基于SWAP及多维联合概率的广西气象干旱频率分析

Analysis of Meteorological Drought Frequency in Guangxi Based on SWAP and Multidimensional Joint Probability

伴随全球气候变暖与区域干旱灾害加剧,精细化识别干旱事件及分析其多变量特征频率,已成为区域干旱灾害风险管理的一个关键问题。基于广西1951—2015年日尺度、0.25°格点的标准化有效降水干旱指数(SWAP),采用旋转经验正交函数法(REOF)将广西进行干旱分区,提取干旱事件强度、面积、历时信息,通过拟合优选Copula函数,分析各分区干旱事件强度-面积-历时的二维、三维联合及同现频率特征。结果表明:广西干旱特征可分为桂西北、桂东、桂中、桂西南以及桂东等5个区域,各区域干旱强度与历时的最优边缘分布均为Lognormal、干旱面积的最优边缘分布为Generalized ExtremeValue;当区域干旱面积超过92%阈值时,面积的微小增大会导致干旱重现期急剧增大,而小于该阈值时,干旱频率对干旱强度的变化更敏感;桂中分区发生强度高、面积广且历时长的干旱事件频率最高。

With global warming and regional drought disasters aggravating,the multivariate characteristics and combined frequen⁃cy of drought events have become key problems in disaster risk management.This paper was based on the Standardized Weighted Average of Precipitation(SWAP)of 0.25°grid points and 1951-2015 in Guangxi,using Rotational Empirical Orthogonal Function method(REOF)to divide Guangxi into several drought regions,extracting drought intensity,area and duration,choosing the opti⁃mal Copula function and calculating the combination and co-occurrence recurrence period.The results show that:(1)Guangxi can be divided into five drought regions:northwest Guangxi,northeast Guangxi,middle Guangxi,southwest Guangxi and east Guangxi.Lognormal is the desirable edge distribution of intensity and area,and Generalized Extreme Value is the best edge dis⁃tribution of duration in all regions.(2)When the percentage of area beyond 92%,the small increase for the area will lead to the sharp increase of the recurrence period,but less than 92%,the recurrence period is more sensitive to the change of drought intensity.(3)The probability of drought with high intensity,wide area and long duration is the highest in middle Guangxi.