σ ) Table A2. As in Table A1 except for X . CH of the difference between GOSAT X and g-b FTS X for CO CO 2 2 the nine TCCON sites. Right side: the average and one standard deviation (1σ ) of the difference normalized to g-b FTS X (given Sites (GOSAT SWIR X ) – [(GOSAT SWIR X ) – CH CH CO 2 4 4 (g-b FTS X ) (g-b FTS X )]/ in percent). The GOSAT data were retrieved within ±2 degrees CH CH 4 4 (g-b FTS X ) CH latitude/longitude box centered at each g-b FTS site and the g-b Number Average 1σ Average 1σ FTS data were the mean values measured within ±1 h of GOSAT of data (ppm) (ppm) (%) (%) overpass time. Bialystok 3 −0.0107 0.0306 −0.61 1.73 Orleans ´ 18 −0.0383 0.0191 −2.14 1.07 Garmisch 3 −0.0111 0.0170 −0.62 0.95 Sites (GOSAT SWIR X ) – [(GOSAT SWIR X ) – CO CO 2 2 Park Falls 14 −0.0116 0.0213 −0.65 1.19 (g-b FTS X ) (g-b FTS X )]/ CO CO 2 2 Lamont 126 −0.0108 0.0213 −0.60 1.18 (g-b FTS X ) CO Tsukuba 23 −0.0101 0.0135 −0.57 0.75 Number Average 1σ Average 1σ Darwin 9 −0.0153 0.0141 −0.87 0.80 of data (ppm) (ppm) (%) (%) Wollongong 57 −0.0237 0.0243 −1.36 1.39 Lauder 3 −0.0170 0.0179 −0.98 1.03 Bialystok 3 −6.68 10.04 −1.72 2.61 Orleans ´ 18 −13.01 3.59 −3.37 0.93 All data 256 −0.0158 0.0223 −0.89 1.26 Garmisch 3 −7.71 3.24 −1.98 0.82 Park Falls 14 −7.72 4.11 −1.99 1.06 Lamont 126 −8.28 3.88 −2.13 1.00 Tsukuba 23 −6.09 2.77 −1.57 0.71 400 400 (a) Bialystok Bialystok Darwin 9 −7.83 3.39 −2.03 0.88 390 390 Wollongong 57 −9.24 5.38 −2.39 1.39 Lauder 3 −9.70 3.86 −2.52 0.99 380 All data 256 −8.57 4.44 −2.21 1.15 370 370 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS XCO2 (ppm) Date 400 400 (b) Orleans Orleans 390 390 Appendix A 380 380 Comparison of GOSAT and g-b FTS data within ±2 degrees and ±1 h 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) CO2 Date 400 400 We performed comparison of the GOSAT data retrieved (c) Garmisch Garmisch within ±2 degrees latitude/longitude box centered at each g- 390 390 b FTS site and the mean values of the g-b FTS data measured 380 380 within ±1 h of GOSAT overpass time. 370 370 The time series of the GOSAT and g-b FTS data for X CO are shown on the left and their scatter diagrams on the right 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) CO2 Date in Fig. A1. Figure A2 shows the scatter diagram between 400 400 (d) Park Falls Park Falls the GOSAT data and the g-b FTS data for all sites, and the 390 390 slope of the regression line with no intercept is 0.978 with 380 380 a correlation coefficient of 0.319 and Table A1 summarizes 370 370 the difference of the GOSAT data to the g-b FTS data at each 360 360 site. The difference of the GOSAT data to the g-b FTS data 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) Date CO2 is −8.57 ± 4.44 ppm or −2.2 ± 1.2 %. 5 Fig.A1. The time series of the GOSAT and g-b FTS data for X CH Fig. A1. Time series of GOSAT TANSO-FTS SWIR (blue trian- are shown on the left and their scatter diagrams on the right gles) and g-b FTS (pink squares) X and their scatter diagrams CO in Fig. A3. Figure A4 shows the scatter diagram between the for (a) Bialystok, (b) Orleans, ´ (c) Garmisch, (d) Park Falls, (e) La- GOSAT data and the g-b FTS data for all sites. The slope of mont, (f) Tsukuba, (g) Darwin, (h) Wollongong, and (i) Lauder. The the regression line with no intercept is 0.991 and the correla- GOSAT data were retrieved within ±2 degrees latitude/longitude tion coefficient is 0.794. The difference between the GOSAT box centered at each g-b FTS site and the g-b FTS data were the data and the g-b FTS data at each site is shown in Table A2. mean values measured within ±1 h of GOSAT overpass time. The difference of the GOSAT data to the g-b FTS data is −15.8 ± 22.3 ppb or −0.89 ± 1.3 %. Atmos. Meas. Tech., 4, 1061–1076, 2011 www.atmos-meas-tech.net/4/1061/2011/ X (ppm) X (ppm) X (ppm) X (ppm) CO2 CO2 CO2 CO2 GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1071 400 400 1.9 1.9 (e) (a) Lamont Lamont Bialystok Bialystok 390 390 1.8 1.8 380 380 1.7 1.7 370 370 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS XCO2 (ppm) g-b FTS X (ppm) Date CH4 Date 400 400 1.9 1.9 (f) (b) Tsukuba Tsukuba Orleans Orleans 390 390 1.8 1.8 1.7 1.7 370 370 360 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) g-b FTS X (ppm) Date CO2 Date CH4 3 3 400 400 1.9 1.9 (g) (c) Darwin Darwin Garmisch Garmisch 390 390 1.8 1.8 380 380 1.7 1.7 370 370 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) g-b FTS XCH4 (ppm) CO2 Date Date 1.9 1.9 400 400 (d) (h) Park Falls Park Falls Wollongong Wollongong 390 390 1.8 1.8 1.7 1.7 370 370 1.6 1.6 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS XCH4(ppm) g-b FTS X (ppm) Date Date CO2 400 400 5 Fig.A4. (i) Lauder Lauder 390 390 Fig. A3. Time series of GOSAT TANSO-FTS SWIR (blue trian- gles) and g-b FTS (pink squares) X and their scatter diagrams 380 380 CH for (a) Bialystok, (b) Orleans, ´ (c) Garmisch, (d) Park Falls, (e) La- 370 370 mont, (f) Tsukuba, (g) Darwin, (h) Wollongong, and (i) Lauder. The GOSAT data were retrieved within ±2 degrees latitude/longitude 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS XCO2 (ppm) Date box centered at each g-b FTS site and the g-b FTS data were the 6 Fig.A2. mean values measured within ±1 h of GOSAT overpass time. Fig. A1. Continued. 13 400 Bialyst ok Orleans Garmisch ParkFalls Lamont Appendix B Tsukuba Darw in Comparison of GOSAT and g-b FTS data within W ollongong ±5 degrees and ±1 h 370 Lauder We performed comparison of the GOSAT data retrieved 360 within ±5 degrees latitude/longitude box centered at each g- 360 370 380 390 400 b FTS site and the mean values of the g-b FTS data measured FT S X CO2 (ppm) within ±1 h of GOSAT overpass time. The time series of the GOSAT and g-b FTS data for X CO 3 Fig.A3. Fig. A2. Scatter diagram between GOSAT and g-b FTS X at CO are shown on the left and their scatter diagrams on the right all FTS sites. The GOSAT data were retrieved within ±2 degrees in Fig. B1. latitude/longitude box centered at each g-b FTS site and the g-b Figure B2 shows the scatter diagram between the GOSAT FTS data were the mean values measured within ±1 h of GOSAT data and the g-b FTS data for all sites, and the slope of overpass time. 8 the regression line with no intercept is 0.979 with a corre- lation coefficient of 0.285 and Table B1 summarizes the dif- ference of the GOSAT data to the g-b FTS data at each site. www.atmos-meas-tech.net/4/1061/2011/ Atmos. Meas. Tech., 4, 1061–1076, 2011 XCO2(ppm) XCO2(ppm) XCO2(ppm) XCO2(ppm) X (ppm) CO2 GOSAT SWIR X CO2 (ppm) GOSAT SWIR X (ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) CO2 X (ppm) X (ppm) X (ppm) X (ppm) CH4 CH4 CH4 CH4 GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) CH4 CH4 CH4 CH4 1072 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1.9 1.9 (e) Lamont Lamont Table B1. Left side: the average and one standard deviation (1σ ) of the difference between GOSAT X and g-b FTS X for CO CO 1.8 1.8 2 2 the nine TCCON sites. Right side: the average and one standard 1.7 1.7 deviation (1σ ) of the difference normalized to g-b FTS X (given CO in percent). The GOSAT data were retrieved within ±5 degrees 1.6 1.6 latitude/longitude box centered at each g-b FTS site and the g-b 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) Date CH4 2 FTS data were the mean values measured within ±1 h of GOSAT 1.9 1.9 (f) Tsukuba Tsukuba overpass time. 1.8 1.8 1.7 1.7 Sites (GOSAT SWIR X ) – [(GOSAT SWIR X ) – CO CO 2 2 (g-b FTS X ) (g-b FTS X )]/ CO CO 2 2 1.6 1.6 (g-b FTS X ) CO 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) Date CH4 3 Number Average 1σ Average 1σ 1.9 1.9 (g) Darwin Darwin of data (ppm) (ppm) (%) (%) 1.8 1.8 Bialystok 26 −6.76 4.38 −1.75 1.13 Orleans ´ 59 −10.24 3.75 −2.65 0.97 1.7 1.7 Garmisch 15 −6.58 2.35 −1.71 0.60 Park Falls 104 −8.24 4.07 −2.13 1.05 1.6 1.6 Lamont 513 −8.29 3.60 −2.14 0.92 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) CH4 Date Tsukuba 29 −5.61 3.33 −1.44 0.86 1.9 1.9 (h) Wollongong Wollongong Darwin 72 −7.41 3.04 −1.92 0.79 Wollongong 143 −8.72 5.22 −2.26 1.35 1.8 1.8 Lauder 5 −7.02 4.57 −1.83 1.18 1.7 1.7 All data 966 −8.25 3.97 −2.10 1.02 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 Date g-b FTS XCH4 (ppm) 1.9 1.9 (i) Lauder Lauder Table B2. As in Table B1 except for X . CH 1.8 1.8 Sites (GOSAT SWIR X ) – [(GOSAT SWIR X ) – 1.7 1.7 CH CH 4 4 (g-b FTS X ) (g-b FTS X )]/ CH CH 4 4 (g-b FTS X ) 1.6 1.6 CH 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS XCH4(ppm) Date Number Average 1σ Average 1σ 6 Fig.A5. of data (ppm) (ppm) (%) (%) Fig. A3. Continued. Bialystok 26 −0.0072 0.0238 −0.41 1.35 Orleans ´ 59 −0.0230 0.0183 −1.29 1.03 Garmisch 15 0.0032 0.0152 0.18 0.85 1.9 Bialyst ok Park Falls 104 −0.0166 0.0225 −0.92 1.25 Orleans Lamont 513 −0.0132 0.0230 −0.73 1.28 Garmisch Tsukuba 29 −0.0077 0.0165 −0.43 0.92 Darwin 72 −0.0140 0.0123 −0.80 0.70 ParkFalls 1.8 Wollongong 143 −0.0218 0.0253 −1.25 1.45 Lamont Lauder 5 −0.0030 0.0230 −0.17 1.33 Tsukuba Darw in All data 966 −0.0148 0.0226 −0.83 1.27 W ollongong 1.7 Lauder The difference of the GOSAT data to the g-b FTS data is 1.6 −8.25 ± 3.97 ppm or −2.1 ± 1.0 %. 1.6 1.7 1.8 1.9 FT S X CH4 (ppm) The time series of the GOSAT and g-b FTS data for X CH are shown on the left and their scatter diagrams on the right 3 Fig.A6. Fig. A4. Scatter diagram between GOSAT and g-b FTS X at CH in Fig. B3. Figure B4 shows the scatter diagram between the all FTS sites. The GOSAT data were retrieved within ±2 degrees GOSAT data and the g-b FTS data for all sites. The slope of latitude/longitude box centered at each g-b FTS site and the g-b the regression line with no intercept is 0.992 and the correla- FTS data were the mean values measured within ±1 h of GOSAT tion coefficient is 0.712. The difference between the GOSAT overpass time. data and the g-b FTS data at each site is shown in Table B2. The difference of the GOSAT data to the g-b FTS data is −14.8 ± 22.6 ppb or −0.83 ± 1.3 %. Atmos. Meas. Tech., 4, 1061–1076, 2011 www.atmos-meas-tech.net/4/1061/2011/ X (ppm) X (ppm) X (ppm) X (ppm) CH4 CH4 CH4 CH4 X (ppm) CH4 GOSAT SWIR X CH4 (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) CH4 CH4 CH4 CH4 CH4 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1073 400 400 400 400 (a) (e) Bialystok Bialystok Lamont Lamont 390 390 390 390 380 380 380 380 370 370 370 370 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) Date CO2 g-b FTS X (ppm) CO2 Date 400 400 (b) 400 400 (f) Orleans Orleans Tsukuba Tsukuba 390 390 390 390 380 380 370 370 360 360 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS XCO2 (ppm) Date g-b FTS X (ppm) Date CO2 400 400 400 400 (c) (g) Garmisch Garmisch Darwin Darwin 390 390 390 390 380 380 370 370 370 370 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) CO2 g-b FTS X (ppm) Date CO2 Date 400 400 400 400 (d) (h) Park Falls Park Falls Wollongong Wollongong 390 390 390 390 380 380 380 380 370 370 370 370 360 360 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) Date CO2 g-b FTS X (ppm) Date CO2 400 400 5 Fig.B1. (i) Lauder Lauder 390 390 Fig. B1. Time series of GOSAT TANSO-FTS SWIR (blue trian- gles) and g-b FTS (pink squares) X and their scatter diagrams CO 380 380 for (a) Bialystok, (b) Orleans, ´ (c) Garmisch, (d) Park Falls, (e) La- 370 370 mont, (f) Tsukuba, (g) Darwin, (h) Wollongong, and (i) Lauder. The 360 360 GOSAT data were retrieved within ±5 degrees latitude/longitude 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) Date CO2 box centered at each g-b FTS site and the g-b FTS data were the 6 Fig.B2. mean values measured within ±1 h of GOSAT overpass time. Fig. B1. Continued. Acknowledgements. We express our sincere thanks to the mem- 400 Bialyst ok bers of the NIES GOSAT project office, data algorithm team, Orleans atmospheric transport modeling team for their useful comments. Garmisch We thank Nobuyuki Kikuchi in NIES and Komei Yamaguchi in ParkFalls the Japan Weather Association for plotting the data. We would Lamont Tsukuba like to thank anonymous referees and the associated editor for Darw in improving this paper. This work was funded by the Ministry of the W ollongong Environment in Japan. We also thank NASA’s Terrestrial Ecology Lauder Program and the Orbiting Carbon Observatory for their support of TCCON, and acknowledge support from the EU within the projects GEOMON and IMECC. The Lauder TCCON measurements are funded by New Zealand Foundation for Research, Science and 360 370 380 390 400 Technology contracts CO1X0204 and CO1X0406. We thank FT S X CO2 (ppm) the members of RAMCES team at LSCE (Gif-sur-Yvette) for maintaining the FTS at the Trainou station and providing station 3 Fig.B3. Fig. B2. Scatter diagram between GOSAT and g-b FTS X at CO logistics. all FTS sites. The GOSAT data were retrieved within ±5 degrees latitude/longitude box centered at each g-b FTS site and the g-b Edited by: G. Stiller FTS data were the mean values measured within ±1 h of GOSAT overpass time. www.atmos-meas-tech.net/4/1061/2011/ Atmos. Meas. Tech., 4, 1061–1076, 2011 X (ppm) X (ppm) X (ppm) X (ppm) CO2 CO2 CO2 CO2 GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) XCO2(ppm) XCO2(ppm) XCO2(ppm) XCO2(ppm) XCO2(ppm) GOSAT SWIR X CO2 (ppm) GOSAT SWIR X (ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) CO2 1074 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1.9 1.9 1.9 1.9 (a) (e) Lamont Lamont Bialystok Bialystok 1.8 1.8 1.8 1.8 1.7 1.7 1.7 1.7 1.6 1.6 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 1.6 1.7 1.8 1.9 g-b FTS X (ppm) g-b FTS X (ppm) CH4 Date CH4 Date 2 2 1.9 1.9 1.9 1.9 (f) (b) Orleans Orleans Tsukuba Tsukuba 1.8 1.8 1.8 1.8 1.7 1.7 1.7 1.7 1.6 1.6 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 1.6 1.7 1.8 1.9 g-b FTS X (ppm) g-b FTS X (ppm) Date CH4 Date CH4 1.9 1.9 1.9 1.9 (g) (c) Garmisch Garmisch Darwin Darwin 1.8 1.8 1.8 1.8 1.7 1.7 1.7 1.7 1.6 1.6 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 1.6 1.7 1.8 1.9 g-b FTS X (ppm) g-b FTS X (ppm) CH4 Date CH4 Date 4 4 1.9 1.9 1.9 1.9 (d) (h) Park Falls Park Falls Wollongong Wollongong 1.8 1.8 1.8 1.8 1.7 1.7 1.7 1.7 1.6 1.6 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 1.6 1.7 1.8 1.9 g-b FTS X (ppm) CH4 Date g-b FTS XCH4 (ppm) Date 1.9 1.9 (i) 5 Fig.B4. Lauder Lauder Fig. B3. Time series of GOSAT TANSO-FTS SWIR (blue trian- 1.8 1.8 gles) and g-b FTS (pink squares) X and their scatter diagrams CH ´ 1.7 1.7 for (a) Bialystok, (b) Orleans, (c) Garmisch, (d) Park Falls, (e) La- mont, (f) Tsukuba, (g) Darwin, (h) Wollongong, and (i) Lauder. The 1.6 1.6 GOSAT data were retrieved within ±5 degrees latitude/longitude 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) Date CH4 box centered at each g-b FTS site and the g-b FTS data were the 6 Fig.B5. mean values measured within ±1 h of GOSAT overpass time. 21 Fig. B3. Continued. 1.9 Bialyst ok References Orleans Baker, D. F., Law, R. M., Gurney, K. R., Rayner, P., Peylin, Garmisch P., Denning, A. S., Bousquet, P., Bruhwiler, L., Chen, Y. - ParkFalls 1.8 H., Ciais, P., Fung, I. 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Preliminary validation of column-averaged volume mixing ratios of carbon dioxide and methane retrieved from GOSAT short-wavelength infrared spectra

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Atmos. Meas. Tech., 4, 1061–1076, 2011 Atmospheric www.atmos-meas-tech.net/4/1061/2011/ Measurement doi:10.5194/amt-4-1061-2011 © Author(s) 2011. CC Attribution 3.0 License. Techniques Preliminary validation of column-averaged volume mixing ratios of carbon dioxide and methane retrieved from GOSAT short-wavelength infrared spectra 1 1 1 1 1 2 3 2 2 I. Morino , O. Uchino , M. Inoue , Y. Yoshida , T. Yokota , P. O. Wennberg , G. C. Toon , D. Wunch , C. M. Roehl , 4 4 4 5 5 6 6 J. Notholt , T. Warneke , J. Messerschmidt , D. W. T. Griffith , N. M. Deutscher , V. Sherlock , B. Connor , 6 7 7 J. Robinson , R. Sussmann , and M. Rettinger National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan California Institute of Technology, Pasadena, CA, 91125-2100, USA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109-8099, USA Institute of Environmental Physics, University of Bremen, 28334 Bremen, Germany Center for Atmospheric Chemistry, University of Wollongong, New South Wales 2522, Australia National Institute of Water and Atmospheric Research, Wellington, New Zealand IMK-IFU, Karlsruhe Institute of Technology, Garmisch-Partenkirchen, Germany Received: 26 November 2010 – Published in Atmos. Meas. Tech. Discuss.: 8 December 2010 Revised: 25 April 2011 – Accepted: 19 May 2011 – Published: 15 June 2011 Abstract. Column-averaged volume mixing ratios of carbon 1 Introduction dioxide and methane retrieved from the Greenhouse gases The concentration of carbon dioxide (CO ) has increased Observing SATellite (GOSAT) Short-Wavelength InfraRed 2 from about 280 to 380 ppm over the past century due to observation (GOSAT SWIR X and X ) were compared CO CH 2 4 the burning of fossil fuels associated with expanding indus- with the reference calibrated data obtained by ground-based trial activities (IPCC, 2007). CO absorbs infrared radiation high-resolution Fourier Transform Spectrometers (g-b FTSs) 2 from the surface and hence an increase in CO concentrations participating in the Total Carbon Column Observing Net- leads to a rise in atmospheric temperature. CO and other work (TCCON). trace gases such as methane (CH ), nitrous oxide (N O), hy- 4 2 Preliminary results are as follows: the GOSAT SWIR drofluorocarbons (HFCs), perfluorocarbons (PFCs) and sul- X and X (Version 01.xx) are biased low by 8.85 CO CH 2 4 fur hexafluoride (SF ) are greenhouse gases that are subject ± 4.75 ppm (2.3 ± 1.2 %) and 20.4 ± 18.9 ppb (1.2 ± 1.1 %), to emissions regulations under the Kyoto Protocol. Together, respectively. The standard deviation of the GOSAT SWIR CO and CH account for over 80 percent of the total an- 2 4 X and X is about 1 % (1σ ) after correcting the neg- CO CH 2 4 thropogenic warming effect caused by all greenhouse gases ative biases of X and X by 8.85 ppm and 20.4 ppb, CO CH 2 4 based on the estimates of radiative forcing from 1750 to 2005 respectively. The latitudinal distributions of zonal means of (IPCC, 2007). Changes in temperature can cause feedbacks the GOSAT SWIR X and X show similar features to CO CH 2 4 that alter CO concentrations by influencing the biosphere those of the g-b FTS data except for the negative biases in (Cox et al., 2000). Methane in the atmosphere is determined the GOSAT data. by a balance between emission from the surface and loss in the soils and by OH radicals in the atmosphere. After almost a decade of near-zero growth, globally-averaged atmospheric methane increased during 2007 and 2008. The cause of this increase is not yet clear (Dlugokencky et al., 2009). To ac- curately predict future atmospheric CO and CH concentra- 2 4 tions and their impacts on climate, it is necessary to clarify Correspondence to: O. Uchino the distribution and variations of those sources and sinks. ([email protected]) Published by Copernicus Publications on behalf of the European Geosciences Union. 1062 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane Current estimates of CO flux from inverse methods rely processing such as monthly averaged X and X (Level 2 CO CH 2 4 mainly on ground-based data (Baker et al., 2006). Errors 3 products) and Level 4 carbon flux estimates. The primary in the estimation of regional fluxes from Africa and South purpose of the GOSAT is to make more accurate estimates of America are particularly large because ground-based moni- these fluxes on sub-continental scales (several hundred thou- toring stations are sparsely located in those regions. Spec- sand square kilometers) and contributing toward the broader troscopic remote sensing from space is capable of acquiring effort of environmental monitoring of ecosystem carbon bal- data that cover the globe and hence is expected to reduce ance. Further, through research using the GOSAT product, errors in the CO flux estimation using inverse modeling. new knowledge will be accumulated on the global distribu- To improve annual flux estimates on a sub-continental scale, tion of greenhouse gases and their temporal variations, as the required precision of monthly averaged column-averaged well as the global carbon cycle and its influence on climate. volume mixing ratio of carbon dioxide (X ) is less than These new findings will be utilized to improve predictions of CO ◦ ◦ 1 % on a 8 × 10 grid without biases or with uniform biases future climate change and its impacts. (Rayner and O’Brien, 2001; Houweling et al., 2004; Miller 2.2 GOSAT instruments and observation methods et al., 2007). To reduce the uncertainty in monthly, sub- continental (about 500 km) methane source strengths from Details of the GOSAT instruments have been described by satellite measurements, the precision of the column-averaged Kuze et al. (2009). GOSAT is placed in a sun-synchronous volume mixing ratios of methane is required to be 1–2 % orbit with an equator crossing time of about 13:00 local time, without systematic biases (Meirink et al., 2006). For this with an inclination angle of 98 degrees. GOSAT flies at an purpose, satellite-based data products must be validated by altitude of approximately 666 km and completes an orbit in higher-precision data obtained independently using ground- about 100 min. The spacecraft returns to observe the same based or aircraft measurements (Chahine et al., 2005; Suss- point on Earth every three days. The instruments onboard the mann et al., 2005; Dils et al., 2006; Schneising et al., 2008; satellite are TANSO-FTS and the TANSO Cloud and Aerosol Kulawik et al., 2010). Imager (TANSO-CAI). In this study, data products retrieved by the National Insti- TANSO-FTS has a Michelson interferometer that was cus- tute for Environmental Studies (NIES) from spectra obtained tom designed and built by ABB-Bomem, Quebec, Canada. by the Greenhouse gases Observing SATellite (GOSAT) are Spectra are obtained in four bands: band 1 spanning 0.758– compared with ground-based high-resolution Fourier Trans- −1 −1 0.775 μm (12 900–13 200 cm ) with 0.37 cm or better form Spectrometer (g-b FTS) data calibrated to the World spectral resolution, and bands 2–4, spanning 1.56–1.72, Meteorological Organization (WMO) scale. In Sect. 2, we 1.92–2.08, and 5.56–14.3 μm (5800–6400, 4800–5200, and present an overview of the GOSAT project, GOSAT in- −1 −1 700–1800 cm , respectively) with 0.26 cm or better spec- struments and observations, and retrievals from the GOSAT tral resolution. The TANSO-FTS instantaneous field of view Thermal And Near-infrared Sensor for carbon Observation is ∼15.8 mrad corresponding to a nadir footprint diameter Fourier Transform Spectrometer, measuring in the Short- of about 10.5 km at sea level. The nominal single-scan data Wavelength InfraRed (TANSO-FTS SWIR). Reference data acquisition time is 4 s. measured with g-b FTS are described in Sect. 3. Charac- TANSO-FTS observes solar light reflected from the earth’s teristics of GOSAT SWIR products and preliminary results surface as well as the thermal radiance emitted from the at- compared with the reference data are presented in Sect. 4, mosphere and the surface. The former (SWIR region) is ob- and the discussion and conclusions follow. served in bands 1 to 3 of the FTS in the daytime only, and the latter (Thermal InfraRed, TIR, region) is captured in band 4 during both the day and the night. The surface reflection 2 Overview of GOSAT, the GOSAT instruments, and characteristics of land and water differ significantly. The land data products retrieved from GOSAT TANSO-FTS is close to Lambertian, whereas the ocean is much more spec- SWIR observations ular. TANSO-FTS observes scattered sunlight over land us- ing a nadir-viewing observation mode, and over ocean using 2.1 GOSAT a sunglint observation mode. TANSO-CAI is a radiometer and observes the state of the GOSAT, launched on 23 January 2009, is the world’s first atmosphere and the surface during daytime. The image data satellite dedicated to measuring the atmospheric concentra- from CAI are used to determine cloud properties over an ex- tions of CO and CH from space. The GOSAT Project is 2 4 tended area that includes the FTS’ field of view as described a joint effort of the Ministry of the Environment (MOE), by Ishida and Nakajima (2009). As part of the retrieval, cloud the NIES, and the Japan Aerospace Exploration Agency characteristics and aerosol amounts are also retrieved. This (JAXA). NIES is responsible for (1) developing the retrieval information can be used to reject cloudy scenes and correct of greenhouse gas concentrations (Level 2 products) from the influence of aerosols on the retrieved X and X . CO CH 2 4 satellite and auxiliary data, (2) validating the retrieved green- house gas concentrations, and (3) producing higher-level Atmos. Meas. Tech., 4, 1061–1076, 2011 www.atmos-meas-tech.net/4/1061/2011/ I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1063 Over the three-day orbital repeat period, TANSO-FTS The column-averaged volume mixing ratio of CO (X ) 2 CO takes several tens of thousands of observations that cover or CH (X ) is defined to be the ratio of the CO (or CH ) 4 CH 2 4 the globe. Since the retrievals are limited to areas under column amount to the dry air column amount. To calculate clear sky conditions, only about ten percent of the spectra ob- the dry air column, the GFIT software uses the measured O tained by TANSO-FTS can be used for the retrieval of CO column, divided by the known dry air mole fraction of O 2 2 and CH . Nevertheless, the number of remaining data points (0.2095). The O column is measured simultaneously with 4 2 far surpasses the current number of ground monitoring sta- the CO and CH columns using the spectral band covering 2 4 tions used for analysis in the World Data Centre for Green- 1.25–1.29 μm. X and X are then obtained from: CO CH 2 4 house Gases (WDCGG), which is below 200 (WMO, 2009). X = 0.2095 (CO column/O column) CO 2 2 GOSAT serves to fill in the blanks in the ground observation network. X = 0.2095 (CH column/O column) CH 4 2 2.3 Products retrieved from GOSAT TANSO-FTS Ratioing by O minimizes systematic and correlated errors SWIR spectra present in both retrieved columns like pointing error, surface pressure uncertainty, instrument line shape uncertainty, H O The analysis of the TANSO-FTS SWIR spectra is described vapor uncertainty, zero level offsets and solar intensity vari- in detail by Yoshida et al. (2011). Briefly, absorption spec- ation (e.g. thin clouds). We use “uncertainty” as tra at bands 1 and 2 are used together to retrieve CO and 2 2 2 uncertainty = accuracy + precision CH column abundances. From all spectra observed with TANSO-FTS SWIR, only those measured without cloud in- accuracy = bias = systematic error terference are selected for further processing. Based on the absorption characteristics of each gas, the selected spectra precision = random error. are used to retrieve column abundances of CO and CH 2 4 (Level 2 product). The retrieval errors of X and X The precision of g-b FTS measurement of X is better than CO CH CO 2 4 2 are on average 2 ppm and 8 ppb or about 0.5 % respectively. 0.2 % under clear sky conditions (Washenfelder et al., 2006; The retrieval errors include TANSO-FTS SWIR measure- Ohyama et al., 2009; Wunch et al., 2011; Messerschmidt ment noise, smoothing error and interference error, and the et al., 2010). All TCCON X data are corrected for an CO main error is the measurement noise (Yoshida et al., 2011). airmass-dependent artifact (Wunch et al., 2011). Aircraft Variations in the CO concentration are most obvious near profiles obtained over many of these sites are used to deter- the surface of the earth. The CO absorption bands near mine an empirical scaling to place the TCCON data on the 1.6 μm and 2.0 μm provide information on the near-surface WMO standard reference scale. The scaling factors of X CO concentrations. On the other hand, the TIR absorption band and X are 1.011 and 1.022, respectively. The uncertainty CH around 14 μm is used to obtain information on the profiles of of X and X associated with the g-b FTS measurement CO CH 2 4 CO and CH , mainly at altitudes above 2 km (Saitoh et al., is estimated to be 0.8 ppm (∼0.2 %) and 4 ppb (∼0.2 %) by 2 4 2009). The retrievals from the TIR spectra and the validation comparing the TCCON retrievals with many different aircraft of their products will be presented in a forthcoming paper. profiles (Wunch et al., 2010). Validation of the TANSO-FTS SWIR Level 2 data prod- The g-b FTS data at nine TCCON sites are used in this uct is critical since the data are used for generating Level 3 analysis. Figure 1 shows the location of the FTS sites which and Level 4 products. GOSAT Level 2 products are evalu- are used in the present study. FTS sites are located in Asia, ated against high-precision data obtained independently us- Oceania, Europe, and North America. Table 1 summarizes ing ground-based or aircraft observations. Here we com- the spatial coordinates of those stations. pare the GOSAT SWIR X and X results with those CO CH 2 4 data obtained with ground-based high-resolution FTSs (g-b 4 Results of initial validation FTSs). 4.1 GOSAT product selection for validation 3 Reference data for GOSAT product validation The GOSAT SWIR X and X products used here are CO CH 2 4 Ver.01.xx. The retrieval algorithm for Ver.01.xx uses band 1 Spectra measured with g-b FTS are analyzed using the GFIT −1 −1 (12 900–13 200 cm ) and band 2 (5800–6400 cm ) to si- nonlinear least squares spectral fitting algorithm developed multaneously estimate X and X . In addition, the wa- CO CH at the Jet Propulsion Laboratory (Toon et al., 1992; Wunch 2 4 ter vapor column and aerosol optical depth (AOD) at a wave- et al., 2011), which is used for retrievals across all stations length of 1.6 μm are retrieved. Band 3 is used for selecting that comprise the Total Carbon Column Observing Network scenes with cirrus clouds which CAI can not detect (Yoshida (TCCON; Wunch et al., 2011). Here, we use the GFIT 7 Mar et al., 2011). Table 2 summarizes the spectral line parame- 2009 release. ters of CO , CH , H O and O molecules and the parameters 2 4 2 2 www.atmos-meas-tech.net/4/1061/2011/ Atmos. Meas. Tech., 4, 1061–1076, 2011 1064 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane Table 1. Ground-based FTS sites used for GOSAT product validation. Site Country Coordinate [Lat., Long.] Alt. [m a.s.l.] Reference ◦ ◦ Bialystok Poland 53.23 N, 23.0253 E 180 Messerschmidt et al. (2010) ◦ ◦ Orleans ´ France 47.965 N, 2.11253 E 130 Messerschmidt et al. (2010) ◦ ◦ Garmisch Germany 47.476 N, 11.0633 E 746.6 Sussmann et al. (2009) ◦ ◦ Park Falls USA 45.945 N, 90.2733 W 442 Washenfelder et al. (2006) ◦ ◦ Lamont USA 36.604 N, 97.4863 W 320 Wunch et al. (2010, 2011) ◦ ◦ Tsukuba Japan 36.0513 N, 140.12153 E 31 Ohyama et al. (2009) ◦ ◦ Darwin Australia 12.424453 S, 130.891543 E 32 Deutscher et al. (2010) ◦ ◦ Wollongong Australia 34.40633 S, 150.8793 E 30 ◦ ◦ Lauder New Zealand 45.03843 S, 169.6843 E 370 1 (a) 2 Fig.1. Fig. 1. Ground-based FTS sites used for the GOSAT product vali- dation in the present study. 4 (b) retrieved from bands 1 and 2 of TANSO-FTS. The grid point values of the meteorological data analyzed by the Japan Me- teorological Agency are interpolated to the retrieval points. The X and X data shown here (general public users, CO CH 2 4 or GU subset) are filtered for AOD less than 0.5. As a plane- parallel atmosphere is assumed in the retrieval, data with so- lar zenith angles greater than 70 degrees are not processed, and data over high mountain ranges such as the Rockies, the 18 Andes, and the Himalayan mountains are removed. 19 6 Fig.2. 20 7 Fig. 2. Global distribution of GOSAT SWIR X averaged 4.2 Global distribution of X and X CO CH CO 2 4 monthly in 1.5 by 1.5 degree bins for (a) April and (b) October 22 9 in 2009. 23 Figures 2 and 3 show the global distribution of the monthly- 10 24 11 averaged GOSAT SWIR X and X data, gridded in CO CH 2 4 25 ◦ ◦ 1.5 by 1.5 bins in April and October 2009, respectively. X is observed in both hemispheres. The standard devi- 26 CO 2 2 These retrievals satisfy the filter criteria over North Africa, ◦ ◦ ations of monthly mean X is about 1 % for a 10 × 10 CO the Arabian Peninsula, and Australia. Data over land are ob- grid over Australia, where gradients are anticipated to be ◦ ◦ tained mainly for 10–60 N and 15–45 S in April, and 10– very small. ◦ ◦ 50 N and 0–50 S in October. Data over ocean are retrieved X in the Northern Hemisphere is higher than in CH ◦ ◦ ◦ ◦ 4 in the regions of 10 S–30 N in April and 40 S–10 N in the Southern Hemisphere in both April and October 2009 October by observing the specular reflection of sunlight in (Fig. 3). Elevated X is observed from India to Japan in CH the direction of sunglint. October 2009. These features are similar to those obtained X in April is generally higher in the Northern Hemi- CO by SCIAMACHY (Frankenberg et al., 2006) and simulated sphere than the Southern Hemisphere (Fig. 2). This is be- by an inversion model (Bergamaschi et al., 2007). cause plant photosynthesis in the Northern Hemisphere is not yet competitive with respiration in April. In October, similar Atmos. Meas. Tech., 4, 1061–1076, 2011 www.atmos-meas-tech.net/4/1061/2011/ I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1065 Table 2. (a) Spectroscopic databases of CO , CH , H O and O molecules and (b) parameters retrieved from bands 1 and 2 of the TANSO 2 4 2 2 FTS in the Ver.01.xx. (a) Spectroscopic database Reference CO Voigt + Line mixing Lamouroux et al. (2010) CH Voigt HITRAN 2008 H O Voigt HITRAN 2008 O Voigt + Line mixing and collision-induced absorption Tran et al. (2006); Tran and Hartmann (2008) (b) Land surface albedo CO CH H O AOD surface press. temp. profile bias wavenumber dispersion 2 4 2 Ocean surface wind speed radiance adjust. factor 1 (a) GOSAT data are selected within about 0.5 to 1.5 degrees rect- angular area centered at each FTS site depending on the geo- graphical distribution of land and sea. As much as possible, we used only the GOSAT data retrieved over flat land. 4.3.1 X CO The time series of the GOSAT and g-b FTS data for X are CO shown on the left and their scatter diagrams on the right in Fig. 4. In the scatter diagram, we plotted data when g-b FTS data were collected within ±30 min of the GOSAT overpass time and corresponding GOSAT X values were success- CO fully retrieved. Therefore, the number of the GOSAT data in 4 (b) the scatter diagram is less than that in the time series. Only a few GOSAT data are available for comparison with Bia- lystok, Garmisch, Park Falls and Lauder. Darwin FTS data were not obtained from May 2010 through September 2010 due to mechanical problems with the sun tracker. X re- CO trieved from GOSAT SWIR measured near Orleans, ´ Lamont and Tsukuba sites are higher in boreal spring and lower in au- tumn (Fig. 4b, e, and f). A clear seasonality over the Northern Hemisphere can also be seen in the maps in Fig. 2. In con- trast, the seasonal variation of g-b FTS X in the Southern CO Hemisphere (i.e., Darwin, Wollongong, and Lauder) is weak 6 Fig.3. (Fig. 4g, h, and i) as expected due to smaller contribution of Fig. 3. Global distribution of GOSAT SWIR X averaged CH the continents. monthly in 1.5 by 1.5 degree bins for (a) April and (b) October Figure 5 shows the scatter diagram between the GOSAT in 2009. data and the g-b FTS data for all sites, and the slope of the regression line with no intercept is 0.977 with a corre- lation coefficient of 0.378 and Table 3 summarizes the dif- 4.3 Comparisons between g-b FTS data and GOSAT ference of the GOSAT data to the g-b FTS data at each site. TANSO-FTS SWIR data The difference of the GOSAT data to the g-b FTS data is GOSAT TANSO-FTS SWIR data are compared with the g-b −8.85 ± 4.75 ppm or −2.3 ± 1.2 %. FTS data at 9 TCCON sites (Fig. 1). We illustrate here the time series of the TANSO-FTS SWIR Level 2 data and g-b 4.3.2 X CH FTS data and their scatter diagrams for X and X . The CO CH 2 4 g-b FTS data are the mean values and standard deviations The time series of the GOSAT and g-b FTS data for X CH (1 σ ) measured at each FTS site within ±30 min of GOSAT are shown on the left and their scatter diagrams on the right overpass time (at most sites, around 13:00 local time). The in Fig. 6. The bias of X is smaller than that of X . CH CO 4 2 www.atmos-meas-tech.net/4/1061/2011/ Atmos. Meas. Tech., 4, 1061–1076, 2011 1066 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 400 400 (a) Table 3. Left side: the average and one standard deviation (1σ ) Bialystok Bialystok 390 390 of the difference between GOSAT X and g-b FTS X for CO CO 2 2 the nine TCCON sites. Right side: the average and one standard 380 380 deviation (1σ ) of the difference normalized to g-b FTS X (given CO 370 370 in percent). Note that the number of data listed here indicates the 360 360 count of valid cases in which g-b FTS data were collected within 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 Date g-b FTS X (ppm) CO2 ±30 min of the GOSAT overpass time and corresponding GOSAT 400 400 (b) Orleans Orleans X values were successfully retrieved. CO 390 390 380 380 Sites (GOSAT SWIR X ) – [(GOSAT SWIR X ) – CO CO 2 2 370 370 (g-b FTS X ) (g-b FTS X )]/ CO CO 2 2 (g-b FTS X ) CO 2 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 Number Average 1σ Average 1σ g-b FTS X (ppm) Date CO2 400 400 (c) of data (ppm) (ppm) (%) (%) Garmisch Garmisch 390 390 Bialystok 1 5.01 – 1.32 – Orleans ´ 14 −12.85 3.79 −3.33 0.99 380 380 Garmisch 3 −7.78 3.78 −2.00 0.96 370 370 Park Falls 1 −6.05 – −1.58 – Lamont 11 −10.31 4.80 −2.65 1.23 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 Tsukuba 13 −6.38 2.75 −1.64 0.71 g-b FTS X (ppm) Date CO2 400 400 Darwin 6 −6.09 2.61 −1.58 0.68 (d) Park Falls Park Falls Wollongong 11 −8.77 4.74 −2.28 1.23 390 390 Lauder 2 −7.45 0.15 −1.94 0.04 380 380 All data 62 −8.85 4.75 −2.29 1.23 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) Date CO2 5 Fig.4. Table 4. As in Table 3 except for X . CH Fig. 4. Time series of GOSAT TANSO-FTS SWIR (blue triangles) and g-b FTS (pink squares) X and their scatter diagrams for (a) CO Sites (GOSAT SWIR X ) – [(GOSAT SWIR X ) – 2 CH CH 4 4 Bialystok, (b) Orleans, ´ (c) Garmisch, (d) Park Falls, (e) Lamont, (f) (g-b FTS X ) (g-b FTS X )]/ CH CH 4 4 (g-b FTS X ) Tsukuba, (g) Darwin, (h) Wollongong, and (i) Lauder. CH Number Average 1σ Average 1σ of data (ppm) (ppm) (%) (%) 4.3.3 Remarks and relaxed coincidence criteria Bialystok 1 0.0227 – 1.29 – Orleans ´ 14 −0.0367 0.0178 −2.06 1.00 Garmisch 3 −0.0114 0.0160 −0.64 0.90 There are too few data points in Tables 3 and 4 to compute Park Falls 1 −0.0120 – −0.66 – meaningful statistics. For statistical significance, we have to Lamont 11 −0.0230 0.0181 −1.28 1.01 consider all the data (62) in Tables 3 and 4. For Orleans, ´ La- Tsukuba 13 −0.0120 0.0115 −0.67 0.64 Darwin 6 −0.0080 0.0089 −0.46 0.51 mont, Tsukuba and Wollongong, where there are more than Wollongong 11 −0.0235 0.0190 −1.34 1.08 10 coincident data points in Table 3, site-dependent biases Lauder 2 −0.0067 0.0003 −0.39 0.01 are the same within the mutual standard deviations. How- All data 62 −0.0204 0.0189 −1.15 1.06 ever, this is a topic for further investigation. We relaxed the coincidence criteria. Comparison of the GOSAT data retrieved within ±2 and ±5 degrees latitude/longitude box centered at each g-b FTS site and the In Lamont and Orleans, ´ X levels obtained from GOSAT CH mean values of the g-b FTS data measured within ±1 h of SWIR are higher in boreal autumn. The g-b FTS data of GOSAT overpass time can be found in Appendixes A and X over Tsukuba have a peak in summer rather than au- CH 4 B. For ±2 degree latitude/longitude, the GOSAT X and CO tumn. X are biased low by 8.57 ± 4.44 ppm (2.2 ± 1.2 %) and CH Figure 7 shows the scatter diagram between the GOSAT 15.8 ± 22.3 ppb (0.89 ± 1.26 %), respectively. For ±5 degree data and the g-b FTS data for all sites. The slope of the latitude/longitude, the GOSAT X and X are biased CO CH 2 4 regression line with no intercept is 0.998 and the correla- low by 8.25 ± 3.97 ppm (2.1 ± 1.0 %) and 14.8 ± 22.6 ppb tion coefficient is 0.681. The difference between the GOSAT (0.83 ± 1.27 %), respectively. These results are nearly equal data and the g-b FTS data at each site is shown in Table 4. to those in Tables 3 and 4. For these relaxed coincidence cri- The difference of the GOSAT data to the g-b FTS data is teria, site-dependent biases of the GOSAT X and X CO CH 2 4 −20.4 ± 18.9 ppb or −1.2 ± 1.1 %. are also the same within the mutual standard deviations Atmos. Meas. Tech., 4, 1061–1076, 2011 www.atmos-meas-tech.net/4/1061/2011/ X (ppm) X (ppm) XCO2 (ppm) X (ppm) CO2 CO2 CO2 GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) CO2 CO2 CO2 CO2 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1067 1 1 400 400 1.9 1.9 (e) (a) Lamont Lamont Bialystok Bialystok 390 390 1.8 1.8 380 380 1.7 1.7 370 370 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) Date g-b FTS X (ppm) Date CO2 CH4 2 2 400 400 1.9 1.9 (f) (b) Orleans Orleans Tsukuba Tsukuba 390 390 1.8 1.8 380 380 1.7 1.7 370 370 360 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 Date g-b FTS XCO2 (ppm) Date g-b FTS XCH4 (ppm) 3 3 400 400 1.9 1.9 (g) (c) Darwin Darwin Garmisch Garmisch 1.8 1.8 1.7 1.7 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) g-b FTS X (ppm) Date CO2 Date CH4 4 4 400 400 1.9 1.9 (h) (d) Wollongong Wollongong Park Falls Park Falls 390 390 1.8 1.8 380 380 1.7 1.7 370 370 360 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 Date g-b FTS XCO2 (ppm) Date g-b FTS XCH4 (ppm) 400 400 (i) 5 Fig.7. Lauder Lauder 390 390 Fig. 6. Time series of GOSAT TANSO-FTS SWIR (blue triangles) 380 380 and g-b FTS (pink squares) X and their scatter diagrams for (a) CH Bialystok, (b) Orleans, (c) Garmisch, (d) Park Falls, (e) Lamont, (f) 370 370 Tsukuba, (g) Darwin, (h) Wollongong, and (i) Lauder. 360 360 10 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS XCO (ppm) Date 2 6 Fig.5. because the standard deviations of the biases are large at re- Fig. 4. Continued. 5 specti ve FTS sites. However, the peak-to-peak variation of the biases from site to site is now 1.2–1.8 %. We have to Bialystok 400 investigate further to decrease the variation of the biases. Orleans Garmisch 4.4 Latitudinal distributions of zonal averaged GOSAT ParkFalls SWIR X and X CO CH 2 4 Lamont Tsukuba In Sect. 4.3, g-b FTS data recorded within ±30 min of the Darwin GOSAT overpass were used for the validation. To obtain larger numbers of samples and depict the latitudinal features, Wollongong we calculated monthly mean X and X of g-b FTS Lauder CO CH 2 4 data obtained within ±30 min of the time when GOSAT is supposed to overpass for all days, including the days when GOSAT does not overpass each site. In addition, monthly 360 370 380 390 400 mean values of zonal averaged GOSAT data, based on all FTS X (ppm) CO 2 data obtained, are calculated in each 15 degree latitudinal band. 3 Fig.6. Fig. 5. Scatter diagram between GOSAT TANSO-FTS SWIR and Latitudinal distributions of monthly means of zonal aver- g-b FTS X at all FTS sites. CO aged GOSAT SWIR and g-b FTS data of X in April and 2 CO October 2009 are shown in Fig. 8. Both data sets show that X is higher in the Northern Hemisphere compared with CO 7 the Southern Hemisphere in April and the difference between www.atmos-meas-tech.net/4/1061/2011/ Atmos. Meas. Tech., 4, 1061–1076, 2011 GOSAT SWIR X CO2 (ppm) X (ppm) X (ppm) X (ppm) X (ppm) X (ppm) CO2 CO2 CO2 CO2 CO2 GOSAT SWIR XCO2 (ppm) GOSAT SWIR XCO2 (ppm) GOSAT SWIR XCO2 (ppm) GOSAT SWIR XCO2 (ppm) GOSAT SWIR XCO2 (ppm) X (ppm) X (ppm) X (ppm) X (ppm) CH4 CH4 CH4 CH4 GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) CH4 CH4 CH4 CH4 1068 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1.9 1.9 (e) Lamont Lamont 1.9 Bialystok 1.8 1.8 Orleans Garmisch 1.7 1.7 ParkFalls 1.8 Lamont 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) Date CH4 Tsukuba 1.9 1.9 (f) Tsukuba Tsukuba Darwin Wollongong 1.8 1.8 1.7 Lauder 1.7 1.7 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 1.6 g-b FTS X (ppm) Date CH4 1.9 1.9 1.6 1.7 1.8 1.9 (g) Darwin Darwin FTS X (ppm) CH4 1.8 1.8 1.7 1.7 3 Fig.9. Fig. 7. Scatter diagram between GOSAT TANSO-FTS SWIR and g-b FTS X at all FTS sites. CH 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 Date g-b FTS X (ppm) CH4 1.9 1.9 (h) Wollongong Wollongong reduced compared with earlier versions of the retrievals 1.8 1.8 (Yokota et al., 2009). The earlier versions (Ver.00.yy) used 1.7 1.7 only band 2 of TANSO-FTS and retrieved CO and CH 2 4 columns separately and estimates X and X using a CO CH 2 4 1.6 1.6 10 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 dry-air column calculated from meteorological data analyzed Date g-b FTS XCH4 (ppm) by the Japan Meteorological Agency. Over the Sahara Desert 1.9 1.9 (i) Lauder Lauder and Arabian Peninsula and their surrounding areas, appar- 1.8 1.8 ent high values of X and X were retrieved due to CO CH 2 4 14 the influences of dust particles. In Ver.01.xx released in Au- 1.7 1.7 gust 2010, bands 1 and 2 of TANSO-FTS were used for si- 1.6 1.6 multaneous retrieval of CO and CH columns with surface 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 2 4 Date g-b FTS XCH4 (ppm) pressure. Therefore, the apparent high values of X and CO 6 Fig.8. X almost disappeared over the Sahara Desert and their CH Fig. 6. Continued. surrounding areas thanks to the correction of the extended optical paths by the elevated dust particles. However, bias due to aerosols and thin cirrus clouds the hemispheres is small in October. The difference of X CO still exists because of the anomalously low X retrievals CO between April and October is about 5 ppm in the northern (Fig. 2). In the future, we plan to investigate interferences mid latitudes for both data sets. The zonal means of GOSAT by aerosols and thin cirrus clouds using aerosol lidars and/or data are reasonably consistent with those of the reference val- sky-radiometers at selected FTS sites. ues, apart from the overall biases. The negative bias of about 9 ppm or 2.3 % in the GOSAT Figure 9 shows latitudinal distributions of monthly means TANSO-FTS SWIR data of X is not still understood. CO of zonal averaged GOSAT SWIR and g-b FTS data of X CH It may result from unknown spectroscopic parameters of for April and October 2009. X is characterized by rel- CH O and CO or error in the TANSO-FTS calibration. In 2 2 atively high concentrations in the Northern Hemisphere in the case of the GOSAT SWIR data of X , the negative CH April and October. Moreover, the bias is smaller than that bias decreased in the Ver.01.xx compared with the earlier of X . In particular, the concentration of X of GOSAT CO CH 2 4 Ver.00.yy when the spectroscopic parameters were changed data is in good agreement with that of g-b FTS sites in April. from Lyulin et al. (2009) to HITRAN 2008 database (Roth- Both X data in October show a similar distribution. CH man et al., 2009). Therefore it is important to further exam- ine the spectroscopic parameters of O , CO and CH . 2 2 4 Some instrumental issues occurred since the launch of 5 Discussion GOSAT, which could also contribute to the biases. The sam- In this study, we validated the GOSAT TANSO-FTS SWIR pling laser wavelength of TANSO-FTS shifted in time prob- X and X against the TCCON g-b FTS instruments. ably due to the change of the 1.31-μm distributed-feedback CO CH 2 4 In Ver.01.xx, the influence of aerosols has been markedly laser cavity length. The sensitivity of band 1 decreased after Atmos. Meas. Tech., 4, 1061–1076, 2011 www.atmos-meas-tech.net/4/1061/2011/ XCH4 (ppm) XCH4 (ppm) XCH4 (ppm) XCH4 (ppm) XCH4 (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR XCH4 (ppm) CH4 CH4 CH4 CH4 GOSAT SWIR X (ppm) CH4 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1069 3 Fig. 9. As Fig. 8 but for X . CH Fig. 8. Latitudinal distributions of monthly means of zonal aver- 6 Fig.11. and X . This could decrease the standard deviation of the CH aged GOSAT X for each 15 latitudinal band in April and Oc- CO GOSAT X and X . To what extent topographies sur- 6 Fig.10. CO CH 2 4 tober 2009 (blue triangles). The monthly means of g-b FTS data rounding g-b FTS sites influence the data quality, is not clear observed during local time of about 12:30–13:30 hour are shown at present. We will investigate this effect in the near future. by pink squares. Vertical bars indicate the standard deviation. 6 Conclusions the launch. These effects are corrected before retrieving The GOSAT TANSO-FTS SWIR data of X and X CO CH 2 4 X and X . A TANSO-FTS pointing error occurred CO CH in the Version 01.xx were compared against reference 2 4 when the pointing mirror was moved largely to the along- data obtained with the TCCON g-b FTS sites. The track direction. This error causes the mismatch of the field GOSAT TANSO-FTS SWIR X and X were biased CO CH 2 4 of views between CAI and TANSO-FTS, and misleads the low by 8.85 ± 4.75 ppm (2.3 ± 1.2 %) and 20.4 ± 18.9 ppb cloud screening algorithm. However, in the case of the spe- (1.2 ± 1.1 %) respectively versus the reference values. The cial point observation mode of TANSO-FTS to g-b FTS sites, standard deviation of the GOSAT SWIR X and X CO CH 2 4 the mismatch should be small. retrievals is considered to be about 1 % (1 σ ) after correcting the negative biases by 8.85 ppm and 20.4 ppb, respectively. The standard deviation of the GOSAT SWIR X and CO Although X is underestimated by approximately X is about 1 % (1 σ ) after correcting the negative biases CO CH 2 9 ppm, the GOSAT retrievals and g-b FTS data show simi- by 8.85 ppm and 20.4 ppb, respectively, and it is larger than lar seasonal behaviors over the Northern Hemisphere: higher those of the g-b FTS data (∼0.2 %). The retrieval errors of in spring and lower in autumn. The latitudinal distribution X and X are on average 2 ppm and 8 ppb or about CO CH 2 4 of zonal averaged GOSAT SWIR X and X is broadly 0.5 % respectively. This means that the other errors of about CO CH 2 4 consistent with that of the g-b FTS except for the larger nega- 0.5 % are due to influences of factors such as aerosols and tive biases in the GOSAT data. We plan further studies to ad- thin cirrus clouds. In the retrieval algorithm of Ver.01.xx, dress the negative bias of the GOSAT SWIR X and X aerosols are assumed to exist homogeneously below 2-km al- CO CH 2 4 as well as to better understand the influence of aerosols and titude. In the near future retrieval algorithm, the vertical pro- thin cirrus clouds. files of aerosols will be simultaneously retrieved with X CO www.atmos-meas-tech.net/4/1061/2011/ Atmos. Meas. Tech., 4, 1061–1076, 2011 1070 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane Table A1. Left side: the average and one standard deviation (1σ ) Table A2. As in Table A1 except for X . CH of the difference between GOSAT X and g-b FTS X for CO CO 2 2 the nine TCCON sites. Right side: the average and one standard deviation (1σ ) of the difference normalized to g-b FTS X (given Sites (GOSAT SWIR X ) – [(GOSAT SWIR X ) – CH CH CO 2 4 4 (g-b FTS X ) (g-b FTS X )]/ in percent). The GOSAT data were retrieved within ±2 degrees CH CH 4 4 (g-b FTS X ) CH latitude/longitude box centered at each g-b FTS site and the g-b Number Average 1σ Average 1σ FTS data were the mean values measured within ±1 h of GOSAT of data (ppm) (ppm) (%) (%) overpass time. Bialystok 3 −0.0107 0.0306 −0.61 1.73 Orleans ´ 18 −0.0383 0.0191 −2.14 1.07 Garmisch 3 −0.0111 0.0170 −0.62 0.95 Sites (GOSAT SWIR X ) – [(GOSAT SWIR X ) – CO CO 2 2 Park Falls 14 −0.0116 0.0213 −0.65 1.19 (g-b FTS X ) (g-b FTS X )]/ CO CO 2 2 Lamont 126 −0.0108 0.0213 −0.60 1.18 (g-b FTS X ) CO Tsukuba 23 −0.0101 0.0135 −0.57 0.75 Number Average 1σ Average 1σ Darwin 9 −0.0153 0.0141 −0.87 0.80 of data (ppm) (ppm) (%) (%) Wollongong 57 −0.0237 0.0243 −1.36 1.39 Lauder 3 −0.0170 0.0179 −0.98 1.03 Bialystok 3 −6.68 10.04 −1.72 2.61 Orleans ´ 18 −13.01 3.59 −3.37 0.93 All data 256 −0.0158 0.0223 −0.89 1.26 Garmisch 3 −7.71 3.24 −1.98 0.82 Park Falls 14 −7.72 4.11 −1.99 1.06 Lamont 126 −8.28 3.88 −2.13 1.00 Tsukuba 23 −6.09 2.77 −1.57 0.71 400 400 (a) Bialystok Bialystok Darwin 9 −7.83 3.39 −2.03 0.88 390 390 Wollongong 57 −9.24 5.38 −2.39 1.39 Lauder 3 −9.70 3.86 −2.52 0.99 380 All data 256 −8.57 4.44 −2.21 1.15 370 370 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS XCO2 (ppm) Date 400 400 (b) Orleans Orleans 390 390 Appendix A 380 380 Comparison of GOSAT and g-b FTS data within ±2 degrees and ±1 h 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) CO2 Date 400 400 We performed comparison of the GOSAT data retrieved (c) Garmisch Garmisch within ±2 degrees latitude/longitude box centered at each g- 390 390 b FTS site and the mean values of the g-b FTS data measured 380 380 within ±1 h of GOSAT overpass time. 370 370 The time series of the GOSAT and g-b FTS data for X CO are shown on the left and their scatter diagrams on the right 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) CO2 Date in Fig. A1. Figure A2 shows the scatter diagram between 400 400 (d) Park Falls Park Falls the GOSAT data and the g-b FTS data for all sites, and the 390 390 slope of the regression line with no intercept is 0.978 with 380 380 a correlation coefficient of 0.319 and Table A1 summarizes 370 370 the difference of the GOSAT data to the g-b FTS data at each 360 360 site. The difference of the GOSAT data to the g-b FTS data 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) Date CO2 is −8.57 ± 4.44 ppm or −2.2 ± 1.2 %. 5 Fig.A1. The time series of the GOSAT and g-b FTS data for X CH Fig. A1. Time series of GOSAT TANSO-FTS SWIR (blue trian- are shown on the left and their scatter diagrams on the right gles) and g-b FTS (pink squares) X and their scatter diagrams CO in Fig. A3. Figure A4 shows the scatter diagram between the for (a) Bialystok, (b) Orleans, ´ (c) Garmisch, (d) Park Falls, (e) La- GOSAT data and the g-b FTS data for all sites. The slope of mont, (f) Tsukuba, (g) Darwin, (h) Wollongong, and (i) Lauder. The the regression line with no intercept is 0.991 and the correla- GOSAT data were retrieved within ±2 degrees latitude/longitude tion coefficient is 0.794. The difference between the GOSAT box centered at each g-b FTS site and the g-b FTS data were the data and the g-b FTS data at each site is shown in Table A2. mean values measured within ±1 h of GOSAT overpass time. The difference of the GOSAT data to the g-b FTS data is −15.8 ± 22.3 ppb or −0.89 ± 1.3 %. Atmos. Meas. Tech., 4, 1061–1076, 2011 www.atmos-meas-tech.net/4/1061/2011/ X (ppm) X (ppm) X (ppm) X (ppm) CO2 CO2 CO2 CO2 GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1071 400 400 1.9 1.9 (e) (a) Lamont Lamont Bialystok Bialystok 390 390 1.8 1.8 380 380 1.7 1.7 370 370 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS XCO2 (ppm) g-b FTS X (ppm) Date CH4 Date 400 400 1.9 1.9 (f) (b) Tsukuba Tsukuba Orleans Orleans 390 390 1.8 1.8 1.7 1.7 370 370 360 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) g-b FTS X (ppm) Date CO2 Date CH4 3 3 400 400 1.9 1.9 (g) (c) Darwin Darwin Garmisch Garmisch 390 390 1.8 1.8 380 380 1.7 1.7 370 370 360 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) g-b FTS XCH4 (ppm) CO2 Date Date 1.9 1.9 400 400 (d) (h) Park Falls Park Falls Wollongong Wollongong 390 390 1.8 1.8 1.7 1.7 370 370 1.6 1.6 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS XCH4(ppm) g-b FTS X (ppm) Date Date CO2 400 400 5 Fig.A4. (i) Lauder Lauder 390 390 Fig. A3. Time series of GOSAT TANSO-FTS SWIR (blue trian- gles) and g-b FTS (pink squares) X and their scatter diagrams 380 380 CH for (a) Bialystok, (b) Orleans, ´ (c) Garmisch, (d) Park Falls, (e) La- 370 370 mont, (f) Tsukuba, (g) Darwin, (h) Wollongong, and (i) Lauder. The GOSAT data were retrieved within ±2 degrees latitude/longitude 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS XCO2 (ppm) Date box centered at each g-b FTS site and the g-b FTS data were the 6 Fig.A2. mean values measured within ±1 h of GOSAT overpass time. Fig. A1. Continued. 13 400 Bialyst ok Orleans Garmisch ParkFalls Lamont Appendix B Tsukuba Darw in Comparison of GOSAT and g-b FTS data within W ollongong ±5 degrees and ±1 h 370 Lauder We performed comparison of the GOSAT data retrieved 360 within ±5 degrees latitude/longitude box centered at each g- 360 370 380 390 400 b FTS site and the mean values of the g-b FTS data measured FT S X CO2 (ppm) within ±1 h of GOSAT overpass time. The time series of the GOSAT and g-b FTS data for X CO 3 Fig.A3. Fig. A2. Scatter diagram between GOSAT and g-b FTS X at CO are shown on the left and their scatter diagrams on the right all FTS sites. The GOSAT data were retrieved within ±2 degrees in Fig. B1. latitude/longitude box centered at each g-b FTS site and the g-b Figure B2 shows the scatter diagram between the GOSAT FTS data were the mean values measured within ±1 h of GOSAT data and the g-b FTS data for all sites, and the slope of overpass time. 8 the regression line with no intercept is 0.979 with a corre- lation coefficient of 0.285 and Table B1 summarizes the dif- ference of the GOSAT data to the g-b FTS data at each site. www.atmos-meas-tech.net/4/1061/2011/ Atmos. Meas. Tech., 4, 1061–1076, 2011 XCO2(ppm) XCO2(ppm) XCO2(ppm) XCO2(ppm) X (ppm) CO2 GOSAT SWIR X CO2 (ppm) GOSAT SWIR X (ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) CO2 X (ppm) X (ppm) X (ppm) X (ppm) CH4 CH4 CH4 CH4 GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) CH4 CH4 CH4 CH4 1072 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1.9 1.9 (e) Lamont Lamont Table B1. Left side: the average and one standard deviation (1σ ) of the difference between GOSAT X and g-b FTS X for CO CO 1.8 1.8 2 2 the nine TCCON sites. Right side: the average and one standard 1.7 1.7 deviation (1σ ) of the difference normalized to g-b FTS X (given CO in percent). The GOSAT data were retrieved within ±5 degrees 1.6 1.6 latitude/longitude box centered at each g-b FTS site and the g-b 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) Date CH4 2 FTS data were the mean values measured within ±1 h of GOSAT 1.9 1.9 (f) Tsukuba Tsukuba overpass time. 1.8 1.8 1.7 1.7 Sites (GOSAT SWIR X ) – [(GOSAT SWIR X ) – CO CO 2 2 (g-b FTS X ) (g-b FTS X )]/ CO CO 2 2 1.6 1.6 (g-b FTS X ) CO 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) Date CH4 3 Number Average 1σ Average 1σ 1.9 1.9 (g) Darwin Darwin of data (ppm) (ppm) (%) (%) 1.8 1.8 Bialystok 26 −6.76 4.38 −1.75 1.13 Orleans ´ 59 −10.24 3.75 −2.65 0.97 1.7 1.7 Garmisch 15 −6.58 2.35 −1.71 0.60 Park Falls 104 −8.24 4.07 −2.13 1.05 1.6 1.6 Lamont 513 −8.29 3.60 −2.14 0.92 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) CH4 Date Tsukuba 29 −5.61 3.33 −1.44 0.86 1.9 1.9 (h) Wollongong Wollongong Darwin 72 −7.41 3.04 −1.92 0.79 Wollongong 143 −8.72 5.22 −2.26 1.35 1.8 1.8 Lauder 5 −7.02 4.57 −1.83 1.18 1.7 1.7 All data 966 −8.25 3.97 −2.10 1.02 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 Date g-b FTS XCH4 (ppm) 1.9 1.9 (i) Lauder Lauder Table B2. As in Table B1 except for X . CH 1.8 1.8 Sites (GOSAT SWIR X ) – [(GOSAT SWIR X ) – 1.7 1.7 CH CH 4 4 (g-b FTS X ) (g-b FTS X )]/ CH CH 4 4 (g-b FTS X ) 1.6 1.6 CH 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS XCH4(ppm) Date Number Average 1σ Average 1σ 6 Fig.A5. of data (ppm) (ppm) (%) (%) Fig. A3. Continued. Bialystok 26 −0.0072 0.0238 −0.41 1.35 Orleans ´ 59 −0.0230 0.0183 −1.29 1.03 Garmisch 15 0.0032 0.0152 0.18 0.85 1.9 Bialyst ok Park Falls 104 −0.0166 0.0225 −0.92 1.25 Orleans Lamont 513 −0.0132 0.0230 −0.73 1.28 Garmisch Tsukuba 29 −0.0077 0.0165 −0.43 0.92 Darwin 72 −0.0140 0.0123 −0.80 0.70 ParkFalls 1.8 Wollongong 143 −0.0218 0.0253 −1.25 1.45 Lamont Lauder 5 −0.0030 0.0230 −0.17 1.33 Tsukuba Darw in All data 966 −0.0148 0.0226 −0.83 1.27 W ollongong 1.7 Lauder The difference of the GOSAT data to the g-b FTS data is 1.6 −8.25 ± 3.97 ppm or −2.1 ± 1.0 %. 1.6 1.7 1.8 1.9 FT S X CH4 (ppm) The time series of the GOSAT and g-b FTS data for X CH are shown on the left and their scatter diagrams on the right 3 Fig.A6. Fig. A4. Scatter diagram between GOSAT and g-b FTS X at CH in Fig. B3. Figure B4 shows the scatter diagram between the all FTS sites. The GOSAT data were retrieved within ±2 degrees GOSAT data and the g-b FTS data for all sites. The slope of latitude/longitude box centered at each g-b FTS site and the g-b the regression line with no intercept is 0.992 and the correla- FTS data were the mean values measured within ±1 h of GOSAT tion coefficient is 0.712. The difference between the GOSAT overpass time. data and the g-b FTS data at each site is shown in Table B2. The difference of the GOSAT data to the g-b FTS data is −14.8 ± 22.6 ppb or −0.83 ± 1.3 %. Atmos. Meas. Tech., 4, 1061–1076, 2011 www.atmos-meas-tech.net/4/1061/2011/ X (ppm) X (ppm) X (ppm) X (ppm) CH4 CH4 CH4 CH4 X (ppm) CH4 GOSAT SWIR X CH4 (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) GOSAT SWIR X (ppm) CH4 CH4 CH4 CH4 CH4 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1073 400 400 400 400 (a) (e) Bialystok Bialystok Lamont Lamont 390 390 390 390 380 380 380 380 370 370 370 370 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) Date CO2 g-b FTS X (ppm) CO2 Date 400 400 (b) 400 400 (f) Orleans Orleans Tsukuba Tsukuba 390 390 390 390 380 380 370 370 360 360 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS XCO2 (ppm) Date g-b FTS X (ppm) Date CO2 400 400 400 400 (c) (g) Garmisch Garmisch Darwin Darwin 390 390 390 390 380 380 370 370 370 370 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) CO2 g-b FTS X (ppm) Date CO2 Date 400 400 400 400 (d) (h) Park Falls Park Falls Wollongong Wollongong 390 390 390 390 380 380 380 380 370 370 370 370 360 360 360 360 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) Date CO2 g-b FTS X (ppm) Date CO2 400 400 5 Fig.B1. (i) Lauder Lauder 390 390 Fig. B1. Time series of GOSAT TANSO-FTS SWIR (blue trian- gles) and g-b FTS (pink squares) X and their scatter diagrams CO 380 380 for (a) Bialystok, (b) Orleans, ´ (c) Garmisch, (d) Park Falls, (e) La- 370 370 mont, (f) Tsukuba, (g) Darwin, (h) Wollongong, and (i) Lauder. The 360 360 GOSAT data were retrieved within ±5 degrees latitude/longitude 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 360 370 380 390 400 g-b FTS X (ppm) Date CO2 box centered at each g-b FTS site and the g-b FTS data were the 6 Fig.B2. mean values measured within ±1 h of GOSAT overpass time. Fig. B1. Continued. Acknowledgements. We express our sincere thanks to the mem- 400 Bialyst ok bers of the NIES GOSAT project office, data algorithm team, Orleans atmospheric transport modeling team for their useful comments. Garmisch We thank Nobuyuki Kikuchi in NIES and Komei Yamaguchi in ParkFalls the Japan Weather Association for plotting the data. We would Lamont Tsukuba like to thank anonymous referees and the associated editor for Darw in improving this paper. This work was funded by the Ministry of the W ollongong Environment in Japan. We also thank NASA’s Terrestrial Ecology Lauder Program and the Orbiting Carbon Observatory for their support of TCCON, and acknowledge support from the EU within the projects GEOMON and IMECC. The Lauder TCCON measurements are funded by New Zealand Foundation for Research, Science and 360 370 380 390 400 Technology contracts CO1X0204 and CO1X0406. We thank FT S X CO2 (ppm) the members of RAMCES team at LSCE (Gif-sur-Yvette) for maintaining the FTS at the Trainou station and providing station 3 Fig.B3. Fig. B2. Scatter diagram between GOSAT and g-b FTS X at CO logistics. all FTS sites. The GOSAT data were retrieved within ±5 degrees latitude/longitude box centered at each g-b FTS site and the g-b Edited by: G. Stiller FTS data were the mean values measured within ±1 h of GOSAT overpass time. www.atmos-meas-tech.net/4/1061/2011/ Atmos. Meas. Tech., 4, 1061–1076, 2011 X (ppm) X (ppm) X (ppm) X (ppm) CO2 CO2 CO2 CO2 GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) XCO2(ppm) XCO2(ppm) XCO2(ppm) XCO2(ppm) XCO2(ppm) GOSAT SWIR X CO2 (ppm) GOSAT SWIR X (ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) GOSAT SWIR XCO2(ppm) CO2 1074 I. Morino et al.: Volume mixing ratios of carbon dioxide and methane 1.9 1.9 1.9 1.9 (a) (e) Lamont Lamont Bialystok Bialystok 1.8 1.8 1.8 1.8 1.7 1.7 1.7 1.7 1.6 1.6 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 1.6 1.7 1.8 1.9 g-b FTS X (ppm) g-b FTS X (ppm) CH4 Date CH4 Date 2 2 1.9 1.9 1.9 1.9 (f) (b) Orleans Orleans Tsukuba Tsukuba 1.8 1.8 1.8 1.8 1.7 1.7 1.7 1.7 1.6 1.6 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 1.6 1.7 1.8 1.9 g-b FTS X (ppm) g-b FTS X (ppm) Date CH4 Date CH4 1.9 1.9 1.9 1.9 (g) (c) Garmisch Garmisch Darwin Darwin 1.8 1.8 1.8 1.8 1.7 1.7 1.7 1.7 1.6 1.6 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 1.6 1.7 1.8 1.9 g-b FTS X (ppm) g-b FTS X (ppm) CH4 Date CH4 Date 4 4 1.9 1.9 1.9 1.9 (d) (h) Park Falls Park Falls Wollongong Wollongong 1.8 1.8 1.8 1.8 1.7 1.7 1.7 1.7 1.6 1.6 1.6 1.6 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 1.6 1.7 1.8 1.9 g-b FTS X (ppm) CH4 Date g-b FTS XCH4 (ppm) Date 1.9 1.9 (i) 5 Fig.B4. Lauder Lauder Fig. B3. Time series of GOSAT TANSO-FTS SWIR (blue trian- 1.8 1.8 gles) and g-b FTS (pink squares) X and their scatter diagrams CH ´ 1.7 1.7 for (a) Bialystok, (b) Orleans, (c) Garmisch, (d) Park Falls, (e) La- mont, (f) Tsukuba, (g) Darwin, (h) Wollongong, and (i) Lauder. The 1.6 1.6 GOSAT data were retrieved within ±5 degrees latitude/longitude 2009/1/1 2009/5/27 2009/10/20 2010/3/15 2010/8/8 2011/1/1 1.6 1.7 1.8 1.9 g-b FTS X (ppm) Date CH4 box centered at each g-b FTS site and the g-b FTS data were the 6 Fig.B5. mean values measured within ±1 h of GOSAT overpass time. 21 Fig. B3. Continued. 1.9 Bialyst ok References Orleans Baker, D. F., Law, R. M., Gurney, K. R., Rayner, P., Peylin, Garmisch P., Denning, A. S., Bousquet, P., Bruhwiler, L., Chen, Y. - ParkFalls 1.8 H., Ciais, P., Fung, I. 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