秦岭地区秋季降水的气候特征分析

An analysis of climate characteristic of rainfall in Qinling in autumn

利用1961—2005年观测资料和NCEP/NCAR再分析资料,对秦岭邻近地区秋季(9—10月)降水的气候特征及其与大气环流关系进行分析,结果表明:秦岭地区秋季降水具有明显年代际变化特征,1960s后期、1970s和1980s初秋季多雨,而1950s和1960s初前期、1980s中后期和1990s秋少雨,2000年以后秋季降水略有增多。秦岭地区秋季雨涝年环流特征是高原北侧高空西风急流偏强,乌拉尔山长波脊稳定,西大平洋副热带高压位置偏西,强度偏强,对流层低层东南风气流和西南风气流为秦岭地区输送了大量水汽;而少雨干旱年则高空高原北侧西风急流偏弱,秦岭地区受青藏高压控制或西北气流控制,与东亚冬季风相联系的偏北气流阻断了偏南气流的水汽输送。

Using observation data from 1961 to 2003 and NCEP/NCAR reanalyzed data, this paper investigates climate distribution of precipitation in autumn during Sep. and Dec. in vicinity of Qinling and drought-flood variation as well as its relationship with atmospheric circulation. It is shown that influenced by the terrain of Qinling, the rainfall amount is obviously higher on its southern side than northern side, but the annual variation of precipitation is consistent on both sides. Over recent 50 years, precipitation decreases in autumn in majority of China, precipitation in Qinling indicated an evident similar trend of decrease. In Qinling, the pluvial year of autumn normally features consecutive rain and concentrated large rainfall amount. Generally, a blocking pattern stabilizes in the westerly jet of mid-high latitude, and the subtropical high pressure locates more westward with stronger intensity, while the southeast monsoon is rather strong. However, the atmospheric circulation of a severe drought year represents the domination of Tibetan high pressure or northwest stream in this area. The powerful southward cold air cuts off the transport of water vapor from the southeast monsoon.