Status and Progress in All-sky Assimilation of Cloud-Affected Hyperspectral Infrared Radiances in GEOS


Wei Gu*, Yanqiu** and Yingtao Ma***

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

The majority of hyperspectral infrared radiance observations in typical low or mid-tropospheric channels
have been excluded from the assimilation due to their cloud-affetced nature. 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 impacted by clouds
and precipitation in most data assimilation systems, including GEOS. Recently, the Global Modeling and
Assimilation Office(GMAO) has initiated efforts with the goal of asimilating cloud-affected hyperspectral
infrared radiances.

The initial focus has been directed towards CrIS-FSR observations from water-vapor channels that are
rejected by cloud detection but exhibit sensitivity exclusively to mid- and upper-tropospheric cloud.
The capability of the GEOS model and CRTM in simulating infrared radiances affected by clouds has been
evaluated. The all-sky Jacobians with respect to temperature and specific humidity have been compared
to their corresponding clear-sky counterparts to assess the impact of cloud presences on these Jacobians.
The Jacobians with respect to the hydrometeors such as cloud liquid water, cloud ice, rain and snow have
also been examined to observe their behaviors under varying cloud conditions. These hydrometeors are
control variables adopted in the all-sky assimilation not only for infrared radiances but also for
microwave radiances from GMI, MHS and AMSR2 in GEOS. Symmetric cloud effects have been investigated to
assess their robustness when treated as the cloud proxy in observation error modeling that incorporates
the inter-channel correlations and situation dependency on symmetric cloud effects.

The effective radius for all hydrometeors will be sourced from the GEOS model. The bias correction and
quality control(QC) processes will be adapted to accoommodate the modifications necessary for all-sky
assimilation before conducting comprehensive 4dEnVar experiments to assess the impacts on the analysis
and the forecast performance of GEOS.