基于copula函数的区域干旱分析方法

Regional drought analysis approach based on copula function

提出不同网格干旱等级影响下的区域干旱指数。采用copula函数,建立了区域干旱历时和干旱强度的联合分布,计算联合分布的重现期,并对实际重现期作区间估计。所提出的区域干旱指数能够反映研究区域内发生干旱的严重程度和该区内不同干旱等级所影响面积的大小,且联合分布同时考虑了干旱历时和干旱强度,更全面地反映区域的干旱状况。重庆市2006年干旱实证分析表明,区域干旱指数能够较好地描述本次干旱的发生发展过程,并计算出联合分布的重现期为118年。

A regional drought index is proposed,which can take into account sub-grid variations in drought severity as well as in drought disaster area.The Copular function is used to establish the joint distribution of drought duration and severity over a region.The return period of the joint distribution can be used to study the characteristic of historical drought events and estimate the current drought return period.The index is applied to study the 2006 drought event in Chongqing,southwest of China.The result reveals that the drought development can be adequately reconstructed using the index.The drought characteristics,such as intensity and duration,can also be well quantified by the index.The calculated return period of joint distribution for the 2006 event is 118 years,which reflects the observed reality from the drought disaster.The result demonstrates the importance of considering the sub-grid drought variations and the significance of using the joint distribution in the establishment of the index.The index can thus have the potential of representing the severity of a regional drought in a comprehensive manner.