2001-2010年辽宁区域性暴雨阶段性特征

利用辽宁自动气象站逐小时降水资料和1°×1°NCEP资料,对2001-2010年汛期共25次辽宁暴雨过程进行分析,以期得到暴雨过程时间分布特征和典型影响系统.结果表明:25次辽宁暴雨过程中有7次为阶段性暴雨即两段持续性暴雨过程中间有明显的降水减弱与天气系统转换,占总数的28%;辽宁暴雨过程高层(以200 hPa为代表)...

Temporal distribution character of regional heavy rain from 2001 to 2010 in Liaoning province

Based on the hourly precipitation data from automatic weather stations in Liaoning province and the NCEP data (1°×1° resolution), the 25 heavy rain events in the flood seasons from 2001 to 2010 were analyzed in order to obtain the temporal distribution characteristics and typical weather systems of the heavy rain events. The results show that among the 25 heavy rain events, 7 events (28%) have two main rain phases, i.e. there are obviously decreasing precipitation and transformation of weather system between two rain phases. The upper air jet stream is the main weather system at high level (200 hPa) during the heavy rain process. 92% of main weather systems are upper trough at middle level (in 500 hPa). Among 92%, the common influence of upper trough and subtropical high accounts for 57%. 88% of inducing systems is a shear line of the top (or eastern) of cyclone (or inversion trough) at low level (in 800 hPa), and 12% is a shear of saddle field. In general, the weather systems of heavy rain events with two rain phases at high and middle levels do not change in the two stages. The main weather systems are upper jet stream in high level and the common influence of upper trough and subtropical high in middle level (a few of them are only influenced by upper trough). The heavy rain processes with two rain stages are accompanied with the adjustment of the elements fields at low level, especially the adjustment of wind field, which results in the transformation of weather systems at low level or the change of intensity. The adjustment stage of the elements fields at low level is also the interval period of two rain phases. The collocation of weather system and duration of the heavy rain process do not have obvious characteristics for the heavy rain events with two rain stages. That is to say, the heavy rain events in their early period could not be identified whether they could develop into two or more stage rain. 17 events in Dandong and Benxi have the phenomena of abruptly increasing precipitation among 25 heavy rain events, which is related to the location of two cities, namely, Benxi is located in the southeastern Changbai Mountain and the southeast of Dandong is close to the sea.