四川盆地持续性暴雨发生的一类环流特征研究

利用NCEP 1°×1°的资料研究了四川盆地一类持续性暴雨特征,结果表明:(1)在伴有西太平洋副热带高压西伸和其南侧有热带低压系统扰动的大气环流背景下,其水汽供应环流形势体现为东南气流输送,这主要与副高和热带低压系统相互扰动有关,而与大部分造成四川盆地暴雨的西南气流输送有差异。(2)局地涡度的变化对大尺度环流背景场的分布起到重要的作用,在副高西伸稳定的边缘,局地涡度变化为负,在槽区和热带低压扰动区域内,局地涡度变化为正,而局地涡度的正负变化,取决于涡度方程各项的变化大小,在850hPa上,雨区局地正涡度的增加可能与热带低压的局地正涡度输送有关,而这一过程可能主要由正涡度平流来完成。(3)局地正涡度变化范围和中心较好程度上对应着雨区的范围和中心,可以作为一个判断降水落区的预报要素来参考。 

The Study of a Kind of Circulations Characters on Sustaining Heavy Rain in Sichuan Basin

Using NCEP 1°×1°re-analysis data to analyze a kind of circulations character on sustaining heavy rain in Si-chuan basin.The result showed:First, the atmosphere circulations of heavy rain displayed that there was an western pacificsubtropical anticyclone high, tropic low vortex and short through in 500 hPa, and the transportation path of water vapor wassoutheast wind path, which caused by atmosphere circulations with pacific subtropical anticyclone high and tropic low vortexmainly.Second, variations of local Vorticity were essential for development of large scale atmosphere circulations, and varia-tions of local Vorticity were plus in through region and tropic lowvortexregions, but were negative in region of pacific subtropi-cal anticyclone high mainly.In 850hPa, the increment of local Vorticity had relations to plus local Vorticity transportation oftropic lowvortex regions in heavy rain region, to some extent, the physics process of increment was achieved by plus advectionof Vorticity.Third, the range and center of heavy rain was coincident with the range and center of the range and center of localVorticity, therefore, the variations of local plus Vorticity is a useful physic factor to forecast range of heavy rain.