“…Copulas are often used for bivariate frequency analysis of hydrological extremes including droughts (Shiau, ; Chen et al , ; Masud et al , ; Xu et al , ; Hao et al , ). For an n ‐dimensional random vector X = ( x 1 , x 2 , x 3 , …, x n ) with continuous marginal CDFs F 1 ( x 1 ), F 2 ( x 2 ), F 3 ( x 3 ), …, F n ( x n ) according to Sklar's theorem (Sklar, ), the multivariate CDF of X can be expressed as: where C is the copula function that represents dependences between random variables and marginal cumulative distributions.…”