长江中下游一次暴雨过程的湿Q矢量诊断分析

Diagnostic Analysis of Wet Q-Vector for a Rainstorm Process in the Middle and Lower Reaches of Yangtze River

利用中国国家级地面气象站基本气象要素日值数据集(V3.0)和欧洲中心1°×1°的再分析资料,对2016年夏季长江中下游地区的一次暴雨过程的湿Q矢量进行了诊断分析。研究结果表明:此次暴雨过程中,雨带始终呈东北西南带状分布,累计降水量最大值在450 mm以上,具有降水历时长、总量大、强度大、降水集中、雨带稳定的特点。中低层非地转湿Q矢量散度场(700 hPa、500 hPa)能较好地表现出暴雨落区的分布特征,其负值区可作为预报降水的有利工具,但总体来说500 hPa的诊断效果不如700 hPa的好。此次暴雨过程都伴有明显的上升运动,尤其7月1-3日整个大气上升运动更为明显,对流活动旺盛,对应1 3日的降水强度也很大。垂直运动的上升区与湿Q矢量散度的负值区始终保持一致,并与暴雨区对应较好。Qx^*和Qy^*的正负值在东西方向上相间排列,暴雨区上空是Qx^*和Qy^*正负值的交汇处,而交汇处是两个次级环流圈共有的上升气流区,上升气流携带低层的暖湿空气,为此次暴雨过程创造了有利的水汽辐合条件,有利于暴雨的形成和维持。

The wet Q-vector of a rainstorm in the middle and lower reaches of the Yangtze River in the summer of 2016 was analyzed by using the daily data set of basic meteorological elements for China Nation Surface Meteorological Stations(V3.0)and the 1°×1°reanalysis data of ERA-Interim.The results show that during the rainstorm process,the rain band has always been distributed along the northeast-southwest belt.The maximum amount of precipitation is more than 450 mm,which has the characteristics of long duration,large total amount,high intensity,concentrated precipitation and stable rain band.The ageostrophic wet Q-vector divergence field in the middle and lower layers(700 hPa,500 hPa)can well show the distribution characteristics of the rainstorm area,and its negative value area can be used as a useful tool for forecasting precipitation.But in general,the diagnostic effect of 500 hPa is not as good as that of 700 hPa.The rainstorm process is accompanied by obvious upward movement,especially the whole atmosphere upward movement on July 1—3 is more obvious,convective activity is strong,corresponding to the rainfall intensity on July 1—3 is also very strong.The ascending area of vertical movement is consistent with the negative value of wet Q-vector divergence,and corresponds well with the rainstorm area.The positive and negative values of Qx^* and Qy^* are arranged in the east-west direction.Over the rainstorm area is the intersection of the positive and negative values of Qx^* and Qy^*,which is the common updraft zone of the two secondary circulation circles.The updraft will carry the warm and humid air of the lower layer,which creates favorable water vapor convergence conditions for the rainstorm process,and is conducive to the formation and maintenance of rainstorm.