摘要
利用1°×1°的NCEP再分析资料计算螺旋度、湿位涡及各种基本物理量,并结合多普勒雷达资料,对0903号热带风暴莲花外围环流在粤东引发特大暴雨过程进行追踪和诊断分析,探讨此次特大暴雨天气发生、发展的热力学和动力学机制以及雷达回波特征。分析结果表明:台风低槽外围的西南急流为特大暴雨提供了充沛的水汽条件和热力条件;暴雨区上空中低层()θ_(se)/()p>0,存在明显的等θ_(se)陡立面,同时该区上空低层MPV为高负值区,两者结合可见特大暴雨区上空存在强对流性不稳定层结;而低空强辐合、高空强辐散的高低空形势配置、中尺度次级环流以及强烈的旋转上升运动为此次特大暴雨提供了重要的动力机制。分析还表明:高θ_(se)舌和MPV低舌出现叠加的区域和时间与特大暴雨落区和发生时段有很好的一致性;垂直螺旋度中低层正值中心和高层负值中心与特大暴雨中心区域对应较好;强降水最易发生在旋转上升运动迅速加强发展的时间段里;天气雷达在暴洪预报中的运用,有利地追踪了暴雨系统的演变过程,回波特征显示此次特大暴雨是由高降水率配合较长降水持续时间产生。
Based on the high resolution NCEP reanalysis data the helicity,moist potential vorticity（MPV） and some other essential physical quantities were computed,and then combined with Doppler Radar products, the associated thermodynamic and dynamic mechanisms for the occurrence and evolution of an extremely heavy rain in eastern Guangdong caused by the tropical storm（0903） Linfa were analyzed.The results suggested that the southwesterly jet in the periphery of typhoon trough provided abundant moisture and thermodynamic conditions.At mid-low levels over the rainfall region,the equivalent potential temperature （θ_（se）） surfaces were steep and decreased with increasing altitudes,i.e.（？）θ_（se）/（？）p0.Meanwhile at low levels over the same area,the MPV was remarkably high negative.These two conditions indicated a strong convectional instability.Strong convergence at low levels and divergence at high levels,mesoscale circulation and intense rotational ascending motion provided the dynamic conditions.It was also shown that the location and time of highθ_（se） tongue and low MPV tongue overlapped agreed with those of the heavy rain, and the positive center at mid-low levels and negative center at high levels of the vertical helicity were coincided with the rainfall center.Additionally,heavy precipitation tended to take place during the period when the rotational ascending motion rapidly intensified;and the echo characteristics also showed that the extremely heavy rain is produced by the high precipitation rate with long duration of precipitation.
出处
《气象》
CSCD
北大核心
2012年第5期543-551,共9页
Meteorological Monthly
关键词
热带风暴
特大暴雨
成因分析
湿位涡
螺旋度
雷达回波
tropical storm
torrential rain
causative analysis
vorticity
helicity
radar echo
