中国东南沿海冬季渐近线型锋生辐合线及其强降水的发展机制
投稿时间:2018-10-06  修订日期:2018-12-30  点此下载全文
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王坚红 南京信息工程大学 气象灾害预报预警与评估协同创新中心, 江苏 南京 210044
南京信息工程大学 海洋科学学院, 江苏 南京 210044 
1597706505@qq.com 
曲梓祎 南京信息工程大学 海洋科学学院, 江苏 南京 210044
锦州市气象局, 辽宁 锦州 121000 
 
李洪利 南京信息工程大学 海洋科学学院, 江苏 南京 210044  
黄志刚 福建省气象服务中心, 福建 福州 350001  
张翠艳 锦州市气象局, 辽宁 锦州 121000  
苗春生 南京信大气象科学技术研究院, 江苏 南京 210044  
基金项目:国家自然科学基金资助项目(41276033;41805033)
中文摘要:基于中国东南沿海冬季强降水的统计分析,采用EOF、REOF、North检验等方法对2011—2016年冬季(12、1、2月)欧洲中期天气预报中心降水资料进行分类,选取位于内陆的第1、第4 REOF模态,对该两模态的降水样本进行合成分析,合成的降水中心与东南沿海福建的多年统计暴雨中心吻合。与强降水相配合,1 000 hPa上有自北向南的渐近线型辐合气流,并伴有锋区,从而形成天气尺度渐近线型锋生辐合线,强降水位于辐合轴线左侧气旋式风切变处。这是一类以前未曾受到关注和讨论的东南沿海地区冬季暴雨系统。利用客观判定方法和建立系统坐标系,以确认并诊断该系统的结构。在冷干少雨、低层盛行偏北风的冬季,此类系统兼有锋区热力抬升与辐合气流动力抬升,在雨区形成旺盛的上升运动;同时,通过辐合线正交风分量将邻近的海面水汽汇集到降水区,与中高层副高边缘偏南气流相向而行,构成较为深厚的交汇式水汽输送层;通过非绝热加热,形成深厚的热力对流不稳定,并通过干区向湿气团下楔入,形成下干上湿的湿动力不稳定,以及假相当位温随高度增加而递减,形成上暖湿、下冷干的对流不稳定层。因此,该系统对冬季强降水的发生发展及落区具有重要影响。通过WRF模式的模拟结果探讨环境热力机制的影响,结果显示,凝结潜热加热可影响辐合线的辐合位置和强度、锋生区的位置及强度,进而影响系统的活跃程度。中层潜热加热抑制平流感热冷却进入暖气团,维持降雨区的热力不稳定和降水强度。渐近线型锋生辐合线有利于东南沿海冬季大范围降水出现暴雨,其中凝结潜热释放具有重要贡献。
中文关键词:中国东南沿海冬季强降水  渐近线型锋生辐合线  交汇式水汽输送层  数值模拟  热动力机制
 
Thermodynamic mechanism of asymptotic frontogenesis convergence line and its heavy rainfall in southeast coast of China in winter
Abstract:Based on the statistical analysis of heavy precipitation in southeast coast of China in winter (December,January and February),the European Center winter precipitation data during 2011-2016 were classified by the EOF,REOF and North test methods,and the first and fourth REOF modes located inland were selected.The composite analysis of precipitation samples of the two modes shows that the composite precipitation centers are consistent with the multi-year statistical rainstorm centers in Fujian province.In combination with the heavy rainfall,there is an asymptotic convergence flow from north to south with a front zone at 1 000 hPa,which forms a synoptic scale asymptotic frontogenesis convergence line.The heavy precipitation is usually located on the left side of convergence axis where a cyclonic wind shear exists.This is a type of winter rainstorm system in southeast coast of China that has not been specifically concerned and discussed in the past.The structure of the rainstorm system is confirmed and diagnosed by an objective determination method and establishing a coordinate system of the system.In the cold and dry winter with less rain and prevailing northerly wind at the low level,this kind of system has both the thermal uplift in the front area and the dynamic uplift of convergence air flow,forming a vigorous ascending motion in the rain area.Meanwhile,through the orthogonal wind component of convergence line,the water vapor from adjacent sea surface is collected into the precipitation area,combined the southerly airflow at the west edge of the subtropical high at the middle and upper levels,forming a relatively deep confluence water vapor transport layer.By the non-adiabatic heating,the deep thermal convection instability is formed.Through the dry area wedging under the moisture mass,the wet dynamic instability of the lower dry and upper wet is formed,and the pseudo-equivalent potential temperature decreases with the increase of height,forming a convection instability layer of the upper warm wet and the lower cold dry.Therefore,the system has an important impact on the occurrence and development and the falling area of heavy rainfall in winter.The influence of environmental thermal mechanism is discussed by the simulations of WRF model.Results show that the condensation latent heat heating can affect the convergence position and intensity of the convergence line,the position and intensity of frontogenesis area,and then affect the activity of the system.The latent heat heating in the middle levels can prevent the advection sensible heat cooling into the warm air mass,and maintain the thermal instability and precipitation intensity in the rainfall area.The asymptotic frontogenesis convergence line is conducive to the occurrence of heavy rain in the large-scale precipitation in Fujian in winter,in which the condensation latent heat release plays an important role.
keywords:winter heavy precipitation in southeast coast of China  asymptotic frontogenesis convergence line  confluence water vapor transport layer  numerical simulation  thermodynamic mechanism
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