一次暴雨过程的LAPS分析场与多源观测对比分析

Comparative study on LAPS analysis fields and multi-source observations in a heavy rain event

结合2014年7月初长江流域梅雨期暴雨过程,将融合多普勒雷达基数据、探空和地面观测资料的LAPS分析场,与长江中游暴雨监测外场试验观测基地的多源探测资料进行对比,并对鄂东南暴雨进行初步诊断分析和数值模拟。结果表明,LAPS可降水量、液态水含量和云底高度随时间演变趋势与咸宁微波辐射计观测基本一致。与GFS背景场相比,LAPS风分析更接近风廓线雷达观测;与边界层风廓线雷达观测相比,LAPS分析的风垂直分布高度更接近对流层风廓线雷达观测。LAPS云体高度与云雷达观测相当,可降水量的水平分布及强度均接近GPS/MET反演的整层水汽;降水发展过程中强弱回波分布与SWAN实况分析一致,可刻画出与风云卫星红外云图接近的云区结构。与GFS背景场相比,暴雨中心单站地面各要素随时间分布形势和强度均接近实况观测,可作为地面分析的依据。暴雨区域三维高空形势场与常规探空实况相当,单站基本要素随高度分布较GFS背景场更接近GPS下投式探空观测。对此次鄂东南暴雨初步诊断表明,LAPS可分析暴雨系统的发展演变以及暴雨中心区域有利的中尺度动力配置结构和水汽条件,揭示降水云的发展过程;数值对比试验表明,融合雷达等观测资料后的LAPS系统可为模式提供更优初值,改进暴雨区域降水模拟。

For a rainstorm event of the Meiyu-period in July 2014, LAPS analysis fields are compared with multi-source observation data.Data are obtained by the Mesoscale Heavy Rainfall Observing System(MHROS) over the middle region of the Yangtze River in China. Doppler radar, radiosonde and surface observation data are assimilated by LAPS of the Institute of Heavy Rain(IHR). This heavy rain event is preliminarily analyzed and simulated using LAPS fields. It is shown that the evolution of the integrated total precipitable water, the integrated liquid water and the cloud base of LAPS is consistent with the radiometer observation over Xianning site. Compared to GFS background data LAPS wind analysis is closer to observation of wind profiler radar. The vertical profiler of LAPS wind is closer to that of the troposphere wind profiler radar observation than the boundary layer one. The height of LAPS cloud analysis is close to Ka band cloud radar observation. The horizontal distribution of LAPS integrated total precipitable water is similar to the GPS/MET retrieved water vapor. The distribution of LAPS data-derived radar echo is consistent with the analysis of SWAN during the rainfall event. LAPS can depict the detailed structure of cloud,which is close to the FY-satellite infrared cloud image. Compared to GFS background field the intensity and evolution of LAPS surface analysis fields at the station of rainstorm center are both comparable to surface observation data. The evolution of LAPS analysis fields is close to the conventional radiosonde observation. For the elementary fields of Xianning site, LAPS analysis fields are closer to the GPS sounding data than the GFS background fields. According to the preliminary diagnosis of the heavy rain in the southeast Hubei using LAPS fields, the evolution and the mesoscale dynamic configuration, as well as the favorable moisture conditions of rainstorm center can be analyzed. The development of precipitation cloud can be described. From the results of the numerical experiments, LAPS can provide better initial conditions forWRF model to improve the simulation of heavy rain events.