论文部分内容阅读
利用多种资料从大尺度大气环流、水汽输送、热带海表温度、北极涛动、平流层极涡等方面分析了2012—2013年中国西南地区秋、冬、春季持续干旱的成因。结果表明,西南水汽输送偏弱、高纬度地区南下冷空气路径偏东、冷暖空气难以在西南地区上空交汇,是此次持续干旱的直接原因。这段时间西南地区大都受平直西风气流控制,孟加拉湾和中南半岛地区位势高度较常年偏高,不利于这些地区气旋性环流的发展;热带海表温度异常变化,特别是冬春季印度洋海表温度的持续偏高,使得菲律宾地区上空低层反气旋异常环流增强。这些都导致了西南向水汽输送偏弱。此外,北极涛动异常变化对西南地区的干旱也有重要影响,北极涛动持续处于负位相,不仅使南支槽减弱变浅,西南水汽输送减少,还导致贝加尔湖高压脊偏弱,使北方南下冷空气主体偏东。冬季平流层极涡强度的变化在各个高度的位势高度场和位势涡度场上都有体现,其变化对冷空气的强度及路径有明显影响。
The causes of persistent drought in autumn, winter and spring in southwestern China from 2012 to 2013 were analyzed from various aspects such as large-scale atmospheric circulation, water vapor transport, tropical sea surface temperature, Arctic oscillations and stratospheric polar vortex. The results show that the southwest water vapor transport is weak, and the southward cold air path in the high latitudes is eastward, and the warm and cold air is hard to cross above the southwestern regions, which is the direct cause of this continuous drought. During this period, most of the southwestern region was controlled by the straight westerly winds. The geopotential height over the Bay of Bengal and Indochina Peninsula was higher than normal, which hindered the development of cyclonic circulation in these areas. The anomalous changes in the tropical sea surface temperature, especially the winter and spring Indian Ocean Sea Surface Continued high temperatures led to an enhanced anomalous low-level anomalous circulation over the Philippines. These have led to the weak southwest to the transport of water vapor. In addition, changes in the Arctic oscillation anomalies also have an important impact on the drought in southwest China. The Arctic oscillations continue to be in a negative phase, which not only weakens the south branch channel and reduces the water vapor transport in the southwest, but also leads to the weakening of the ridge of high pressure in Lake Baikal, The main body east of the air. The variation of winter polar stratospheric polar vortex intensity is reflected in the geopotential height field and the potential vorticity field at all altitudes, and the changes have obvious influence on the intensity and path of cold air.