雷达反演资料的Nudging同化对华南暴雨过程短临预报的影响

Nudging Radar Data Impact on Southern China Rainstorm Short-term Forecast

基于1 km分辨率的华南区域短临预报模式,利用松弛逼近法Nudging同化由雷达观测反演的风场和水物质,选取两次华南前汛期降水过程进行试验,目的在于研究调整初始风场和调整初始水物质场对于短临模式降水预报的不同影响。首先对反演结果进行了初步验证,结果表明试验中反演结果是基本合理的。进而将雷达反演结果 Nudging同化到模式预报中,和控制试验(test-ctl)进行比较可以看出:(1)仅Nudging同化水物质试验(test-qcqr)可以比较有效地改进0~7 h降水预报,特别是对于0~2 h降水偏少的现象改进最为显著。(2)仅Nudging同化风场试验(test-uv)对3~7 h预报有一定的改进,但总体来说改进的幅度很小。(3)同时Nudging同化水物质及风场试验(test-qcqr-uv)的结果最优,它对于0~10 h降水预报都有比较明显的改进。从微物理量的垂直分布来看,前期模式降水主要来源于Nudging同化到初始场中的水物质信息,所以test-qcqr和test-qcqr-uv对前期降水预报的改进都比较明显。Nudging同化雷达反演风场资料可以迅速的调整初始场中低层辐合线存在的偏差,但是它对降水的影响必须配合水物质的调整才能比较明显地体现出来。总的来说,Nudging同化水物质对于短临降水预报影响最为显著,而在此基础上Nudging同化雷达风场对于3 h之后的降水预报会有更好的改进。

Based on one kilometer resolution short-term forecast model in Southern China,we adopt the Nudging method to assimilate wind and water substances from radar retrieve. Two typical rainfall cases of pre-flood season in Southern China are conducted in order to study different influence on precipitation forecast of short-term forecast model after improving wind and water substances at initial moment. The results show that the retrieve method is reasonable basically. And then Nudging radar retrieve results to forecast model and compare with control test( Testctl). The results show that:( 1) The test of only Nudging water substances( Test-qcqr) can improve precipitation forecast during 0 ~ 7 h,especially for making rainfall which is less than normal data at 0 ~ 2 h better.( 2) The test of only Nudging wind( Test-uv) makes better on 3 ~ 7 h forecast,but the improvement rate is generally small.( 3)The test of both Nudging radar retrieve wind and water substances( Test-qcqr-uv) is best. It has significant improvement on 0 ~ 10 h precipitation forecast. From the vertical distribution of micro-physical point,we obtain that the main source of precipitation in the early stage is from water substances,so both test-qcqr and test-qcqr-uv are better obviously for pre-rainfall forecast. Nudging radar retrieve wind can quickly regulate bias of convergence lines at the lower level,but it must be with water substances. In general,Nudging water substances is most significant on short-term forecast,while Nudging radar retrieve wind can make better improvement on precipitation forecast after 3 hours on the base of the former.