一次冬季江淮气旋逗点云区的雷达回波和气流结构分析

Radar echo and airmass structure of the comma head within a Jiang-Huai cyclone in winter

中文关键词:  江淮气旋  暴雨(雪)  气旋逗点头  拉格朗日轨迹

英文关键词:Jiang-Huai cyclone  Heavy rain (snow)  Comma head of cyclone  Lagrangian trajectory

中文摘要:

      2016年2月12—13日，受冷空气和江淮气旋暖锋锋生影响，山东出现一次极端暴雨雪天气过程，全省有42个站的降水突破同期历史记录。采用多种观测以及WRF模式模拟的热力学变量，基于拉格朗日方法的气流轨迹模式（HYSPLIT v4.9），分析了气旋逗点云区云系的演变特征、降水不同阶段气旋逗点云区气流结构和轨迹特征。结果表明：（1）江淮气旋逗点云区由4条带状回波合并发展形成，气旋形成后降水回波呈气旋式旋转、拉长，形成多条中尺度强降水带。（2）降雨阶段气旋逗点头从下到上主要由来自东海、黄海、日本海或内陆的边界层气团，来自中国南海和中南半岛的暖湿气团以及来自西亚和东欧的干冷气团组成。气旋逗点头内有3个降水区：北部和南部暖湿气团浅薄、层结稳定，为层状云降水区；中部暖湿气团深厚，中高层有条件性不稳定发展，为深厚的对流云降水区。气旋逗点头中南部的干冷空气来自高层的西亚气团，而剖面北部有来自中层（即青藏高原东部气团）的干冷空气，气团明显变性，对降水贡献大。（3）降雪阶段气旋逗点头从下到上主要由西伯利亚气团、东海气团、南海气团和孟加拉湾气团叠置而成。气旋逗点头西部层状降水区分两部分：北部为降雪区，南部为降雨区。降雪与降雨阶段的明显差别是冷湿的东海气团下面是否有西伯利亚冷气团。降雪区西伯利亚气团上空东海气团深厚，南海气团浅薄；降雨区南海气团深厚，东海气团浅薄。

英文摘要:

      An extreme rainfall-snowfall event that occurred in Shandong province on 12-13 February 2016 due to the influence of the warm front associated with a Jiang-Huai cyclone. Precipitation at 42 stations in Shandong province broke their historic records. Using various observation data and thermodynamic fields simulated by the WRF model and the airflow trajectory model based on the Lagrangian method (HYSPLIT_4.9),this paper analyzes the cloud evolution, airmass structure and trajectory characteristic of comma head within the Jiang-Huai cyclone during different precipitation stages. Main results are as follows. (1) The comma head of the Jiang-Huai cyclone developed from four banded echoes. The radar echo rotated cyclonically and elongated, forming a number of strong mesoscale precipitation bands after the formation of the cyclone. (2) The comma head consisted of three vertically stacked air masses during the raining stage, i.e., from bottom to top, the boundary layer air mass from the East China Sea, the Bohai Sea or from the inland region, the warm-moist air mass from the South China Sea, and the cold-dry air mass originating from western Asia and eastern Europe. There are three rainfall zones within the comma head of the Jiang-Huai cyclone. The northern zone and southern zone, where warm-moist air was shallow and the stratification was stable, was characterized by stratiform precipitation. The middle zone, where warm-moist air was deep and conditional instability developed in the middle and upper levels, was marked by deep convective precipitation. The dry air over the southern and middle zones originated from high level airmass over western Asia, while that in the northern zone originated from mid-level airmass in the eastern Tibetan Plateau, which later transformed into moist air and contributed greatly to rainfall. (3) During the snowfall stage, from bottom to top, the comma head consisted of four vertically stacked air masses that originated from the Siberia, the East China Sea, the South China Sea and the Bay of Bengal, respectively. There were two precipitation zones within the western area of stratiform precipitation:snowfall in the northern zone and rainfall in the southern zone. Whether the cold Siberia air mass existed under the cold-moist East China Sea air mass determined the precipitation in snow or rainfall phases. In the snowfall area, the air mass originating from the East China Sea was deep and the air mass originating from the South China Sea was shallow, while the opposite was true in the rainfall area.