摘要
利用地面观测站降水资料和NCEP/NCAR逐日再分析资料,对2011年初夏(5-6月)发生在长江中下游地区旱涝急转前后的降水异常及相应的环流和水汽条件进行分析。结果表明,在旱涝急转前,中国整个东部均无明显降水;急转后沿长江以南降水异常偏多,而长江以北和华南等地降水偏少。旱涝急转前后东北地区的冷涡由偏西移动到偏东,西太平洋副热带高压由偏弱转变为偏强,脊线由西伸偏南转为东退北抬;长江中下游地区低层先受西北气流控制,随后在东北冷涡的作用下,受西北干冷气流和西南暖湿气流共同影响,为洪涝的发生提供有利的水汽条件;高层200 hPa上,长江中下游地区逐渐由急流出口转变为急流入口。在高低空急流的耦合下,对流层中层的上升运动明显,上升速度最大值位于500 hPa附近,为持续降水的发生提供动力条件。
Based on surface station rainfall data and NCEP/NCAR daily reanalysis data, precipitation anomaly and its corresponding dynamic factors and moisture sources during the period around abrupt alternation of drought and flood in the middle-lower reaches of the Yangtze River from May to June 2011 were analysed. The results show that before the alternation, there＇s no obvious precipitation in all east parts of China, but after that, more rainfall in regions south of the Yangtze River while still less rainfall in north of the river and south of China. Be- fore and after the alternation, northeast cold vortex shifts eastward, west Pacific subtropical high turns from weakness to strength, and its ridge line propagates from southwest to northeast. In the lower troposphere, north- westerly prevails in the middle-lower reaches of the Yangtze River. Both the northwesterly flow which is dry and cold and southwesterly flow which is warm and wet contribute to the flood. On 200 hPa, the entrance of a jet stream in the middle-lower reaches of the Yangtze River turns into an exit. The ascending motion in middle trop- osphere is caused by the interaction between high and low level jets with its maximum speed located on about 500 hPa, which provides dynamic condition for the persistent precipitation.
出处
《高原气象》
CSCD
北大核心
2014年第1期210-220,共11页
Plateau Meteorology
基金
国家重点基础研究发展规划项目(2012CB955204)
国家自然科学基金项目(41275095)
江苏省普通高校研究生科研创新计划(CXZZ11_0608)
关键词
降水异常
旱涝急转
大气环流
长江中下游
Middle-lower reaches of the Yangtze River
Precipitation anomalies
The abrupt alternation ofdrought and flood
Atmospheric circulation
