一次盆地强降雨过程的多模式结果对比分析

A Comparative Case Study of an Extreme Rainstorm over Sichuan Basin Using Various Models

运用西南区域数值模式SWCWARMS、欧洲中心细网格预报模式EC以及国家气象中心中尺度区域模式GRAPES对2018年6月25日12时~26日12时发生在四川盆地内的一次强降雨过程进行预报对比分析,多模式结果表明:EC模式与GRAPES模式对盆地西北部的暴雨漏报现象较为突出,SWCWARMS模式能较好模拟整个雨带的强度与位置,对比中尺度系统西南涡的模拟,在低涡出现和发展的12小时内,EC模式对低涡的预报能力偏弱,预报降雨量偏小,低涡位置与强度预报GRAPES与实况最接近,SWCWARMS模式与GRAPES相似,但仅有SWCWARMS预报出低涡南侧与低涡西北象限的强降雨,在低涡减弱阶段,3种模式趋于相同。EC与GRAPES模式在四川盆地内的初始涡度偏弱,辐合偏小,盆地西部边坡对流层低层垂直上升运动偏小,相对湿度偏低,这导致了EC和GRAPES模式在四川盆地西部边坡降雨强度偏小,仅有SWCWARMS模式与实况最符合,尤其对复杂地形下的降雨过程有较强的预报能力。

A comparative study of a rainstorm over the Sichuan Basin during 12 UTC 25 June to 12 UTC 26 June 2018 is done by using the regional model of Southwest China(SWCWARMS),fine grid forecast model of European Center(EC)and regional model of China Meteorological Center(GRAPES).The various models’results show the missing alarm rate of EC model and GRPAES model is higher than SWCWARMS model.The precipitation amount and precipitation center position in SWCWARMS are close to actual situation.For the simulation of meso-scale synoptic system-Southwest China vortex(SWCV),during the process of its occurrence and enhancement in the initial 12 hours,EC cannot predict SWCV well and the rainfall prediction is much less than actual precipitation.GRAPES predicts the evolution of SWCV’s position and intensity accurately.Its result is most close to FNL data and SWCWARMS’s result is similar to the GRAPES’s.However,only SWCWARMS can give the heavy precipitation located at the south side and northwest quadrant of SWCV.At the fading stage of SWCV,the three models tend to be the same.At the aspect of orographic precipitation,GRAPES model is the worst model for the 6-hour accumulated simulation and SWCWARMS performs best.Meanwhile,EC model is the medium one.In the Sichuan Basin,the vorticity and convergence in EC and GRAPES are smaller than SWCWARMS.At the west edge of Sichuan Basin,the vertical velocity and relative humidity at low-level troposphere in EC and GRAPES is smaller than SWCWRAMS as well.All above lead to the lighter precipitation at the west edge of Sichuan Basin.Only the simulation precipitation from SWCWARMS model comes up to the real rainfall situation.Especially it has good ability to simulate the rainfall over complex terrain and better prediction.