近30年上海地区暴雨的气候变化特征

利用上海地区11个气象站1979-2008年5～9月降水资料分析了近30年上海地区暴雨的年、月际及暴雨成因的变化特征.结果表明:1995年以来,上海地区暴雨逐渐向强、局部、特短时间方向变化.7、8月暴雨较多,以短时局部性暴雨为主;6、9月暴雨次之,6月长和特长暴雨要多于短和特短暴雨,9月反之;5月暴雨最少.从形成上海地区暴雨天气系统的分析表明,静止锋暴雨最多,稳定时能形成持续时间长的强暴雨,不稳定时形成短的弱暴雨;其次是暖区暴雨,它是上海地区形成夏季短时局部性强暴雨的主要天气型;另外,台风、台风切变、台风倒槽、低压、冷锋、暖锋和东风扰动形成的暴雨也占有一定的比例.1995年以来,暖区暴雨整体增加,而静止锋暴雨进入21世纪逐渐减少,这可能主要归因于气候变暖和城市热岛效应.

The Characteristics of Climate Change of Torrential Rains in Shanghai Region in Recent 30 Years

Based on 11 observation stations precipitation data in Shanghai region from May to September during the period 1979 to 2008, the change characteristics of annual and month and genesis of torrential rains in Shanghai region in recent 30 years were analyzed. The results indicate that torrential rains in Shanghai region have turned to strong, local, extremely short-time change trend since 1995. The torrential rains are mainly concentrated from June to September. They occur frequently in July and August, which are mainly short-time and local ones, and arise commonly in June and September, yet, least in May. There are more persistent torrential rains than short-time ones in June, while on the contrary in September. The analysis of weather systems of torrential rain in Shanghai region shows that torrential rains induced by stationary fronts take place most frequently and occur persistent and strong ones when they are stable, otherwise become short-time and weak ones. Torrential rains brought from warm area systems occur second frequently and the kind weather system is a main synoptic type which leads to the short-time and local torrential rain of Shanghai region in summer. Additionally, torrential rains caused by typhoon, typhoon shear, typhoon inverted trough, depression, cold front, warm front and east wind disturbance have a certain proportion. Torrential rains induced by warm area have increased since 1995, but these of stationary fronts have, mainly due to climate warming and heat-island effect, gradually decreased since 2000.