Frequency analyses of extreme precipitation events in Western Black Sea Basin (Turkey) based on climate change projections

The impacts of climate change on extreme precipitation events in the Western Black Sea Basin of Turkey were investigated by using the annual maxima (AM) and peaks over threshold (POT) methods. Daily precipitation data measured between 1971 and 2000 at nine meteorological stations and projected and dynamically downscaled precipitation data from the outputs of GFDL-ESM2M, HadGEM2-ES and MPI-ESM-MR global circulation models (GCMs) under Representative Concentration Pathway 4.5 (RCP4.5) and RCP8.5 scenarios were used to generate maximum daily rainfall intensity for 2, 5, 10, 20, 50, 100 and 500 year return periods. The outputs of the GCMs were corrected by a modified linear scaling bias correction method to offset the uncertainties of the GCMs before frequency analyses. The datasets were fitted to a generalized extreme value distribution and a generalized Pareto distribution for the AM and POT methods, respectively. Based on a statistical test a reliable goodness-of-fit was obtained. The results of frequency analyses of daily storms by using the GCM data, after bias correction, showed that by the end of the current century the magnitude of the storms will increase by 31.29% and 27.00% based on the AM and POT methods respectively under the RCP4.5 scenario and by 43.51% and 31.29% based on the AM and POT methods respectively under the RCP8.5 scenario. The magnitude of the 24 hr rainfall intensity calculated by the AM method was more than that of the POT method by 22% on average. For the whole basin (on average) the mean maximum daily rainfall intensity was found to be 33.45, 46.18, 57.24, 69.16, 87.68, 104.51 and 154.60 mm/day for the respective return periods.