| Meteorological satellite observation data can provide global high spatial and temporal resolution atmospheric observation information,and its assimilation application has been widely recognized for improving the accuracy of numerical weather prediction.With the launching of domestic meteorological satellites and the improvement of data quality,improving the operational prediction level by making full use of the meteorological satellite data that is independently developed in China will play a good role in promoting the development of numerical simulation in China.In the main area of human activities-land surface,the assimilation of Chinese satellite data is of great scientific and practical significance.due to the influence of complex surface,the application of satellite data assimilation in the land surface area is more complicated than the sea surface.It is the key and difficult point in the current satellite data assimilation research.Therefore,In order to study the possibility of applying satellite data over land to operational forecasting,The characteristics of the southwest vortexes are analyzed by using the 700 hPa and 850 hPa synoptic maps at 8am and 8pm(Beijing time)provided by the China Meteorological Administration(CMA)and the daily four times ERA-Interim reanalysis data with 0.75°×0.75°spatial resolution provided by the European Centre for Medium-Range Weather Forecasts(The European Centre for Medium-Range Weather Forecasts).The generated numbers,moving paths,life periods and precipiting impacts are analyzed based on the 149 southwest vortexes that generated from June to August between 2010 and 2017.On this basis,the cyclic data assimilation test and single-time data assimilation test with dynamic surface emissivity and the atlas emissivity were designed to study two Southwest Vortex Rainstorm Processes with WRF model three-dimensional variational system and FY-3C MWHS-2 data.The results show that:(1)the Southwest vortexes mainly occurred in June and the vortexes impacted by typhoons are mostly generated in August.furthermore,the eastward moving type counts the most while the southeastward moving type occurs the least.(2)The precipitation produced by the southwest vortex mainly are heavy rain,hard rain,and downpour.Compared with August,southwest vortex is more likely to cause heavy rainstorm disasters in June or July.(3)The number of pixels entering the assimilation system of dynamic surface emissivity assimilation test is larger than that of atlas emissivity assimilation test,and the difference of emissivity value between the two tests is small.(4)The assimilation test has improved the initial field information in the middle and upper levels,while the improvement in the lower layer is smaller.At the same time,it is found that there is a case-dependency between the atlas emissivity test and the dynamic surface emissivity test,and the improvement effects of the two tests on different initial fields are different.(5)In prediction field,cyclic assimilation can greatly improve the prediction of temperature,wind and relative humidity in the middle and upper levels.Improving Rainfall area and precipitation forcast accuracy,and weaking the phenomenon of omission and false report,so that the scope of rain area and the size of rainfall are closer to the reality.Generally speaking,assimilating MWHS-2 data can improve precipitation forecast to a certain extent.In addition,the cyclic assimilation scheme can effectively improve the 48-hour precipitation forecast by making full use of satellite data,and the forecast effect is better than that of single-time assimilation test. |
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