ENSO Modoki与春秋季中国西北地区极端低温的关系

Relationship between ENSO Modoki and extremely low temperature over Northwest China

利用1979-2008年的NCEP/NCAR再分析资料和中国西北地区136个台站的气象资料,研究了ENSO Modoki与春、秋季中国西北地区极端低温的关系.结果表明:当秋季发生El Nino Modoki事件时,次年春季新疆中部、西北部边缘地区及祁连山脉附近的极端低温事件较少,发生La Nina Modoki事件时则相反;当冬季发生El Nino Modoki事件时,次年秋季宁夏、陕西及甘肃中南部地区的极端低温事件较多,而发生La Nina Modoki事件时则相反.另外,500 hPa位势高度场合成分析显示,极端低温事件多发与否,与中国西北地区附近是否有发展旺盛的径向环流有着一定的关系.

NCEP/NCAR reanalysis data and data from 136 weather station in Northwest China were used to establish the relationship between ENSO Modoki and extremely low temperature over Northwest China. A correlation analysis showed that when El Ni？o Modoki occurred in autumn, the number of occurrences of extremely low temperature events would decrease in central Xinjiang, northwest edge of the area and the Qilian Mountains area in the next spring. However, when La Ni？a Modoki occurred in autumn, the situation would be opposite. When El Ni？o Modoki occurred in winter, the number of occurrences of extremely low temperature events would increase in Ningxia, Shanxi, central and southern Gansu in next autumn; when La Ni？a Modoki occurred in winter, the situation would be opposite. Composting analysis of 500 hPa geopotential height field showed that the occurrence of extremely low temperature events relied heavily on exuberant radial circulation near Northwest China.