Extending the Global and Regional Cloud Amount trends from MODIS through VIIRS
Abstract:Monitoring Earth from satellite observations by retrieving geophysical variables, such as cloud amount, requires continuity between satellite missions. The continuity also requires careful calibration and instrument characterization. The MODIS VIIRS Cloud Mask is an approach to ensure continuity in cloud cover from MODIS through the VIIRS era by using similar spectral observations and the same algorithm. This presentation discusses the algorithm approach, compares results from the two instruments and discusses validation through comparison with the CALIOP lidar.
The MVCM philosophy is the same as for MODIS cloud mask (MOD35) and ingests similar L1b bands for VIIRS and MODIS processing. The MVCM contains similar output as MODIS (48 bits/pixel) MVCM output contains confidence of clear sky (Q) values. The algorithm is the same for MODIS and VIIRS instrument and the ancillary data similar.
Agreement between CALIOP and MVCM Aqua, and between CALIOP and MVCM NPP is reasonable and approaches that between CALIOP and MYD35 (Aqua MODIS cloud mask). Agreement between MVCM Aqua and MVCM NPP is also reasonable. Dependences on view angle and field-of-view differences between MODIS and VIIRS are presented and discussed. The VIIRS has a constant field-of-view with viewing angle, differing from MODIS and resulting in differences in cloud amount.