超级单体引发的一次大风风速估算及其机理探讨

基于地面、高空、雷达探测资料和GFS再分析资料,对一次超级单体引发的大风风速进行估测,并探讨大风的形成机理。研究表明:①伴随着大风天气的发生,地面气温快速下降、比湿减少;大风的发生与风暴单体的发展程度和中气旋强弱在时间上具有一致性,风向分布与中气旋的旋转方向相同;大风地点发生在大尺度背景下垂直速度下沉区域。②风速具有随着不同等级径向速度面积增加而增加的现象,用其可以大致估算风力等级。③多单体的合并使得风暴单体变强,成为超级单体风暴;通过动量下传,促使空中大风快速下沉至近地层辐散,使之成为地面大风的形成机制之一。④由于中等雨量的拖曳作用,将中层大气拖曳至近地层;地面气温显著降低,表示环境负浮力的增大,加强了中层大气的下沉运动。⑤风暴合并、动量下传、降水拖曳和环境负浮力增加以及风暴后部下沉气流等共同作用引起了地面大风。

Estimation on Gale Speed Caused by One Supercell and Study for Mechanism

Based on ground, upper air, radar detection and GFS reanalysis data, aone gale speed was estimated, and its mechanism was studied. The results were as followings. With the occurrence of gale weather, the ground temperature was rapidly declining and the specific humidity was reduced. The occurrence of the gale was consistent with the development of the storms and the strength of the mesoscale in time, and the wind direction was the same as the direction of rotation of the mesoscale. The gale occurred in areas where vertical velocity sank under large-scale background. The wind speed increased with the radial velocity area of different grades, which could be used to estimate the wind level. The combination of multiple storms made the storms stronger, becoming a supercell storm. Propagating downward through the momentum promoted the upper air sank to the level near ground rapidly, and it was the formation mechanism of ground wind. The moderate rainfall dragged the middle of the storm to near the stratum. That the ground temperature was significantly reduced indicated the increase of environmental negative buoyancy, to strengthen the middle of the atmosphere sinking movement. Storm merging, momentum downward, precipitation delay and the increase of environmental negative buoyancy, and sinking airflow bear storm caused the ground gale.