一次渤海强对流天气系统监测与大风成因探讨

作者：李延江1  景华2  李江波2  常志坤3  张宝贵1

单位：1. 秦皇岛海洋气象台, 河北秦皇岛 066000; 2. 河北省气象台, 河北石家庄 050021; 3. 沧州海洋气象台, 河北沧州 061000

关键词：渤海强对流 中尺度系统监测 东北风分量叠加 可预报性因子

分类号：P458.123

出版年·卷·期（页码）：2013·30·第一期（25-35）

摘要：

利用FY-2E卫星云图、天气雷达、雷电、海上平台、海岛站及海洋模式产品等资料，对2011年9月1日01—06时出现在渤海湾强对流天气成因进行综合分析。结果表明：位于燕山南麓较弱中β尺度云团，在500 hPa西风急流出口处、低层925 hPa切变线及层结不稳定条件下，触发多单体风暴重新发展，造成西岸区短时强降水天气及冰雹天气；中尺度系统主体入海后南压强度少变，在多单体风暴后部下沉气流与后部冷空气动量下传共同作用下，迅速加大渤海湾海区东北大风的分量，在同时具备天文大潮的条件下导致了南岸局部风暴潮灾害的发生。同步监测显示：云图中尺度象元TBB为-25°—-65℃，对流云团强弱交替变化时间为3—6 h，减弱后迅速转向东北岸区；三部天气雷达径向速度图先后监测到NE向低空急流“牛眼”时空尺度特征，同步垂直风廓线（VWP）反演出NE向低空急流由1000 m下降至300 m动量下传过程，与海岛站、平台监测值接近一致，中部与南部海区转为东北大风时间差为3—4 h；20时探空海岸带与风场垂直和水平切变明显，K指数为33℃，SI指数为-3.8℃，对流有效位能Cape为1555 J/kg；海洋中尺度数值产品3—6 h的K指数及海区辐合线的动态模拟与云图TBB中尺度象元、雷达回波移向相对一致，但风速明显偏小10—12 m/s。

Based on TBB data from FY-2E satellite, the weather radar products,, ocean model products, lightning data, meteorological observational data at island stations, and offshore platforms,,the causes of the severe convective weather over the Bohai bay occurred from 01:00 a.m.to 06:00a.m. on 1st September in 2011 have been analyzed synthetically, and the forecasting ability of the numerical products were also tested. The results show that under the unstable conditions of shear line and stratification at 925 hPa, the cloud clusters of β-mesoscale system located at the south of Yanshan Mountains can conduce to redevelopment of the multi-cell storm at the westerly jet stream at 500hPa, and it will cause the severe rainfall and the hail weather within the short term. When the main part of the mesoscale system moves to the ocean, the storm strength have less change.With the interaction of the downdraft behind the multi-cell storm and downward momentum of the cold air behind it, the northeasterly wind component can be increased rapidly over the Bohai sea. The synchronous monitoring show the TBB in the mesoscale pixel is from -25 to -65℃, and the severe-weak transformation time of the convective cloud cluster is 3 — 6 hours from north to south along the west coast of the Bohai Sea. When its intensity weakened, it turns quickly to the northeast coast. The radial velocity diagram in three weather radars have successively detected the temporal and spatial characteristic of low-level jet stream at the northeast direction which is similar to the bovine eye. The momentum descending of the low-level jet stream could be inverted by the vertical wind profile, which is consistent with the data from island meteorological observatory and offshore platforms. When the wind turns to northeastern in central and south sea, there exists a time interval for about 3-4 hours. There is an obvious horizontal and vertical shear through radiosonde data at 20:00 p.m.. The value of K index is 33 ℃, the SI index is -3.8 ℃, and the convection effective potential (CAPE) is 1555 J/kg. The K index from the mesoscale numerical products within 3 and 6 hours and the dynamic simulation of the convergence line over the sea are relatively consistent with the pixel in the mesoscale TBB and the moving direction of the radar echo, but the wind speed is less by 10—12 m·s-1.

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