摘要
利用常规气象资料、自动站加密观测资料、卫星云图和雷达资料、NCEP再分析资料、细网格模式资料以及区域中尺度模式,对2017年8月18日夜间沙颍河流域一次短时极端强降水过程的漏报原因和可预报性进行了探讨。结果表明:此次过程发生在西低东高的环流背景下,低层和边界层切变线稳定维持、超低空西南急流建立为强降水过程提供了水汽输送和辐合抬升条件;弱冷空气沿华北南部扩散南下逐渐侵入倒槽,在沙颍河流域形成中尺度辐合线(辐合中心)且长时间维持,触发不稳定能量释放,对暴雨有一定的可预报性。两个中尺度对流云团加强、合并发展为β中尺度对流系统,呈准静止状态,在沙颍河流域下游维持长达6 h是降水增强的直接原因。冷池及其前侧地面中尺度辐合线触发中尺度对流系统,强回波不断在中尺度冷池前侧温度梯度高值带中发展并维持,造成短时极端强降水。本次过程动力条件较弱,水汽主要集中在边界层,热力不稳定条件极为有利,但数值模式对此类对流性暴雨的捕捉能力有限,是暴雨漏报的原因。数值模式和业务预报对降水强度及极端性估计不足,以及预报员缺乏极端天气预报经验,也是造成这次过程预报失误的原因之一。
Using routine meteorological observations,intensive observations from the automatic weather stations,satellite images,radar products,NCEP reanalysis data,fine grid model data and regional mesoscale model data,we have conducted an examination on the reasons for the miss of forecast and the predictability of a short-term extreme precipitation event occurred in the Shaying River Basin at the night on 18 August 2017.The results indicate that this event occurs under the circulation of a high in the west and a low in the east.The stability and continuance of shear lines in the low-level and boundary layer and the establishment of the ultra-low level southwest jet provide the water vapor transport and convergence conditions for the occurrence of severe precipitation.The weak cold air spreads southwards along the south of North China and gradually intrudes into the inverted trough forming a mesoscale convergence line(convergence center)in the Shaying River Basin and maintaining such condition for a long time to trigger the release of unstable energy,which is a good indicator in predicting the occurrence of rainstorm.The two mesoscale convective cloud clusters reinforced and developed jointly into a Meso-β scale Convective System(M_(β)CS)with a quasistatic state.It maintains for 6 hours in the lower reaches of the Shaying River Basin,which is the direct reason that leads to the enhancement of precipitation.The mesoscale convective system is triggered by the cold pool and its front surface mesoscale convergence line,and the strong echo continuously develops and maintains in the high value zone of temperature gradient in front of the cold pool,resulting in short-term extreme precipitation.The weak dynamic condition,the water vapor being mainly concentrated in the boundary layer and the extremely favorable thermal instability condition during this event,as well as the limited capture ability of the numerical model in forecasting this kind of convective rainstorm,all these factors are the causes of the miss of forecast of the rainstorm.The insufficient estimation of numerical models and operational forecasts in the precipitation intensity and its extreme,and the lack of forecasters’experience in forecasting extreme weather,are also some of the reasons for the forecast errors.
作者
胡燕平
单铁良
顾佳佳
HU Yanping;SHAN Tieliang;GU Jiajia(Luohe Meteorological Office of Henan Province,Luohe 462300)
出处
《暴雨灾害》
2021年第5期494-504,共11页
Torrential Rain and Disasters
基金
河南省气象局重点项目(Z201601)
河南省气象局预报员专项(Z201842)
河南省漯河市沙颍河流域创新团队。
关键词
短时极端强降水
低层切变线
对流不稳定
中尺度对流系统
short-term extreme precipitation
low-level shear line
convective instability
mesoscale convective system
