Meteorological drought, as an extreme event, takes place when monthly or yearly precipitation goes down below a threshold for a specific duration. Drought events are presented based on different drought characteristics, i.e., duration, magnitude, and severity. Meteorological drought characteristics change territorially and can be analyzed regionally. However, most of the meteorological drought analyses are commonly based on-site frequency analysis of univariate drought characteristics which does not fully describe the drought potential due to the existence of correlation between the drought characteristics and their regional properties. In this research, a regional bivariate analysis is proposed for meteorological drought analysis. Monthly precipitation depths of 41 meteorological stations in Khuzestan province, southwest of Iran, were collected and extended using time series analysis. The interevent volume method is used to pool the meteorological droughts at each meteorological station. Then, the pooled drought events characteristics (e.g., duration and severity) were used to specify the homogenous regions based on the L-moments analysis. The bivariate distribution of drought was estimated using the copulas for each homogeneous region. In this study, Khuzestan province was regionalized based on the bivariate risk of drought events. The proposed methodology is applicable to regional analysis of hydrological and agricultural droughts.
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Mirakbari et al. (2010) studied this question.