多源精细化资料对皖北地区一次雷暴大风的成因分析

Analysis on the Causes of a Thunderstorm in North Anhui Province by Multi-source Refined Data

利用高空、地面、雷达、闪电和ECMWF精细化资料,对皖北地区2016年6月30日的雷暴大风天气进行成因分析。结果表明:(1)这次雷暴大风地点在东北冷涡背景下槽线和副高之间,处于西南气流水汽输送带中急流轴的前左侧。伴有气温陡降、气压涌升、湿度增加和降水的天气现象。(2)大风发生前有较强的不稳定性,中层有显著干层,大风发生后对流不稳定能量迅速减弱,干层也随之消失,大气层结趋向稳定。能量、稳定性都与大风有很好的对应关系。(3)大风发生前中层有深厚干层,当雷暴云外的干冷气流被卷入内部后,在云体前部逐渐下沉,伴随的降水物通过干冷气流的蒸发冷却以及经过融化层下的降水粒子的融化蒸发,气流得到继续冷却,有利于下沉气流的不断发展。(4)大风的发生与风暴移动密切相关,随着风暴的移动,雷暴高压也一同前行。伴随下沉运动而来的快速降温,形成了较强的负浮力效应,以及由于降水的重力拖曳,在雷暴高压的局地辐散和低层冷平流的作用下,促使下沉运动的下降速度加快,并且与大气次级环流圈的下沉支结合,低空风切变明显。这些因素共同导致了地面大风。

The causes of thunderstorm and gale weather in northern Anhui on June 30,2016 were analyzed by using high altitude,ground,radar,lightning and ECMWF fine data.The results show that:(1)The location of the thunderstorm lies between the trough line and the subtropical high in the northeast cold vortex background,and lies on the left and front of the jet axis in the southwest air stream water vapor conveyor belt.Weather phenomena with steep temperature drop,pressure rise,humidity increase and precipitation.(2)There is strong instability before the gale,and there is a significant dry layer in the middle layer.After the gale,the convective instability energy rapidly weakens,the dry layer disappears,and the atmospheric stratification tends to be stable.Both energy and stability have a good correspondence with gale.(3)Before the gale,there is a deep dry layer in the middle layer.When the dry-cold air outside the thunderstorm cloud is involved in the interior,it gradually sinks in the front of the cloud.The precipitation is cooled by the evaporation of the dry-cold air and melted and evaporated by the precipitation particles under the melting layer.The air flow is further cooled,which is conducive to the continuous development of the subsidence air flow.(4)The occurrence of gale is closely related to the movement of the storm.With the movement of the storm,the thunderstorm high also moves forward.The rapid cooling accompanied by the subsidence movement has formed a strong negative buoyancy effect,and the local divergence of thunderstorm high and the effect of low-level cold advection caused by the gravity drag of precipitation accelerated the subsidence movement,and combined with the subsidence branch of the atmospheric secondary circulation,the low-level wind shear is obvious.These factors have led to strong winds on the ground.