Comparison of the Calculated Drought Return Periods Using Tri-variate and Bivariate Copula Functions Under Climate Change Condition

Concerning the various effects of climate change on intensifying extreme weather phenomena all around the world, studying its possible consequences in the following years has attracted the attention of researchers. As the drought characteristics identified by drought indices are highly significant in investigating the possible future drought, the Copula function is employed in many studies. In this study, the two- and three-variable Copula functions were employed for calculating the return period of drought events for the historical, the near future, and the far future periods. In this paper, bivariate and trivariate of Copula functions were applied to evaluate the return periods of the drought in the historical period and the two near and near future periods. Moreover, the results of considering bivariate and trivariate of Copula functions were compared separately with the results of the calculated return periods for each of the drought characteristics; accordingly, the role of each drought characteristics was considered. The most severe historical drought was selected as the benchmark, and the drought-zoning map for the GCM models was drawn. The results showed that severe droughts could be experienced, especially in the upper area of the basin where the primary water resource is located. In addition, the nature of the drought duration plays a decisive role in calculating the return periods of drought events.

Automated summary

Researchers are focusing on the various effects of climate change on intensifying extreme weather phenomena globally, especially studying the possible consequences for coming years. The use of Copula functions is significant in analyzing drought characteristics and calculating return periods for historical, near future, and far future drought events. Results show that drought duration plays a crucial role in determining the return periods of drought events, especially in severe drought-prone areas like the upper basin where primary water resources are located.