GSI 4D EnVar for Regional Applications


The DTC tested and evaluated 4D EnVar capabilities for regional mesoscale scale applications. This work started with an examination of current available capabilities of running ensemble-based DA using the Advanced Research Weather Research and Forecast (WRF) (ARW) forecast system. The DTC evaluated the performance of ensemble-based GSI and impacts of running such a system on regional forecasts, against GSI hybrid using global ensemble as in the current operational regional systems at the National Oceanic and Atmospheric Administration (NOAA) for its Rapid Refresh (RAP) system. The results show a great potential of using 4D EnVar to improve mesoscale analyses and forecasts. However, a few working areas were also identified for further improvement of this GSI capability. The DTC fixed some GSI code bug based on the findings and also suggests an overall examination of the GSI code and configurations for an optimal performance.