High Albedos of Cirrus in the Tropical Pacific Warm Pool: Microphysical Interpretations from CEPEX and from Kwajalein, Marshall Islands

High Albedos of Cirrus in the Tropical Pacific Warm Pool: Microphysical Interpretations from... AbstractRecent studies suggest that extensive shields of cirrus clouds over the equatorial Pacific warm pool may have a significant influence on the global climate, yet details of the links between cloud microphysical properties, upper-tropospheric latent and radiative heating rates, and climate are poorly understood. This study addresses whether relatively reflective ice crystals with dimensions smaller than about 100 m near the tops of tropical cirrus clouds, produced by deep convection when the sea surface temperature exceeds 300 K, are principally responsible for the high albedos observed in this region.In situ measurements of ice crystal size distributions and shapes, acquired during the Central Equatorial Pacific Experiment (CEPEX), are used to derive cloud ice water content (IWC), particle cross-sectional area (A), and other microphysical and optical properties from particles with sizes down to 5 m. These measurements are needed to ascertain the microphysical properties primarily responsible for determining cloud optical depth and albedo in visible wavelengths and were acquired by a Learjet flying in tropical cirrus and occasionally in convection between altitudes of 8 and 14 km (20C to 70C). Previously unanalyzed microphysical measurements in the vicinity of Kwajalein, Marshall Islands, acquired in the mid-1970s from a WB57F aircraft between altitudes of 5 and 17 km, are also used to study the variation in microphysical properties from cirrus base to top, using a combination of constant-altitude penetrations and steep ascents and descents through cloud.Analysis shows that IWC, A, and various measures of particle size all tend to decrease with decreasing temperature and increasing altitude, although considerable scatter is observed. Small ice crystals make up more than half the mass and cause more than half the extinction on average in the upper, colder parts of the cirrus; however, the predominantly large particles in the lower, warmer parts of the cirrus contain at least an order of magnitude greater mass and are dominant in producing the high observed albedos. An examination of the lidar and radiometer data acquired onboard the NASA ER-2, which overflew the Learjet during CEPEX, supports the conclusion that the higher, colder regions of the cirrus typically have volume extinction coefficients that are only about 10 of those in the lower, warmer regions. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of the Atmospheric Sciences American Meteorological Society

High Albedos of Cirrus in the Tropical Pacific Warm Pool: Microphysical Interpretations from CEPEX and from Kwajalein, Marshall Islands

Loading next page...
 
/lp/ams/high-albedos-of-cirrus-in-the-tropical-pacific-warm-pool-microphysical-cmN8RXSVjR
Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0469
D.O.I.
10.1175/1520-0469(1996)053<2424:HAOCIT>2.0.CO;2
Publisher site
See Article on Publisher Site

Abstract

AbstractRecent studies suggest that extensive shields of cirrus clouds over the equatorial Pacific warm pool may have a significant influence on the global climate, yet details of the links between cloud microphysical properties, upper-tropospheric latent and radiative heating rates, and climate are poorly understood. This study addresses whether relatively reflective ice crystals with dimensions smaller than about 100 m near the tops of tropical cirrus clouds, produced by deep convection when the sea surface temperature exceeds 300 K, are principally responsible for the high albedos observed in this region.In situ measurements of ice crystal size distributions and shapes, acquired during the Central Equatorial Pacific Experiment (CEPEX), are used to derive cloud ice water content (IWC), particle cross-sectional area (A), and other microphysical and optical properties from particles with sizes down to 5 m. These measurements are needed to ascertain the microphysical properties primarily responsible for determining cloud optical depth and albedo in visible wavelengths and were acquired by a Learjet flying in tropical cirrus and occasionally in convection between altitudes of 8 and 14 km (20C to 70C). Previously unanalyzed microphysical measurements in the vicinity of Kwajalein, Marshall Islands, acquired in the mid-1970s from a WB57F aircraft between altitudes of 5 and 17 km, are also used to study the variation in microphysical properties from cirrus base to top, using a combination of constant-altitude penetrations and steep ascents and descents through cloud.Analysis shows that IWC, A, and various measures of particle size all tend to decrease with decreasing temperature and increasing altitude, although considerable scatter is observed. Small ice crystals make up more than half the mass and cause more than half the extinction on average in the upper, colder parts of the cirrus; however, the predominantly large particles in the lower, warmer parts of the cirrus contain at least an order of magnitude greater mass and are dominant in producing the high observed albedos. An examination of the lidar and radiometer data acquired onboard the NASA ER-2, which overflew the Learjet during CEPEX, supports the conclusion that the higher, colder regions of the cirrus typically have volume extinction coefficients that are only about 10 of those in the lower, warmer regions.

Journal

Journal of the Atmospheric SciencesAmerican Meteorological Society

Published: Sep 12, 1996

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off