广州春季降水的变化及其前兆信号

THE VARIATION AND PRECURSOR OF GUANGZHOU SPRING RAINFALL

关键词:  广州春季降水  春旱  前兆信号  副热带高压  低层风场

Key words:  Guangzhou spring rainfall  spring drought  precursor  subtropical high  low wind

摘要:

广州春季降水存在以准2年为主的年际变化和以30年为主的年代际变化,目前处于年代际尺度上的少雨时段。Niño3区的海温异常是广州春季降水最强的前兆信号,它与广州春季降水的显著正相关在前一年的11月份就已出现,并且一直稳定维持到4月份。前冬Niño3区海温异常对广州春季降水的影响是通过影响春季北太平洋副热带高压和低层风场异常实现的。前冬Niño3区海温正异常时,春季副热带高压偏强、位置偏西,华南处于副高边缘垂直运动的上升区,菲律宾以东的低层反气旋环流增加了向华南的水汽输送,从而使得广州春季降水偏多;前冬Niño3区海温负异常时,副热带高压偏弱、位置偏东,华南地区远离副高、处于垂直运动的下沉区,菲律宾以东低层为气旋环流控制,华南地区盛行偏北气流,不利于水汽的向北输送,从而使得广州春季降水偏少,造成春旱。

Abstract:

Guangzhou spring rainfall mainly exhibits interannual variation of Quasi-biannual and interdecadal variation of 30 yrs,and is in the period of weak rainfall at interdecadal time scale.SST anomalies(SSTA) of Nino3 are the strongest precursor of Guangzhou spring rainfall.They have significant positive correlation from previous November and persist stably to April.Nino3 SSTA in the previous winter affects Guangzhou spring rainfall through North Pacific subtropical high and low wind in spring.When Nino3 SSTA is positive in the previous winter,spring subtropical high is intense and westward,South China is located in the area of ascending airflow at the edge of the subtropical high,and water vapor transporting to South China is intensified by anticyclone circulation to the east of the Philippines.So Guangzhou spring rainfall is heavy.When Nino3 SSTA is negative,the subtropical high is weak and eastward,South China is far away from the subtropical high and is located in the area of descending airflow,and water vapor transporting to South China is weak because low-level cyclonic circulation controls areas to the east of the Philippines and north wind prevails in South China.So Guangzhou spring rainfall is weak and spring drought is resulted.