Assessment of the Assimilation of AMSU-A and IASI Radiance Data with GSI-Based 3D-var Data Assimilation System in WRF-ARW Model over UAE

The impact of direct Data Assimilation (DA) of brightness temperatures from the Advanced Microwave Sounding Unit - A (AMSU-A) and Infrared Atmospheric Sounding Interferometer (IASI ) over the UAE, using the Community Radiative Transfer Model (CRTM) embedded in GSI system was evaluated using the Advanced Research WRF-v 3.8.1 (WRF ARW) model from the national Center for Atmospheric Research (NCAR).

In this study, we have performed a control simulation and 3 Data Assimilation simulation with microwave, AMSU-A data (AMSU), infrared, IASI data (IASI) and, combination of AMSU and IASI data which interested days with precipitation and fog events.

The impacts of DA on temperature and moisture forecasts up to 24 hours at the surface and profile have been investigated in five major airport locations over UAE: Abu Dhabi, Dubai, Sharjah, Alain and, Al Maktum airports. Results from the WRF runs showed that the forecasts were in better agreement with ground observations when assimilation performed using AMSU-A radiance data. Compared to the control simulation, the Mean Absolute Error (MAE) for AMSU-A assimilated simulation was lower than 28%, 19 % and 28% for temperature, relative humidity and dew-point temperature, respectively. Whereas, Root Mean Square Error (RME) was lower than 27%, 19%, and 25% respectively. The WRF profiles obtained from AMSU-A DA showed good agreement with Radiosonde data in the lower and middle layers at the Abu Dhabi airport when compared to profiles obtained from control simulations. Additionally, estimation of precipitations obtained from assimilation of AMSU-A and IASI into WRF showed significant improvement compared to control run