川东平行岭谷对四川盆地暴雨影响的数值试验

Numerical Experiment on the Influence of Parallel Ridge Valley in East Sichuan on Rainstorm in Sichuan Basin

利用地面自动站观测和NCEP/NCAR再分析资料,对2014年8月8~9日四川盆地区域暴雨过程进行分析,利用WRFV4.0模式开展了数值模拟研究,在模拟结果和实况较为吻合的情况下,通过地形敏感性试验,分析了川东平行岭谷对暴雨落区和强度的影响。研究表明:本次暴雨过程发生在西太平洋副热带高压被热带气旋切断的形势背景下,由高空槽稳定维持所造成,WRF模式控制试验能够较好的重现此次暴雨过程。川东平行岭谷对降水的落区和强度有较大影响,升高的川东平行岭谷使盆地中部到北部的雨带西移,使盆地西部降水量增加、北部降水量减少。进一步研究表明,升高后的川东平行岭谷通过地形辐合和强迫抬升改变四川盆地700hPa环流形势及850hPa的水汽辐合分布,从而影响四川盆地降水落区和强度,其对850hPa环流形势的影响较小。

Based on the observation of the automatic ground stations and NCEP/NCAR reanalysis data,the regional heavy rain in Sichuan basin from August 8 to 92014 was analyzed,and the rainstorm process was simulated by WRF V4.0 numerical model.In the case that the simulation results are in good agreement with the actual situation,the influence of parallel ridge valley in east Sichuan on the rainstorm area and intensity is analyzed by the terrain sensitivity tests.The study shows that the rainstorm is caused by the stable maintenance of the high trough in the background of the subtropical high in the western Pacific cut off by the tropical cyclone.The control test of WRF V4.0 model can reproduce the rainstorm process well.The parallel ridge valley in east Sichuan has a great influence on the area and intensity of precipitation.The elevated parallel ridge valley in east Sichuan makes the rain belts in the central to northern parts of the basin move westward,and the precipitation in the western part of the basin increases,while that in the northern part of the basin decreases.Further study shows that the elevated parallel ridge valley in east Sichuan changes the 700 hPa circulation situation and 850 hPa water vapor convergence distribution in Sichuan basin through topographic convergence and forced uplift,which affects the precipitation area and intensity,and has less influence on the 850 hPa circulation situation.