Differences in Algorithms
The MODIS snow mapping algorithm is based on a Normalized Difference Snow Index (NDSI). The NDSI is a measure of the difference between the infrared reflectance of snow in visible and shortwave wavelengths. For Terra data, the algorithm uses MODIS Bands 4 (0.55 µm) and 6 (1.6 µm) to calculate the NDSI. MODIS Band 6 detectors failed on Aqua shortly after launch, so Band 7 (2.1 µm) is used to calculate the NDSI for Aqua. Also with Aqua data, the NDSI/NDVI test for snow in vegetated areas was disabled because the use of Band 7 resulted in too much false snow detection.
The sea ice mapping algorithm did not change from Terra to Aqua