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浙北沿海连续3次飑线演变过程的环境条件
引用本文:陈淑琴,章丽娜,俞小鼎,徐哲永,刘菡.浙北沿海连续3次飑线演变过程的环境条件[J].应用气象学报,2017,28(3):357-368.
作者姓名:陈淑琴  章丽娜  俞小鼎  徐哲永  刘菡
作者单位:1.浙江省舟山市气象局, 舟山 316021
基金项目:中国气象局预报员专项(CMAYBY2015-096),南京信息工程大学气象灾害教育部重点实验室开放课题(KLME1311),浙江省舟山市一般非海洋类项目(2013C31059)
摘    要:利用雷达和地面加密自动气象站、日本气象厅(JMA)区域谱模式(RSM)再分析资料,对2008年7月2日发生在浙北的连续3次飑线过程(其中第3次在近海生成了弓形回波)进行诊断分析。分别探讨3条飑线发展演变情况和对应的各种环境场条件,侧重对比下垫面温度、湿度、风辐合等条件与对流发展演变的关系,尤其是海陆边界对对流新生与加强的作用。从水平、垂直方向分析第3条典型弓形飑线形成过程中单体的发展、减弱、出流、入流、新单体生成、传播等过程。研究发现,在天气背景相似的小范围区域内,气温高、湿度大之处、锋面、辐合线、海岸线附近容易新生单体和加强对流。强对流系统对下垫面也有反馈作用,进而影响对流系统的发展变化:强雷暴单体的下沉气流在近地面形成冷池,其前侧冷空气向外辐散形成阵风锋,迫使锋前暖湿气流在冷池上抬升,在阵风锋附近产生新的对流单体,形成对流系统的传播。强单体经常在海岸线附近生成、加强,尤其是阵风锋与海岸线相交时。

关 键 词:弓形飑线    下垫面    海陆边界
收稿时间:2016/10/14 0:00:00
修稿时间:2017/4/10 0:00:00

Environmental Conditions of Three Squall Lines in the North Part of Zhejiang Province
Chen Shuqin,Zhang Lin,Yu Xiaoding,Xu Zheyong and Liu Han.Environmental Conditions of Three Squall Lines in the North Part of Zhejiang Province[J].Quarterly Journal of Applied Meteorology,2017,28(3):357-368.
Authors:Chen Shuqin  Zhang Lin  Yu Xiaoding  Xu Zheyong and Liu Han
Institution:1.Zhoushan Meteorological Bureau of Zhejiang Province, Zhoushan 3160212.Training Center of China Meteorological Administration, Beijing 100081
Abstract:Based on radar data and intensive surface observations, combined with JMA reanalysis data, a typical case with three consecutive squall lines is analyzed, which occurred in the north part of Zhejiang Province on 2 July 2008. Corresponding atmospheric conditions are investigated in detail. Special emphasis is given on the relationship between convection current and underlying surface state such as temperature, humidity and convergence of wind, especially the impact of land-sea boundary on rebirth and strengthening of convection current. Besides, the forming processes of the third typical bow echo, including development, attenuation, effluent, inflow, rebirth and dissemination of convection cell are studied in horizontal and vertical direction. After that, favorable conditions for all evolutionary stages and interrelation of three squall lines are summarized.It shows that there are specific places where newly-born convections and convection reinforcements are likely to be found, such as high temperature region, high humidity region, frontal surface, convergence line and coastline. In general, it's favorable for convection when the ground temperature is more than 32℃, the dew point temperature is greater than 23℃, the ground temperature gradient is greater than 0.1℃/km, or the ground level wind shear is greater than 5 m/s. Severe convective systems also react on underlying surface, and then convective systems are influenced as well, severe thunderstorm causes strong divergent outflow and cool pool is formed on ground layer. Cold air in the front of thunderstorm diverges outwards and causes gust front, which lifts the pre-frontal warm and moist. New convective cells develop close to the gust front, so that convective systems can diffuse forward. The question about convective systems' change crossing coastlines is complex. If they move to the sea by day, the temperature of underlying surface will descend and system's intensity would be weaken easily, and the situation will become opposite by night. In addition, the convergence of wind and intensity of convective systems enhance over the sea on account of small frictional forces and strong wind speed. Severe thunderstorm generates and strengthens at coastlines frequently, and particularly at the junction between the gust front and the coastline due to convergence caused by wind discontinuity around coastlines. Finally, the convection weather concept model before the trough is summarized:The area is within the scope of subtropical high before the trough at 500 hPa. There is strong southwest jet and warm wet tongue at low level, which forms unstable stratification. There is a big wind belt at 500 hPa, which forms a larger vertical wind shear from 0 to 6 km level, adding to the potential instability, and a strong convection system is triggered if a cold front comes.
Keywords:bow-shape squall line  underlying surface  land-sea boundary
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