义乌市降水变化特征分析

根据历史和实测资料的统计分析，得到义乌市的降水变化特征。结果表明：丰水期义乌市的涝年偏多，旱年偏少，而枯水期则旱年偏多，涝年偏少。厄尔尼诺事件的当年或翌年，义乌市的降水显著偏多，而拉尼娜事件的当年或翌年，义乌市的降水则显著偏少。丰水期平均入梅日偏早，平均出梅日偏晚，平均梅雨日数偏长，平均梅雨量偏多，而在枯水期则反之。义乌市6月6—15日入梅的可能性最大，出梅日期的时间分布相对比较分散，其集中期的发生规律不如入梅集中期明显。厄尔尼诺事件的当年或翌年，义乌市的出梅日偏晚，而拉尼娜事件的当年或翌年，义乌市的出梅日偏早。研究结果可为水库源区雨季的人工增雨作业提供科学依据。

Characteristics of precipitation in Yiwu,Jiangsu province

According to the historical and observed data of precipitation, the characteristics of precipitation in Yiwu were analyzed by statistical method. The results indicate that there are more waterlogging years and fewer drought years in high flow period in Yiwu. On the contrary, there are more drought years and fewer waterlogging years in low flow period in Yiwu. Precipitation increases obviously in the current or next year of E1 Nino events, while in reverse in the current or next year of La Nina events in Yiwu. The time of Meiyu season comes early and ends late in high flow period,average duration of Meiyu season is longer and average precipitation amount increases in high flow period, but it is just the contrary in low flow period. The beginning date of Meiyu season appears between 6th and 15th,June in Yiwu with maximum probability, however, the end date does not show the regularity. The end date of Meiyu season delays in the current or next year of E1 Nino events,and it comes ahead in the current or next year of La Nina events. This study would be helpful to artificial precipitation operation in the source area of reservoir during rainy season.