CIRA Support to Improving CRTM Brightness Temperatures at 3.9 ìm

The Cooperative Institute for Research in the Atmosphere (CIRA) together with the NOAA/NESDIS/StAR Regional and Mesoscale Meteorology Branch (RAMMB) has extensive experience using the Community Radiative Transfer Model (CRTM). The CIRA/RAMMB synthetic imagery team recently noticed errors in CRTM generated brightness temperatures of approximately 30 K at 3.9 ìm located at the tops of both liquid clouds and ice clouds. This was brought to the attention of the NESDIS/StAR CRTM team who verified that the errors. It was decided that the way reflection of solar radiation by clouds is handled in the CRTM in general needs to be examined. Since the CRTM is part of GSI, the operational data assimilation system, optimal performance of the CRTM is essential for the assimilation of satellite data into operational NWP models.

A direct comparison between synthetic CRTM imagery and observed GOES-13 imagery at 3.9 ìm will be shown. Progress of our JCSDA funded project will also be discussed.