2006年杭嘉湖平原夏秋天气异常分析

2006年杭嘉湖平原出现夏季特长、秋季极短,梅雨量极少、高温天数多、夏旱连秋旱的气候异常现象,对大气环流进行分析发现,西太平洋副高持续偏强偏西,北半球极涡偏弱,冷空气活动偏北,亚洲地区盛行纬向环流.区域气候的异常与大气环流的季节转换异常有关,并且大气环流的异常可以追溯到其前期环流的异常.2006年前冬和春季中高纬度较强的经向环流和持续偏强的副热带高压使得该年夏季副高继续偏强,并且春季的这一环流异常现象,导致秋季大气环流向冬季过渡较快.对涡动高度的分析表明,5月平流层正中心的异常两移、6～7月平流层持续分裂出两个正中心,以及9月正中心的异常增强,预示和促进了夏季低层大气环流的异常发展,从而夏季偏长、夏秋季节转换推迟;11月冷低压的异常增强南压和暖高压的突然减弱,使秋冬季节转换较快,从而秋季极短.

Analysis of Abnormal Summer-Autumn Climate over Hangjiahu Plain in 2006

There appeared some abnormal climatic phenomena such as extra long summer time and short autumn, less rain in Meiyu season, more high temperature days and continuous drought from summer to autumn in the Hangjiahu plain in 2006. Through analyzing the atmospheric circulation, it is found out that the subtropical high was stronger and more westward persistently in the West Pacific; the polar vortex was weaker than normal in the Northern Hemisphere; cold air activities were more northward and the zonal circulation prevailed in Asia in 2006. The regional abnormal climate relates to the abnormal season transition of atmosphere circulation. The abnormal atmosphere circulation can attribute to the early abnormal circulation. The continuously stronger subtropical high in the summer of 2006 is related to the stronger meridional circulation and continuously stronger subtropical high in the previous winter and spring, and the abnormal spring circulation led to the quick season transition from autumn to winter. The result of eddy height analysis shows that the abnormal westward movement of the positive eddy height center in the troposphere in May, the two positive centers generated in the stratosphere from June to July, and the abnormal stronger positive center in September altogether indicated and promoted the abnormal development of the lower level atmospheric circulation in summer; therefore, the summer was longer and the transition from summer to autumn was put off; and the abnormal stronger, southward cold low and the sudden weakening of the warm high in November of 2005 led to quick transition from autumn to winter and short autumn.