Agricultural sector of Fars Province plays a substantial role in ensuring food security in Iran. Unfortunately, in recent decade wide areas of the province have been affected by drought phenomenon. Due to significant correlation between drought characteristics and the existence of ungagged areas, in this research, a regional bivariate analysis is recruited for meteorological drought. The aims of this analysis are to shed the light upon the effects of interdependence drought characteristics on frequency of occurrence and return period, in addition, improve the results comparing to local frequency analysis in Fars Province. Drought events are analyzed via the Standardized Precipitation Index and run theory. For regional frequency analysis, the index drought procedure which is coupled with the L-moments method is employed and the bivariate distribution of drought is estimated through the copulas for a homogeneous region. The results present that the marginal distributions for duration and severity variables are exponential and 2-parameter gamma, respectively. The Gumbel copula is the most suitable copula for representing joint distribution of drought characteristics. Comparing univariate and multivariate return periods for different non-dimensional severity and durations having identical marginal cumulative distribution function amounts indicate their values are relatively close up to 20 year. However, a significant discrepancy has been revealed when univariate return periods are 50 and 100 year which have a critical role in risk analysis and water resources management. To sum up, drought severity with duration greater than 6 month was estimated in different return periods for all of stations and it is observed that drought severity in northwest is greater than the southwest in under-studied region.

中文翻译：

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使用 Copula 函数进行区域干旱频率分析（案例研究：伊朗法尔斯省半干旱气候的一部分）

法尔斯省的农业部门在确保伊朗的粮食安全方面发挥着重要作用。不幸的是，近十年来全省大面积地区都受到干旱现象的影响。由于干旱特征与未加盖地区存在显着相关性，本研究对气象干旱进行区域双变量分析。该分析的目的是阐明相互依赖的干旱特征对发生频率和重现期的影响，此外，与法尔斯省当地频率分析相比，改进结果。通过标准化降水指数和运行理论分析干旱事件。对于区域频率分析，采用与 L 矩方法相结合的指数干旱程序，并通过同质区域的 copula 估计干旱的双变量分布。结果表明，持续时间和严重性变量的边际分布分别是指数和 2 参数 gamma。Gumbel copula 是最适合表示干旱特征联合分布的 copula。比较具有相同边际累积分布函数量的不同无量纲严重性和持续时间的单变量和多变量返回期表明它们的值相对接近 20 年。然而，当单变量回报期为 50 年和 100 年时，显着差异已被揭示，这在风险分析和水资源管理中具有关键作用。总结，