四川盆地北部两次大暴雨过程对比分析  

Comparative Analysis of Two Heavy Rainfall Events in Northern Sichuan Basin

作　　者：王璐思 张晓涵 蒋璐西 侯林松 WANG Lusi;ZHANG Xiaohan;JIANG Luxi;HOU Linsong(Nanchong Key Laboratory of Strong Weather Research in Northern Sichuan,Nanchong 637000,China;Guangyuan Meteorological Service,Guangyuan 628017,China;Ziyang Meteorological Service,Ziyang 641399,China)

机构地区：[1]川东北强天气研究南充市重点实验室,南充637000 [2]四川省广元市气象局,广元628017 [3]四川省资阳市气象局,资阳641399

出　　处：《高原山地气象研究》2024年第4期108-118,共11页Plateau and Mountain Meteorology Research

基　　金：川东北强天气研究南充市重点实验室科技发展基金项目(NCQXKJ202303);广元市气象局数值预报模式检验与应用创新团队项目。

摘　　要：利用常规气象观测资料、融合格点降水资料以及ERA5再分析资料,对四川盆地北部—甘陕南部2020年6月15—17日(简称“20·616”)和2021年6月15—17日(简称“21·617”)两次大暴雨天气过程进行了对比分析。结果表明:(1)两次大暴雨过程均有持续时间2 d、累计雨量大、降水强度大、夜间到上午为强降水集中时段等相同特征,其中“20·616”雨带为移动型,而“21·617”雨带较稳定,前者短时强降水出现站次、降水强度较后者明显偏多、偏强。(2)两次过程均在有利的大尺度环流背景下发生,低层切变线和低空急流是主要影响系统;前者发生在副高东退过程中,属于低槽东移型暴雨,强降水带位于700 hPa偏西南风低空急流左前方和850 hPa偏东南风低空急流头部的两层切变之间;后者发生在副高西伸过程中,属于东高西低型暴雨,强降水带位于700 hPa切变线偏暖区一侧、700 hPa偏南风急流前方以及850 hPa偏北风急流中。(3)“20·616”过程暴雨中心低层正涡度和负散度表现为强的垂直上升运动,与暴雨中心强降水时段吻合,可能与盆地西北部地形抬升使得垂直上升运动增幅有关;“21·617”过程低层正涡度负散度虽较“20·616”过程偏强,但垂直上升运动条件偏弱,且与暴雨中心存在位置偏差。(4)两次暴雨天气过程降水持续的关键是低层两支低空急流源源不断地将海上的暖湿气流输送到盆地北部和甘陕南部,水汽强辐合与强降水的出现时间、落区均吻合。(5)两次暴雨发生前大气均为强不稳定状态,“20·616”强降水出现在能量锋前暖湿气流一侧和θse850能量舌区,“21·617”强降水发生在能量锋区中偏冷空气一侧。Based on the conventional meteorological observation data,the merged grid precipitation data and the ERA5 reanalysis data,two heavy rainfall weather processes in northern Sichuan Basin-southern Gansu and Shaanxi from June 15 to 17,2020(20·616)and from June 15 to 17,2021(21·617)were compared and analyzed.The results show that:(1)The two heavy rainfall processes have the same characteristics of two-day duration,large cumulative rainfall,large precipitation intensity,and strong precipitation concentration period from night to morning.Among them,the“20·616”rain belt is mobile,while the“21·617”rain belt is more stable.(2)The two processes occurred under the favorable large-scale circulation background,and the low-level shear line and low-level jet were the main influencing systems.The former occurred during the eastward retreat of the subtropical high,which was a low-trough eastward-moving rainfall.The heavy rainfall belt was located between the left front of the southwesterly low-level jet at 700 hPa and the two-layer shear at the head of the southeasterly low-level jet at 850 hPa.The latter occurred during the westward extension of the subtropical high,belonging to the east-high and west-low rainstorm.The heavy precipitation zone was located on the warm side of the 700 hPa shear line,in front of the 700 hPa southerly jet and in the 850 hPa northerly jet.(3)The positive vorticity and negative divergence in the lower layer of the rainstorm center in the“20·616”process showed strong vertical ascending motion,which was consistent with the period of heavy rainfall in the rainstorm center,which might be related to the increase of vertical ascending motion caused by the terrain uplift in the northwest of Sichuan Basin.Although the negative divergence of positive vorticity in the lower layer of the“21·617”process was stronger than that of the“20·616”process,the vertical upward motion condition was weaker,and there was a position deviation from the rainstorm center.(4)The key to the persistence of

关 键 词：盆地北部 大暴雨 低空急流 低涡切变 斜压性 

分 类 号：P458[天文地球—大气科学及气象学]