Systematic Evaluation of AIRS Version 6 Thermodynamic Phase, Effective Diameter, and Optical Depth Retrievals

The AIRS version 6 cloud products were released in April, 2013 and are available for all 12 years of the AIRS data record. The version 6 products include retrievals of up to two levels of effective cloud fraction and cloud top pressure for each individual AIRS field of view (the version 5 retrievals were only done on the combined AIRS/AMSU field of regard), and a number of new products including cloud thermodynamic phase. The main role of the thermodynamic phase product is to determine ice cloud scenes for the further retrieval of ice cloud effective diameter, optical thickness, and cloud temperature.

In this work, we will present a thorough and systematic evaluation of the AIRS cloud thermodynamic phase, ice cloud effective diameter, and ice cloud optical thickness retrievals. We will focus on the effects of region, time of year, viewing angle, and effective cloud fraction. (Previous evaluation of the cloud thermodynamic phase algorithm focused on near-nadir scenes only.) This study relies on the space-time gridding approach developed by Smith et al. (2013) to build globally gridded datasets of filtered data. This approach allows us to look at co-relationships between multiple parameters over any time period; robust statistics for even infrequent relationships can be obtained by averaging over the entire AIRS data set.