Efforts to Evaluate Shortwave Observations from the CrIS Hyperspectral Infrared Instrument in the NOAA Global Data Assimilation System

Hyperspectral infrared (IR) instruments are capable of providing temperature sounding information through observations in the longwave (LW) and shortwave (SW) parts of the spectrum. In the numerical weather prediction (NWP) community, LW channels have commonly only been assimilated, at least partially owing to challenges inherent in working with SW observations. Despite the ability of SW channels to provide good temperature sounding information that is minimally impacted by trace gases like ozone and water vapor, issues such as solar reflectance and non-local thermodynamic equilibrium (NLTE) effects have hampered the use of these channels in data assimilation (DA). With the advent of smallsats, new interest in using SW observations in DA is emerging as SW instruments are generally smaller, easier, and more cost effective than their LW counterparts to manufacture, launch, and maintain. Efforts have begun at the National Oceanic and Atmospheric Administration’s (NOAA) Center for Satellite Applications and Research (STAR) and the University of Maryland’s Cooperative Institute for Satellite Earth System Studies (CISESS) to systematically evaluate the SW channels from the Cross-track Infrared Sounder (CrIS) in the NOAA Finite-Volume Cubed-Sphere Dynamical Core Global Forecast and Data Assimilation System (FV3 GFS/GDAS). As the first step in these efforts, the existing capabilities to assimilate SW brightness temperatures in the GDAS were evaluated, and areas in need of improvement were identified. In this presentation, the measures taken to improve the GDAS quality control procedures and the specification of observation errors for hyperspectral IR SW CrIS observations will be discussed, and preliminary results of experiments that have been designed to evaluate the performance of the NOAA FV3 GFS/GDAS when assimilating SW CrIS observations in place of LW CrIS observations will be shown. Plans for future work and developments will be also discussed.