2004年春季两次增温过程及降水的对比分析

利用常规的天气图、卫星云图和物理量诊断对2004年春季两次持续性增温过程及降水天气进行诊断分析,结果表明:两次增温过程的降水强度、范围和落区等差异显著。前者造成了陕西历史上最早的暴雨过程,并有冰雹相伴;后者则为一般性降水。在春季降水过程中,当南海和菲律宾附近有热带低压云系存在时,对陕西的强降水有增幅作用;来自孟加拉湾700 hPa的偏西南急流和来自南海850 hPa的偏东南急流直伸到陕西的位置决定强降水的落区。700 hPa正涡度中心与垂直运动的上升区配合很好,涡度随着暴雨的临近明显增大,正涡度的增长,有利于对流的发展。

A STUDY ON TWO PROCESSES OF THE INCREASE OF TEMPERATURE AND PRECIPITATION IN SPRING OF 2004

Using regular synoptic chart and satellite cloud picture,a diagnostic study in two processes of the increase of temperature and precipitation in spring of 2004 is carried out.The result shows that intensity,range and area of rainfall between two processes are distinctly different.Under the condition of hail,earliest heavy rainfall occurs in Shaanxi province in the preceding process.However,ordinary rainfall occurs in the latter process.The visible precipitation process will occur after the continuous temperature increase on large scale.There exists cloud system of a depression of tropical belt near south China Sea and Philippines,meanwhile,the strong rainfall will be heavier in Shaanxi province.The area of strong rainfall depends on the location of Shaanxi province where lower tropospheric jet from Bengal gulf and South China Sea extends.When heavy rainfall occurs,the area of positive centre of vorticity at 700 hPa matches well with one of the ascending motion.In addition,heavy rainfall nearing vorticity at 700 hPa is augmented markedly,which leads to development of convection.