安徽省“清明时节雨纷纷”之气候论证

Climatic Demonstration of“Qingming Festival with Endless Rain”in Anhui Province

利用安徽省79个气象观测站自建站至2014年逐日(20时—20时)降水资料,对清明时节降水发生概率的空间分布进行了分析,并选取全省无降水和大范围降水发生的典型年份,对典型年份的环流形势等方面进行综合分析。结果表明,1)安徽省清明时节发生降水的概率呈"南高北低"的空间分布,降水概率大于2/3的区域主要位于安徽省大别山区南部、江淮之间南部到江南地区。2)无降水发生时安徽上空对流层高层为辐合区,中层受东亚大槽后的西北气流控制,并存在明显的下沉气流,受其影响底层比湿相对较低,这些因素均不利于降水的发生。3)大范围降水发生时,对流层高层辐散,在中层西南暖湿气流和暖平流的共同影响下,安徽及其以南地区对流层中层存在较强上升运动,为降水发生提供动力条件;对流层底层来自中国南海的西南暖湿气流较强,并在安徽及其以南地区辐合,为降水发生提供水汽条件。

Based on the daily precipitation data of 79 meteorological stations in Anhui province, the spatial distribution of precipitation probability during Qingming festival is analyzed firstly. Then circulation situations for the typical years of non precipitation weather and large scale rainfall in the day of Qingming festival are discussed, respectively. The results show that： 1） The spatial distribution of Anhui precipitation probability during Qingming festival presents higher level in the south than in the north. The regions where precipitation probability is greater than two thirds are mainly located at southern part of Dabie mountain area and south of Jianghuai to Jiangnan. 2） When no precipitation occurs, upper troposphere above Anhui exists convergence zone, the middle troposphere is controlled by northwest wind behind East Asia trough, and the downdraft is obvious, which can bring lower specific humidity. Thus, precipitation is difficult to occur. 3） When large scale precipitation occurs, the air flow of upper troposphere diverges. Under the simultaneous impact of southwest warm and moist air flow and warm advection, middle troposphere above Anhui and south of it presents strong ascending motion, which provides dynamical condition for precipitation. Moreover, warm and moist southwest air flow from the South China Sea converg over Anhui and south of it can offer moisture condition for precipitation.