松花江干流洪水与1998年松嫩大水分析--发生规律及成因

松花江干流洪水的发生有24年和3～4年变化周期.洪水出现有明显的阶段性,在上世纪可分为4段1911-1914;1930-1940;1954-1958;1984-1998年.随着时间的推移,洪水发生频次明显增加.分析得出,嫩江流域及第二松花江和拉林河流域7,8月的过量降水是造成洪水发生的直接原因.还分析了造成洪水的高空500hPa环流背景,7,8月西藏高原至北美阿拉斯加距平场分布为“ - -“流型,鄂霍次克海为阻塞高压,东北区为低压槽控制.在大水年春季,阿留申低槽加深,并向西延伸,乌拉尔高压形成并东移加强.1998年松嫩大水的发生基本符合上述规律和环流原因.

Analysis of floods in main stream of Songhua River and Song-Nen Valley flood in 1998:cause and regularily of occurrence

Occurrence of flood in the Songhua River has 24 Years and 3~4 Years change Periods respectively and there were four occurrence intervals in 20th century as 1911-1914,1930-1940,1954-1958 and 1984-1998.The frequency of the flood has a increasing trend in recent years.Excessive precipitation is a direct cause to lead flood.Relevant 500hPa circulation background in upper air was analyzed.The distribution of anomaly field from Tibet Plateau to Alaska in North America in July and August is "+-+-" type.Okhotsk Ocean is blacking high,northeastern China is controlled by low trough.In the spring of flood years,the low trough in Aleutian deepens and extends to west,the high in Ural forms,strengthens and moves to east.The occurrence of the flood happened in Song-Nen Valley in 1998 coincided with the cause and regularity analyzed above.