Research On Data Assimilation And Target Observation Of New Round-trip Flat Float Sounding Data

With the requirements for the accuracy of numerical forecasting are constantly improving and the weather systems of interest are becoming smaller and smaller in spatial scale,the demand for direct observation data,especially sounding data,is also rapidly increasing.The round-trip-flat drift sounding system independently developed by our country can realize the spatio-temporal encryption of sounding observations without increasing additional costs,which effectively alleviated the problem of insufficient and uneven distribution of sounding data,and significantly improved the effectiveness of sounding observation,and a new "Chinese plan" of meteorological sounding has been realized.Therefore,how to effectively apply the round-trip sounding data to numerical weather forecasting to improve the forecasting effect of high-impact weather is extremely important.This paper firstly conducts assimilation research on the data of new sounding ascending and descending sections for a heavy rain process in the Jianghuai region,and then further discusses the application effect of descending section of round-trip sounding system in target observation based on ETKF(Ensemble Transform Kalman Filter)and OSSE(Observation System Simulation Experiments)methods.The main conclusions of this paper are as follows:(1)The quality of the observation data of the new round-trip sounding is relatively reliable.All kinds of observation elements in the ascending and descending sections can meet the standard of operational observation.The second-level sounding products of the system can be effectively assimilated and improve the quality of numerical prediction after the sparse processing of the "specified layer + characteristic layer" scheme.(2)The ascent and descent data of the new round-trip sounding system have a positive contribution to numerical weather prediction.The assimilation of the new sounding data can significantly improve the forecast quality of meteorological elements such as wind field and water vapor field.This makes the lower atmosphere warmer and more humid with enhanced convergence,which is conducive to the accumulation of unstable energy and the triggering of upward motion,thereby improving the forecasting skills of the rainstorm process.(3)The descending section of the round-trip sounding system has a good application prospect in the target observation research.Adding simulated descending data in the highsensitivity area of extreme rainstorms in Henan on "7.20" can improve the forecast quality of multiple physical fields,and can improve the distribution of water vapor and unstable energy in Henan,and more accurately reflect the relationship between precipitation and terrain,which makes the extreme precipitation forecast effect closer to the real.