A downscaling application for local meteorological variables of Eastern Black Sea Basin and scenario based predictions

Abstract

Climate change has become one of the most important problems discussed around the world due to its environmental, economic and social impacts. In order to determine the magnitude of the impact of climate change and possible adaptation studies, it is necessary to determine the changes in the future periods of temperature and precipitation being the most important variables of the climate. For this purpose, scenario outputs of general circulation models (GCM) with coarse spatial resolution are used. The low resolution of these outputs limits their direct use in determining the effects of climate change on a local scale. Therefore, GCM outputs should be downscaled into finer scale. The aim of this study is to determine the possible effects of climate change on precipitation and temperature values of Eastern Black Sea Basin (EBSB), which is one of the most important hydrological basin in Turkey. For this purpose, the coarse resolution outputs of the GFDL-ESM2M model under RCP4.5 and RCP8.5 scenarios were reduced to local scale using the multivariate adaptive regression splines (MARS) and classical regression analysis (CRA) methods. Various performance statistics were used to compare the downscaling capabilities of MARS and CRA based models, and the method with the highest performance was determined according to these statistics. Within the scope of the study, the monthly average temperature and total precipitation values for the next period (2021-2050, 2051-2080, 2081-2100) of 12 meteorology stations located in and around the basin were produced by using MARS-based models that give the best performance values. Mann-Kendall trend analysis was also applied to the scenario data obtained. According to the results, it is expected that the temperature values in the southern part of the basin with terrestrial climate characteristics (Bayburt, Gumushane, Susehri ve Sebinkarahisar stations) will increase by an average of 1 degrees C according to the RCP4.5 scenario and 1.5 degrees C according to the RCP8.5 scenario in the period 2021-2050. In addition, temperature increases of up to 2.5 degrees C are foreseen on the coastline of the basin where the Pazar, Rize and Hopa stations are located. According to the outputs of both scenarios, is expected in long-term precipitation average values in almost all of the basin. In the periods of 2051-2080 and 2081-2100, it is foreseen that the increases and decreases in temperature and precipitation values will be more than the 2021-2050 period. According to the results of the trend analysis, the RCP4.5 scenario for temperature and precipitation, no trend is expected in the future, while according to the RCP8.5 scenario, an increase trend for temperature and a decrease trend for precipitation have been determined.