Status and Progress in the all-sky Hyperspectral Infrared Radiance Assimilation in GEOS


Wei Gu, Yanqiu, Yingtao Ma*, Oreste Reale, Erica McGraph-Spangler, Niama Boukachaba, Manisha Ganeshan

GMAO @ NASA/GSFC
* CIRA @ NOAA/NESDIS/STAR

The majority of hyperspectral infrared radiance observations peaking in the lower and mid-troposphere have been excluded from the operational GEOS data assimilation system by cloud detection scheme. The significance and challenges of assimilating these cloud-affected observations have attracted the attention of the research community, as substantial progress has been achieved in utilizing microwave radiances affected by clouds and precipitation in many data assimilation systems, including GEOS. While the Global Modeling and Assimilation Office(GMAO) has made significant progress on cloud-clearing infrared research, this parallel study marks the first effort to assimilate directly cloud-affected hyperspectral infrared radiances in the GEOS.

This initial study is focused on CrIS-FSR water-vapor channels. The capability of the GEOS model and CRTM in simulating infrared radiances affected by clouds has been evaluated, and the all-sky brightness temperature Jacobians with respect to temperature, specific humidity, and hydrometeors are examined closely in varying cloud conditions. With hydrometeor control variables in the GEOS, several important aspects of all-sky IR radiance assimilation are investigated. Symmetric cloud effects  are assessed for their robustness when used as the cloud proxy in observation error modeling that incorporates the inter-channel correlations and situation dependency on symmetric cloud effects. The effective radius, bias correction and quality control processes will also be adapted to accommodate modifications necessary for all-sky infrared assimilation before comprehensive 4dEnVar experiments are conducted to assess their impacts on the analysis and forecast performance of GEOS.