反演同化和直接同化多普勒雷达径向风的对比试验

Contrast Experiments of Doppler Radar Radial Velocity Using Retrieval and Direct Assimilation

针对2003年7月5日江淮流域一次暴雨过程，以NCEP／NCAR1°×1°再分析资料为背景场，采用WRF（weather research and forecasting）模式及其三维变分同化系统，对雷达径向风和E-VAP（extended velocity azimuth processing）反演的水平风场进行了直接同化和反演同化试验，结果表明：直接同化雷达径向风资料后，增加了初始风场的中小尺度信息，改善了垂直速度条件，且在风场作用下水汽分布得到改善；反演同化资料虽然能增加初始场的中小尺度信息，但效果不如直接同化明显；无论直接同化还是反演同化都能改善降水预报，但直接同化好于反演同化，且间隔5～6min比30min的直接同化模拟效果好。

A rainstorm case in the Changjiang-Huaihe River valley on 5th July 2003 is studied in the paper, and the preprocessing and error estimation of radar radial velocity are discussed. Contrast experiments for assimilating grid radial velocity data and E-VAP（ extended velocity azimuth processing ） retrieved data into the nonhydrostatic meso-scale model WRF（ weather research and forecasting） are performed, and results show that the direct assimilation of radial velocity improved the initial wind fields with more meso-scale information and rationalized the distribution of vertical velocity, and also improved the distribution of water vapor through the effect of winds. The assimilation of the retrieved wind data was able to increase the meso-scale information in the initial wind fields, but its effect was not as good as direct assimilation. Precipitation fields analysis shows that the direct and retrieved data assimilation both improved the rainfall forecasts, but as far as assimilation effect on precipitation concerned,the direct assimilation is better than the retrieval assimilation, and the assimilation experiments with 5-6 min assimilation interval are better than those with 30 min interval.