Comparison of polar cloud cover statistics between MODIS, AVHRR Pathfinder, and GLAS

Gross cloud statistics are compared between the MODIS (Moderate Resolution Imaging Spectroradiometer), AVHRR (Advanced Very High Resolution Radiometer) Polar Pathfinder, and GLAS (Geoscience Laser Altimeter System) products. Cloud amounts derived from these three instruments will be contrasted for day, night, and terminator conditions of solar illumination. Daily averages over a relatively short time period (October and November, 2003) are compared between MODIS and GLAS. No attempt is made to collocate the two, but because each instrument views polar regions 14 times per day, it is reasonable to compare daily and monthly means. Though limited by sampling differences, comparisons are also possible between GLAS cloud heights and success rates of various MODIS cloud tests to evaluate the efficiency of MODIS spectral cloud detection tests (e.g., cirrus tests, low cloud tests, etc.). Longer term comparisons are made between MODIS and AVHRR Pathfinder data. Monthly means are contrasted for spring 2000 through summer 2002 in order to determine similarities and/or discrepancies between the two in the yearly cycle of cloudiness near each pole.