pier and Polarimetric Weather Radar, sponsored by AMS and organized by the AMS Committee on Mea- surements, will be held on 12-13 January 2002 preced- Radar Images of Venusian Surface ing the 82nd AMS Annual Meeting in Orlando, Florida. This course reviews Doppler weather radar prin- Usin g a new radar system provided by ciples, its application to the observation of weather, NASA, three planetary scientists have obtained and the quantitative measurement of meteorological the first detailed pictures of a large portion of parameters. The goal of this course is to develop an the surface of Venus. An S-band system was understanding of the theory, operation, and applica- installe d at Puerto Rico's tions of meteorological radars. Focus is on meteoro- Arecibo radar observatory under logica l phenomena, their radar signatures, and a $3 million contract from quantitative measurement of weather parameters. Ex- NASA . . . tensive examples of weather phenomena are shown The photograph-like images together with their radar signatures. The latest ad- cover a region of the planet from vances in polarimetric-Doppler weather radar technol- 46° to 75°N and extending 80° og y are presented. The principals of clear air in longitude.. . . Within this re- observation and fair weather phenomena will be dis- gion, the radar picked up two cussed. This course is based on the textbook Doppler major features .. . a large basin, about the size Radar and Weather Observations. of Hudson Bay, and a very bright area about the Who should attend? Meteorologists, weather fore- size of Oklahoma that had been detected previ- casters, physicists, engineers, and other professionals ously and tentatively named Maxwell. The ba- who need to understand applications of Doppler sin is bounded on the north, south, and northwest weather radar. Although there is no specific prereq- by bright rims that seem to be a series of sharp uisite for this course, participants should have an un- ridges several hundred kilometers long. To the derstanding of elementary physics and mathematics. south of the basin, there is a region of greater The following topics will be covered in the course: brightness that resembles the ejecta blankets (re- 1) The principles of weather radar: History of radar gions covered with debris thrown out when large development; electromagnetic waves; polarization; objects, such as meteors, hit the planetary sur- normal and anomalous propagation; pulsed-Doppler face) around some craters of the moon. The pres- radar; signals received from point and distributed scat- ence of ejecta blankets sugests that the Venusian tered; attenuation due to stormy and fair weather; back basin may have been formed by the same type scatter and attenuation cross sections; hydrometeor of events that created the moon's maria. There size distributions; the radar equation; representations may also be two smaller impact craters within of echoes from moving and stationary scatterers; ra- the basin. The bright reflecting area of Maxwell, dar limitations (e.g., range and velocity ambiguities). on the other hand, seems to overlie an older sur- 2) Weather signals: Signal statistics; echo coherency; face and does not have a shape normally con- the weather radar equation; angular and range weight- sidered to be created by the impact of a meteor. ing functions; resolution volume; the reflectivity fac- Instead it seems to be the result of processes tor; correlation of echoes in range and time. 3) Doppler internal to Venus, perhaps indicating a large spectra of weather signals: Discrete Fourier transform eruption of lava. Maxwell's surface appears very and window functions; Doppler spectra of weather rough in the radar pictures and apparently con- echoes; relation between wind, reflectivity, and the tains long parallel ridges extending for hundreds Doppler spectrum; examples of Doppler spectra as- of kilometers. These, like the basin rims, appear sociated with various weather phenomena (e.g., tor- to be the result of tectonic or mountain-build- nadoes). 4) Weather signal processing: Spectral ing activity. No comparable features exist on moments; estimation of reflectivity using range and earth or the moon. time averaging; autocovariance and spectral process- ing to estimate mean Doppler velocity and spectrum width; signal processing for coherent polarimetric ra- Bull. Amer. Meteor. Soc., 57, 1366. dar; performance of the estimators; examples of two- dimensiona l fields of reflectivity factors, radial Bulletin of the American Meteorological Society
Bulletin of the American Meteorological Society – American Meteorological Society
Published: Nov 1, 2001
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