Short-term Prediction Research
and Transition Center

Modeling & Data Assimilation Projects

AIRS Profile Assimilation

The SPoRT center seeks to improve short-term weather forecast, especially in the data-sparse region, by the use of satellite-based observations. The Atmospheric InfraRed Sounder (AIRS), aboard the EOS polar-orbiting Aqua satellite, provides near-rawinsonde-quality atmospheric temperature profiles with the ability to resolve some small-scale vertical features. The SPoRT forecast/assimilation system consists of the Weather Research and Forecasting (WRF) model and ARPS Data Assimilation System (ADAS). The forecast domain covers the contiguous United States, western Atlantic Ocean and the Gulf of Mexico. The WRF forecast is initialized with the North American Mesoscale (NAM) analysis and its boundary conditions are update every 3 hours using the NAM forecasts. The forecast/assimilation cycle starts at 00 UTC and runs several hours until the AIRS overpass time is reached (usually around 07-09Z for the morning pass). The WRF forecast is then used as the background field for ADAS to assimilate AIRS data. The forecast continues with ADAS analysis as the new initial state for a total forecast up to 60 hours. The preliminary results indicate that the addition of AIRS profiles improves the temperature and moisture forecasts up to 48 hours. It also has a positive impact on precipitation forecast.

Future work will involve a near real time simulations for an extended period when the most up-to-date Version 5 AIRS profiles become available. This will provide long-term statistics for assessing the impact of AIRS profiles which will be served as a guide to maximize positive AIRS impact.

700 hPa temperature difference between ADAS analysis and background showing the impact of AIRS profiles on ADAS analysis.