MMM SEMINAR NCAR
Assimilation of GPS Radio Occultation Observations
in WRF
Using an Ensemble Filter
IMAGe/NCAR
The Ensemble Adjustment Filter in NCAR's Data Assimilation Research Testbed (DART) and the WRF model are used to assimilate GPS radio occultation observations in the troposphere. Ensemble filters implicitly include flow dependent forecast error correlations of moisture with temperature and surface pressure and may be able to produce high-quality assimilations using RO observations. The impacts of model horizontal resolution are investigated by doing assimilations with 50km and 200km WRF models over the CONUS domain for 1-10 January and 18-27 June, 2003. The use of a proper non_local GPS RO observation operator (e.g., excess phase delay, Sokolovsky, Kuo, and Wang, 2005) is also explored with particular emphasis on assimilating GPS observation in the lower troposphere.
Preliminary results show that the DART/WRF assimilations demonstrate positive impacts from the GPS RO refractivity observations for analyses of both moisture and temperature, especially in the lower troposphere. Higher horizontal resolution assimilation systems appear to be needed to obtain positive impacts from GPS RO observations in the lower troposphere. The use of the non_local observation operator with the 50km resolution WRF produces the most positive impacts on the assimilation.
Refreshments 9:45 AM
NCAR-Foothills Laboratory
Bldg 2, Rm1001