摘要
2018年8月7日和8月10日,陕西省榆林市先后出现了两次局地短时大暴雨过程(以下分别简称"过程I"和"过程II"),过程累积降水量分别为103.4和142.5 mm。利用NCEP再分析资料、常规地面观测数据、卫星云图数据和多普勒雷达数据,对这两次短时大暴雨的环流背景及中尺度特征进行了特征分析。结果表明:(1)过程I是典型的副热带高压外围短波扰动引起的强对流天气,由地面辐合线触发多个小对流单体发展及合并,造成了强烈的对流活动和雷暴,下沉气流造成地面冷池堆积,使地面气温和气压呈明显的正比关系,并与周围暖湿气流形成阵风锋,从而加强对流及触发新对流;短时强降水发生在TBB低值区,中γ尺度强对流云团造成的极端小时降水是造成局地短时大暴雨的主要原因。(2)过程II是冷涡南下冷空气触发的强对流天气,对流强度相对过程I较弱,无雷暴高压产生,地面气温和气压呈一致下降趋势;短时强降水发生在TBB梯度大值区,大暴雨区上游有较强的对流云团东移,经过神木县境内时加强而造成"列车效应",从而造成局地的短时大暴雨。
Two local short-term heavy rainstorm occurred in Yulin on 8 and 10 August(hereinafter referred to as process I and process II)are with the accumulated rainfalls of 103.4 mm and 142.5 mm respectively.Based on data of NCEP reanalysis,automatic observation,FY-2 E satellite and Doppler radar,background circulation and mesoscale characteristics of two process are analyzed in this paper.The results show that:(1)Strong convective weather process I is triggered by short-wave trough in the northwest of subtropical high.Development and integration of small convective cells triggered by surface convergence lines and lead to thunderstorm,causing accumulation of cold pools on the ground.As a result,surface temperature and pressure are inversely proportional to each other.Moreover,short-term strong precipitation is corresponding to areas with low TBB,and extreme hourly precipitation caused by mesoscale-γ severe convective clouds are responsible for short-term heavy rain.(2)Process II is caused by cold air produced by northeast cold vortex moving south,and development of strong convection is less weaker than that of process I,so there is no thunderstorm high,making a positive correlation between surface temperature and pressure.In satellite images,short-term strong precipitation is corresponding to the areas with large gradient of TBB,and convective clouds on the upstream region of Shenmu county moving to east and developing continuously,producing longer “the train effect”and resulting in local short-time heavy rainstorm in Shenmu.
作者
肖贻青
肖湘卉
屈丽玮
XIAO Yiqing;XIAO Xianghui;QU Liwei(Shaanxi Meteorological Observatory,Xi’an 710014,China;Weinan Meteorological Bureau,Weinan 714000,China)
出处
《沙漠与绿洲气象》
2022年第1期32-40,共9页
Desert and Oasis Meteorology
关键词
短时大暴雨
中尺度特征
列车效应
short-term heavy rainstorm
mesoscale characteristics
train effect
