Mesoscale Data Assimilation Experiment in the WWRP B08RDP

A mesoscale data assimilation experiment was performed for the Beijing 2008 Olympics Research and Development Project (B08RDP) under the World Weather Research Program (WWRP) conducted during the period around the Beijing 2008 Olympic Games. In this experiment, the Japan Meteorological Agency (JMA) hydrostatic mesoscale 4D-Var analysis system was modified and utilized to produce accurate initial fields over the China area. In addition to the conventional observations, precipitation data observed by rain-gauges were assimilated as well as data produced from a nowcasting system of the Australian Bureau of Meteorology. The analysis system with rainfall data outperformed other experiments, i.e., the mesoscale analysis without precipitation data and the JMA global analysis, with its quantitative precipitation forecast. This shows that the assimilation of precipitation data can have a positive impact on subsequent model forecasts and that it would be effective even for areas where successive rainfall observations are sparse.