HR: 1330h
AN: C32A-0436    [PDF]
TI: Polar Cloud Studies from the Geoscience Laser Altimeter System
AU: Mahesh, A
EM: ashwin.mahesh@gsfc.nasa.gov
AF: GEST Center, NASA GSFC, Code 912, NASA GSFC, Greenbelt, MD 20771 United States
AU: * Palm, S P
EM: spp@virl.gsfc.nasa.gov
AF: Science Systems and Applications, Inc, Code 912, NASA GSFC, Greenbelt, MD 20771 United States
AU: Spinhirne, J D
EM: jspin@virl.gsfc.nasa.gov
AF: NASA Goddard Space Flight Ctr., Code 912, NASA GSFC, Greenbelt, MD 20771 United States
AU: Gray, M A
EM: gray@climate.gsfc.nasa.gov
AF: L-3 Communications Government Services, Inc., Code 912, NASA GSFC, Greenbelt, MD 20771 United States
AB: The Geoscience Laser Altimeter System (GLAS), launched on board the Ice, Cloud and Land Elevation Satellite in January 2003 provides space-borne laser observations of atmospheric layers. In the polar regions, satellite observations of clouds and snow surfaces appear similar at both infrared and visible wavelengths. The GLAS laser profiling permits unambiguous detection of clouds over snow and ice surfaces, and allows accurate climatologies of clouds in the high latitudes to be compiled. These observations also allow the analysis of the validity of passive observations of polar cloud retrievals for the first time. Data from the Moderate Resolution Imaging Spectrometer aboard the Aqua satellite is examined along with GLAS observations of cloud layers. In more than three-quarters of the cases, MODIS scene identification from spectral radiances agrees with GLAS. These studies illustrate the capabilities of active remote sensing to validate and assess passive measurements, and also to complement them in studies of atmospheric layers. Polar clouds are also an important factor for the accuracy of the altitude measurements of ice sheet elevation change. Multiple scattering through even the thinest clouds introduces an effective pulse spreading and altitude bias. Pulse spreading up to 10 of meters is observed in data. The GLAS mission was designed so that cloud clearing and corrections would permit centimeter accuracies for surface elevation change. The adequacy the cloud detection and clearing for surface measurements is under analysis and initial results are presented.
DE: 0399 General or miscellaneous
DE: 1610 Atmosphere (0315, 0325)
DE: 3309 Climatology (1620)
DE: 3349 Polar meteorology
DE: 3360 Remote sensing
SC: Cryosphere [C]
MN: 2003 Fall Meeting