A Comparative Study on the Impact of MWHS-2 and MHS Data Assimilation on the Simulation of Rainstorm in the Three Rivers Source Area

Abstract

Based on the mid-scale WRF （Weather Research and Forecasting） numerical model， this study uses the direct assimilation module data from the FY-3C satellite MWHS-2 （Micro-Wave Humidity Sounder 2）， and the WRF-3DVAR （Three Dimensional Variation） method to conduct assimilation comparison experiments on two precipitation processes in the Three Rivers Source area.Moreover， this study extensively compares the effects of two assimilation data sets on simulation results： data from the MWHS-2 （microwave humidity instrument carried by FY-3C） and data from the MHS （Microwave Humidity Sounder） carried by NOAA-18 （National Oceanic and Atmospheric Administration-18）.Results of the study show consistent simulation results for MWHS-2 and MHS data assimilation.For instance， regardless of whether assimilation is conducted or not， the simulated precipitation range is overestimated for precipitations less than 30 mm.However， the simulated range and amount are underestimated for precipitations higher than 30 mm.Furthermore， data assimilation strengthens the 500 hPa southwest wind field， increases the intensity of water vapour transport， shifts the high-altitude trough to the southwest， and strengthens the 300 hPa wind field disturbance， all of which increase the precipitation range above 30 mm and， to a certain extent， improve the precipitation level results.However， compared to the actual situation， the precipitation area is biased southward.Satellite data assimilation significantly improves the range of the water vapour flux field and specific humidity field precipitation areas， but its effects on the intensity improvement are not obvious.At the same time， changes in the water vapour flux field and specific humidity field change the precipitation forecast area and intensity.As for the temperature field， the WRF simulation includes significant errors.Satellite data assimilation shows a certain improvement effect on the temperature field and a more significant improvement effect on the humidity field.In other words， MWHS-2 or MHS satellite data assimilation improves the precipitation forecast in the Three Rivers Source area.These conclusions provide significant guidance for improving the precision of precipitation forecasting in the Three Rivers Source area.

Keywords

• the three rivers source
• torrential rain
• wrf
• assimilation
• mwhs-2
• mhs