Assessing Forest Cover Effects on Passive Microwave Snow Retrievals Using 2009 Snow Observations from NASA's Airborne Earth Science Microwave Imaging Radiometer (AESMIR)

Masking of the microwave signature of snow by forest cover remains one of the most significant impediments to global remote sensing of snow, if for no other reason than the large extent of forest areas. The current AMSR-E snow depth/water equivalent retrieval algorithm includes three elements to help address this masking: compensating terms that are functions of forest cover fraction and forest density, and the use of longer-wavelength 10 GHz observations offering less attenuation and scattering (compared to higher frequencies such as 18 GHz) by the canopy. Airborne observations were collected at both 10 and 18 GHz during flights of NASA’s AESMIR sensor. AESMIR is a passive microwave airborne imager covering microwave bands that are essential for observing key Earth System elements such as snow, sea ice, precipitation, soil moisture, ocean winds, sea surface temperature, vegetation, etc. AESMIR includes these bands in an efficient single mechanical package, and can perform conical and cross-track scans to simulate multiple satellite microwave imagers and sounders. As such, it is an Earth Science facility for post-launch calibration and validation of satellite sensors and as well as for pre-launch algorithm development & new microwave remote sensing discovery. It is well-suited as an inter-satellite calibration tool for constellation missions and long-term climate data records. New results from snow-related flights in January, 2009 will be presented. Imagery at 10 and 18 GHz will be presented from the flights over forested sites in the northeastern US, along with snow ground truth comparisons. The performance of the AMSR-E forest correction will be explored using these frequencies.