2018年1月北大西洋上一个具有“T”型锋面结构的超强爆发性气旋的分析

Analysis of a super explosive cyclone with frontal "T-bone" structure over the Northern Atlantic in January 2018

中文关键词:  爆发性气旋  “T”型锋面结构  锋生函数  WRF模式  Zwack-Okossi方程

英文关键词:Explosive cyclone  Frontal "T-bone" structure  Frontogenesis function  WRF model  Zwack-Okossi equation

中文摘要:

      利用欧洲中期天气预报中心（ECMWF）提供的0.5°×0.5° ERA-Interim再分析资料，麦迪逊-威斯康星大学气象卫星研究所（CIMSS）提供的地球静止环境业务卫星（GOES-EAST）红外卫星云图和天气预报模式（WRF）的模拟结果，对2018年1月3—6日发生在北大西洋上的一个具有“T”型（T-bone）锋面结构的超强爆发性气旋进行分析。该爆发性气旋在较暖的湾流上空生成，沿海表面温度大值区向东北方向快速移动，生成后6 h内爆发性发展，24 h中心气压降低48.7 hPa。高空槽加深、涡度平流加强和低层较强的大气斜压性为气旋快速发展提供了有利的环流背景场。由于气旋发展迅速，低层相对涡度急剧增大，低压中心南部来自西北方向的干冷空气随气旋式环流快速向东推进，与东南暖湿气流汇合，锋生作用较强。较暖的洋面对西北冷空气的加热作用使得交汇的冷、暖空气温度梯度较小。减弱东移的冷锋与暖锋逐渐形成近似垂直的“T”型结构。用Zwack-Okossi方程诊断分析表明，非绝热加热、温度平流和正涡度平流是该爆发性气旋发展的主要影响因子。气旋初始爆发阶段，西北冷空气进入温暖的洋面，海洋对上层大气感热输送和潜热释放较强，非绝热加热对气旋快速发展有较大贡献。气旋进一步发展，“T”型锋面结构显著，温度平流净贡献较大，对气旋的发展和维持起重要作用。

英文摘要:

      A super explosive cyclone with frontal "T-bone" structure over the Northern Atlantic from 3 to 6 January 2018 is investigated based on the ERA-Interim data issued by the European Centre for Medium-Range Weather Forecasts (ECMWF), the Geostationary Operational Environment Satellite-EAST (GOES-EAST) infrared satellite data supplied by Cooperative Institute for Meteorological Satellite Studies (CIMSS), and the Weather Research and Forecasting (WRF) modeling results. This explosive cyclone originated over the Gulf Stream and developed rapidly northeastward along the strong gradient of sea surface temperature. It deepened explosively within 6 hours after the cyclogenesis, and its central sea level pressure decreased about 48.7 hPa in 24 h. The upper-level trough, positive vorticity advection and lower-level atmospheric baroclinicity provided a favorable condition for the rapid development of this cyclone. With the rapid development of the cyclone, the relative vorticity in the lower-level increased sharply. The cold and dry air coming from the northwest advanced eastward rapidly in association with a cyclonic circulation, and met with the warm and moisture air coming from the southeast, and frontogenesis enhanced significantly. The warmer sea surface heated of the cold air, that gradient of air temperature decrescent. The weak and eastward cold front became nearly perpendicular to the warm front and formed a frontal "T-bone" structure. The diagnostic analysis based on the Zwack-Okossi equation shows that latent heat release, thermal advection and positive vorticity advection resulted in its explosive development. At the initial developing stage, due to abundant surface heat fluxes and latent heat release, diabatic heating made a great contribution. With the rapid development, the frontal "T-bone" structure was significant. Temperature advection played an important role in the development and maintenance of the cyclone because of its large net contribution.