山东近海温带气旋强南向大风的特征分析

Characteristic analysis of the strong southerly winds of extratropical cyclones over the Shandong offshore

利用站点观测、历史天气图和NCEP/NCAR的再分析资料,对近40年(1971-2010年)山东近海强南向大风的气候特征和温带气旋造成强南向大风的因素进行了分析。通过统计山东沿海6个代表站点40年的7级以上南向大风,表明:近40年山东近海强南向大风年日数基本呈逐渐减少的趋势,1991年以后年大风日数明显减少,强南向大风主要出现在春季和夏初;统计2000-2010年山东近海强南向大风的个例,发现,温带气旋造成山东近海强南向大风可分为北方气旋(蒙古气旋、黄河气旋)和南方气旋(江淮气旋、黄淮气旋)。分析两类气旋造成强南向大风的因素表明:气压梯度、850 hPa及以下急流和850 hPa暖平流是造成强南向大风的重要因子,3小时变压、500 hPa高空急流和暖平流是次要因子,但气旋在地面气压场配置、3小时变压分布、低空暖平流强弱等方面存在差异。

Based on in-situ observations,weather charts and NCEP/NCAR daily reanalysis data, the characteristics of strongsoutherly winds caused by extratropical cyclones during the recent 40 years （1971 to 2010） over the Shandong offshore areanalyzed. The results show that the number of days of strong southerly winds over the Shandong offshore in the recent 40years has a gradually decreasing trend.After 1991, strong southerly wind days every year significantly are reduced. The strongsoutherly winds occur mainly in spring and early summer. Extratropical cyclone weather systems causing strong southerlywinds over the Shandong offshore are divided into northern cyclones （Mongolia cyclone, the Yellow River cyclone） andsouthern cyclones （Jianghuai cyclone, Huang Huai cyclone）. The pressure gradient, the low air jet under 850 hPa and the 850hPa warm advection show important effects to strong southerly winds caused by extratropical cyclones. The 3 hour variablepressure, the upper air jet at 500 hPa and the 500 hPa warm advection show less important effects. But the distribution ofsurface pressure, the 3 hour variable pressure and the strength of the low warmair have differences.