2017年春季我国主要气候特征及其成因分析

Features and Causes for the Climate Anomalies in Spring 2017

2017年春季,全国平均降水量139.1 mm,接近常年同期。从空间分布看,我国降水总体呈"西多东少"的分布型。全国平均气温11.1℃,较常年同期偏高0.7℃,全国大部地区气温接近常年同期或偏高。太平洋年代际涛动处在正位相,春季赤道中东太平洋海温正常略偏暖是造成中国春季气温偏暖的重要气候背景。同时.500 hPa高度和距平场上,亚洲北部(30°N以北)整体呈纬向型环流,东亚大槽位置偏东,全国大部主要受高度场正距平控制,从而有利于春季气温整体以偏暖为主。另外,1月赤道中东太平洋为弱的冷海温,其两侧的副热带地区和西太平洋均为暖水控制的异常分布,有利于出现春季华南和东北降水偏少,西南降水偏多的第二模态分布型。东北大部、华南和江南等地受北风距平控制,水汽以距平辐散为主,降水偏少;西南地区为来自孟加拉湾的暖湿气流与高原外围偏北气流交汇区,水汽异常辐合造成该地区降水偏多。

During the spring 2017, precipitation averaged over China is 139. 1 mm, close to normal. The spatial distribution presents the ＂more in west and less in east＂ anomalous pattern. The spring tempera- eastern Pacific is lower than normal, accompanied by warm SST anomalies at over the subtropical Pacific and West Pacific Region, which is good for less precipitation in South China and Northeast China, and more precipitation in Southwest China during the following spring. For the internal causes, Northeast Chi- na, South China, and Jiangnan Areas are dominated by the north wind and water vapor divergent anoma- lies, which may lead to the less precipitation in these regions. However, warm water vapor from the Bay of Bengal encounters with the north cold wind from the plateau, producing more precipitation over the Southwest China. This is another major cause for the circulation anomaly in 2017.