摘要
基于同化多普勒雷达资料的WRF模式、地面加密观测、卫星云图和NCEP再分析资料等,分析总结2015年8月3日、2016年7月24日西安两次致灾短时暴雨过程环境条件、中尺度系统及动力因子指数特征。结果表明:关中处于稳定少动的西太平洋副热带高压西北边缘,上干下湿、午后低层大气超绝热状态,为短时暴雨提供了热力条件。西风槽与近地层切变线是暴雨直接影响系统。伴随冷锋过境,午后西北方向咸阳、铜川一带地面偏北风跃增是短时暴雨有利触发因子,强降水位于地面3 h正变压中心至东侧大梯度区附近。短时暴雨对流云团距离北部高空急流相对较远,无斜压叶状云系特征,降水对上升气流拖曳作用明显,云团TBB中心降至-65℃以下后,周边出现最大雨强。暴雨云团内部,霰粒子含量最大,冰粒子比其他粒子偏少一个量级以上,最强上升运动在霰粒子中心上方-30℃层附近、接近雪粒子中心;伴随整层雨水、霰和雪粒子含量5倍以上突增出现短时暴雨,雪粒子比雨水、霰粒子开始增多时段偏晚约1 h,其含量峰值与最大雨强同步。两次短时暴雨环境条件和中尺度特征差异明显。“0803”过程为切变线冷区暴雨,高空西风急流范围大、位置偏南,西太平洋副热带高压较弱,西风槽后偏北冷空气活跃,偏南水汽输送弱,关中地区中下层存在明显能量锋区和对称不稳定;云团内部冰相粒子明显偏多,雪粒子相对霰粒子占比偏高,冷空气入侵有利于冰相粒子快速生长;暴雨位于能量锋区和对流云团边缘、TBB最大梯度区附近。“0724”过程为切变线暖区暴雨,高空急流范围小、位置偏北,西太平洋副热带高压强盛,偏北冷空气弱,偏南水汽输送明显,关中地区中下层为位势不稳定;云团内部冰粒子偏少,雪粒子相对霰粒子占比低;暴雨位于对流云团内部、TBB中心附近。定义的垂直螺旋度指数VHI和散
Characteristics of mesoscale system and dynamic factor index during disastrous short-time rainstorms that occurred at Xi'an on 3 August 2015(The“0803”process)and 24 July 2016(The“0724”process)are analyzed by using NCEP 1°×1°reanalysis data,ground intensive observation data,satellite cloud data and WRF based on C-band radars data assimilation.Results show that Guanzhong is located in the stable northwest border of the Pacific Subtropical High.Westerly trough and shear line are the direct systems that influence.In the afternoon,upper dry and lower wet stratification with air at lower levels is hyper adiabatic,which provides favorable environment for convection and strong release of unstable energy.Accompanied by the passage of a cold front,jumping of northward wind at surface from northwest Xianyang and Tongchuan in the afternoon is the triggering to rainstorm.Rainstorm is near the 3-hour anallobaric center of the ground to the east side of the great gradient region.The disastrous short-time rainstorm clouds are located far from the northern upper Jet,and their north parts have no baroclinic and leaf-like forms.The rainfall drag effect is evident.TBB center decreases to-65℃during the rainfall peak.Graupel is the most significant particle in the mesoscale convective cloud above middle levels.The strongest upward motion center is located near the-30℃level and snow center,which is just above the graupel center.There exists five times increasing of different particle content in the mesoscale convective cloud when rainstorm begins.The rainfall intensity peak is consistent temporally with that of snow particle content.Environment conditions and mesoscale characteristics are obviously different between the two processes.The“0803”process is near the cold zone of shear line,which features a wide range of upper westerly jet currents,a southerly location,a weaker Western Pacific Subtropical High,an active northerly cold air behind the westerly trough and weaker southward water vapor transport.Meanwhile,ther
作者
张雅斌
罗慧
赵荣
薛谌彬
冉令坤
高宇星
刘波
ZHANG Ya-bin;LUO Hui;ZHAO Rong;XUE Chen-bin;RAN Ling-kun;GAO Yu-xing;LIU Bo(Xi'an Meteorological Bureau,Xi'an 710016,Shaanxi,China;Shaanxi Meteorological Information Center,Xi'an 710014,Shaanxi,China;Shaanxi Meteorological Bureau,Xi'an 710014,Shaanxi,China;Jiangxi Meteorological Observatory,Nanchang 330046,Jiangxi,China;Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China;Meteorological Observation and Technology Support Center of Shaanxi Province,Xi'an 710014,Shaanxi,China)
出处
《热带气象学报》
CSCD
北大核心
2019年第5期614-628,共15页
Journal of Tropical Meteorology
基金
科技部科技基础性工作专项（2013FY112500）
国家自然科学基金（41575065、41861144021）
中国气象局预报员专项（CMAYBY2017-074）共同资助
关键词
短时暴雨
环境条件
中尺度特征
对流云团
WRF模式
动力因子指数
short-time rainstorm
environment conditions
mesoscale characteristics
convective cloud
WRF model
dynamic factor index
