C44A-07
Impact of Cloud and Blowing Snow on Ice Sheet Altimetry: a Comparison between ICESat and ICESat-2
Thursday, 17 December 2015: 17:30
3007 (Moscone West)
Yuekui Yang, Universities Space Research Association Columbia, Columbia, MD, United States, Alexander Marshak, NASA Goddard Space Flight Center, Greenbelt, MD, United States, Stephen P Palm, Science Systems and Applications, Inc., NASA Goddard Space Flight Center, Lanham, MD, United States and Tamas Varnai, University of Maryland Baltimore County, JCET, Baltimore, MD, United States
Abstract:
Clouds and blowing snow have long been a concern for lidar altimetry. Scattering inside the layer increases the photon path and makes the surface appear further away from the satellite. This effect is referred to as “atmospheric path delay”. The ICESat and ICESat-2 missions’ high accuracy requirement on the ice/snow surface elevation measurements makes understanding and quantifying this effect essential. We have developed a comprehensive framework that can simulate the analog waveform behavior of the Geoscience Laser Altimeter System (GLAS) onboard ICESat and the photon counting signal of the Advanced Topographic Laser Altimeter System (ATLAS) onboard ICESat-2. In this presentation, we will (1) review the cloud and blowing snow distributions over the polar ice sheets; (2) discuss how different factors affect the value of the atmospheric path delay, such as scattering layer height, optical thickness, and lidar field of view (FOV); (3) demonstrate that the delay is much less for ICESat-2 (centimeter level) compared to ICESat (decimeter level) due to the much smaller lidar FOV; (4) show the cloud detectability difference between ICESat and ICESat-2 and its implication to path delay corrections. The effect of cloud and blowing snow on first photon bias will also be discussed.
