广西前汛期旱涝特征及成因分析

Characteristic of Flood and Draught in Pre-flood Period of Guangxi and the Causes Analysis

利用 EOF分解和 Z指数对广西前汛期 (4～ 6月 )降水进行型态分布及旱涝等级的划分 ,研究旱涝的空间分布、年际变化及年代际变化 ,并对旱涝成因进行了分析。结果表明 :广西前汛期降水的一致性较好 ;6 0年代和 90年代为旱涝多发年代 ,70年代以涝为主要特征 ,80年代以旱为主要特征。影响广西前汛期降水的环流因子主要有中高纬环流经向度、北半球极涡、印缅槽及副热带高压 ;

Through the EOF analysis method and Z index,kenel distribution of precipitation as well as flood and draught level in the pre flood period(April^June) are graded with a view to study the spatial distribution,annual changes and changes in decades of flood and draught,and an analysis for the causes of flood and draught is also made.The results of study and analysis show that:Precipitation of Guangxi in the pre flood period has a good conformity;the 1960s and 1990s are featured by flood and draught,and the 1970s by flood,the 1980s by draught.The circumfluent factors influencing the precipitation of Guangxi in pre flood period are warp direction of circulating current in mid and high latitude,polar vortex in the Northern Hemisphere,Indo Burma trough and subtropical high atmospheric pressure;the Pacific Ocean area in the mid and low latitude also has an obvious effect on the precipitation of Guangxi in pre flood period.