The Study On Four-Dimensional Variational Data Assimilation Technique Of FY-2 Satellite Wind

Atmospheric motion vectors data plays a very important role in improving the forecast effect of weather systems such as the heavy rain and typhoon and in improving the analytical field quality and mid-term forecast ability of global numerical weather prediction system.However,due to the large data errors and the imperfect quality control scheme in satellite data assimilation,the utilization of satellite data is very low.Moreover,the current YH4 DVAR system does not assimilate FY-2 atmospheric motion vectors data.Therefore,how to assimilate the FY-2 atmospheric motion vectors data efficiently by studying and designing a series of new functional modules based on the existing global4-D variational assimilation framework is an urgent problem to be solved.Based on the existing four-dimensional variational assimilation system of global meteorological data,this paper,aiming at the shortcomings and deficiencies of the current satellite data assimilation methods,studies the highly efficient global 4-D variational assimilation technique of FY-2 atmospheric motion vectors data,and solves the atmospheric motion vectors data assimilation preprocessing of FY-2,the data channel section,the quality control,the analysis of the errors characteristics,the design of the observation operator and other key issues,and achieves the FY-2 atmospheric motion vectors data in YH4 DVAR.Finally,the effect of FY-2 atmospheric motion vectors data on the global mid-term numerical weather prediction was tested by assimilation and forecast experiment.Through research and experiment,the main conclusions are follows:(1)By comparing FY-2G AMVs with NCEP FNL global atmospheric analysis field data,the quality of FY-2G AMVs was evaluated.The results show that the AMVs of infrared and water vapor channels all meet the unbiased Gaussian distribution,so no bias correction is needed in the data assimilation process of FY-2 satellite.The errors of AMVs of water vapor channel is smaller and the quality is higher.The satellite wind speed of FY-2G satellite is obviously better than that of the wind direction.According to the analysis results of latitude and longitude wind,the errors of AMVs in the equatorial region is the smallest.From the analysis of wind direction and wind speed,the errors of wind speed in the equatorial area is the smallest,but the wind direction errors is the highest in this area.The errors of AMVs in all regions vary greatly with the fluctuation range of altitude.The height of FY-2G AMVs exist systematically low problem.(2)Assimilation of FY-2E and FY-2G AMVs can both have an impact on the geopotential height field,temperature field and wind field of the initial field and the forecast field of the weather prediction.Among them,the influence on the temperature field forecast is neutral,while it has a positive effect on the geopotential height field and the wind field prediction,especially the improvement on the wind field.