The Survey of Climate Change Impact on Drought Severity- Duration- Frequency Curves Using Copulas

Climate change has various effects on the quantity of rainfall and warming also is lead to increases in frequency and intensity of droughts by accelerating earth drying up and consequently. It is effective on the curves of severity- duration- frequency of drought (SDF). The purpose of this study is to evaluate the effects of climate change on SDF curves in the future in Qareh su basin located in the Golestan province. First, precipitation and temperature variables were generated using basin-areal average time series from years 1983-2012 and “CanESM2” model outputs as a general circulation model under the RCP 2.6, RCP 4.5 and RCP 8.5 scenarios and “SDSM” model as a statistical downscaling model over the period 2019-2048. Then SDF curves were derived from 3-month Reconnaissance Drought Index (RDI) and Copula approach and conditional return period in the base and future time periods. The results showed that monthly precipitation and temperature for the future time period under different scenarios are generally decreased and increased, respectively and the return period of a drought event with severity equal to 10 with respect to 6-month duration or less, is 5 years in the base period. The return periods of the same event under RCP 2.6, RCP 4.5 and RCP 8.5 are 21, 17 and 4 years, respectively.