陇东南地区短时强降水的雷达回波特征及其降水反演

Analysis on Radar Echo and Precipitation Retrieve of Short-Duration Heavy Precipitation in Southeast Gansu

利用雷达基数据对比分析了天水、庆阳和兰州3部多普勒雷达等距离水平剖面上同步观测的回波强度差异,并研究了陇东南地区短时强降水的雷达回波特征和反演降水。结果表明,当回波强度】10 dBz时,这3部雷达并不存在显著差异;从区域站和自动站的降水量对比分析可知,造成短时强降水的天气学尺度较小,对雷达回波的统计也映证了这一结论。有75%的强降水尺度【20 km,表明原有的气象站并不能较好的反应局地降水;运用分组估测法、整体和分型Z-I关系法定量估测降水,结果发现分型Z-I关系法可以较好的反映陇东南地区的降水特点,较好的解决了低量值高估和高量值低估的问题,其中雨强在15~20 mm·h-1时反演效果最好。

Radar quantitative measurement of precipitation has more advantage in time and space,but the relationship between the change of terrain and precipitation type has great rate.Studying on the radar quantitative measurement of precipitation is one of the main development ways to improve the radar applied ability utilize radar volume scan data.The reflectivity difference of Tianshui,Qingyang and Lanzhou weather radars on the equidistant line were contrasted when they simultaneously observe and the radar echo and precipitation retrieved if occur short-duration heavy rainfall were also analysed by using radar volume scan data.The result shows that:There is no obvious difference when echo more than 10 dBz;Comparing the region station with automatic station of precipitation,comparing the weather scale is less caused by short-duration heavy precipitation than other rainfall type,on the other hand,this conclusion also proved by statistic of radar echo.There are the scale about which 75%of the heavy precipitation are less than 20 km;The original station can't perfectly characterize the local precipitation is demonstrated;The estimated quantitative precipitation through packet of estimation,holistic and categorical Z—I relations were studied.The result shows that:Categorical Z—I relation is better than others on describe precipitation type in the Northeast edge of Tibetan Plateau,thus better solving the problem of underestimated light rain and overestimated heavy rain,and when rainfall belongs to 15-20 mm · h is best.