摘要
利用NCEP/NCAR再分析资料、常规观测资料和大连地区近100个逐时自动气象站雨量资料,对大连地区2007年3月3～5日和2009年4月19～21日两次春季暴雨过程的大尺度环流特征进行了诊断分析,研究了大尺度环流条件对大连地区春季暴雨的影响。结果表明:(1)对流层低层的增温、增湿及中纬度冷空气的侵入,是导致两次春季暴雨的重要条件。(2)气旋生成后若位于长波槽前,有靠近中纬度斜压锋区的趋势,则降水强度大;若无长波槽靠近,并远离中纬度斜压锋区,则降水强度小。(3)若长时间维持低空急流水汽输送通道,将有利于大连地区强降水的产生。(4)南支高空急流的西风动量下传,有利于江淮气旋的生成、发展。在其北上过程中,靠近中纬度高空急流,加大了向东北方向的高空流出气流,有利于气旋的再次增强和维持。(5)高层强湿位涡向低层下传,使冷空气侵入气旋外围,锋生的强迫作用,加剧了暖湿气流的上升。强湿位涡下传与地面正涡度区连通,加大了局地的位涡扰动,有利于低层锋区诱生出气旋环流,促使气旋发展、加强,导致强降水的产生。(6)摩擦耗散损失的能量从高层环流背景中的非地转运动和气压梯度力做功获得动能补充,有利于降水强度增大。因此,春季在江淮气旋生成并东北移的过程中,可从上述诸因子初步判断气旋是发展还是减弱,并预报降水的强弱。
Using NCEP/NCAR reanalysis data,conventional observation data,and hourly rainfall observation data from nearly 100 automatic weather stations（AWS） in Dalian,the characteristics of the large scale circulation associated with the two heavy rainstorms processes in Dalian during 3～5 March 2007 and 19～21 April 2009 are diagnostically analyzed.The results show that：（1） Increasing of temperature and moisture in the lower troposphere,and intrusion of cold air from the mid-latitude region are the important conditions to result in the two torrential rain occurrences in spring;（2） Rainfall intensity is enhanced after the cyclone genesis which located in front of a long-wave trough,and tends to move close to the baroclinic frontal zone in the mid-latitude region,and is opposite when no long wave trough is nearby and the mid-latitude baroclinic frontal zone is far distant away;（3） It is favorable for occurring of heavy precipitation in Dalian area this has the long time link this area with the moisture transport channel from lower level jets;（4） Downward propagation of westerly momentum in the southern branch of the upper level jets is favorable for genesis and development of cyclone over Yangtze-Huaihe River valleys.During its progressing northward,the jets move close to the upper level jets in the mid-latitude region,leading to enhanced divergent flow in the upper layer in the northeast of Dalian.Such flow pattern is favorable for re-intensification and long time substation of the cyclone;（5） Propagation of strong moist potential vorticity from upper to lower levels leads to intrusion of cold air into the periphery of the cyclone,and genesis of front.Forcing by frontal genesis enhances uplift of warm and moist flow.Downward propagation of strong moist potential vorticity is channeled with positive vorticity at the surface,thus the amplifies local perturbation of potential vorticity,and induces favorably cyclonic circulation in the frontal zone of lower layer.The cyclonic circulation will force the cyclone to develop and strengthen,and result in heavy precipitation occurrences.（6） Supplement of dynamic energy acquired from the ageostropic movement in the large scale circulation in middle and upper layers to the energy loss by frictional dissipation amplifies precipitation intensity.Therefore,during the genesis and northeastern movement of cyclone over Yangtze-Huaihe River valleys in spring,from extension of the moisture channel to Dalian area,relationship of cyclone with baroclinic frontal zone,and interaction between upper and lower level jets are identified the cyclone will develop and intensify or rapidly weaken,thus to forecast precipitation intensity indicatively.Different intensities of cold air result in different amplifications of temperature decrease.The rapidly decreasing of temperature will bring about precipitation form of multiple phase changes,which is easily induce extremely severe weather events which is directly linked to hazard.During the heavy precipitation in spring,attention might be focused not only on rainfall amount,but also on rapid changes of phases of water.
出处
《高原气象》
CSCD
北大核心
2011年第5期1243-1254,共12页
Plateau Meteorology
基金
大连市科技计划项目(2009E12SF167)
中国气象科学研究院基本科研业务费专项(2007Y006)共同资助
关键词
大连
春季暴雨
湿位涡
环流特征
Dalian
Spring rainstorm
Moist potential vorticity
Circulation characteristic
