Drought Trends in Türkiye Under Global Warming Conditions

Abstract

The methods used in monitoring the increasing drought are vitally significant. In order to determine and monitor drought, many scientific studies have been carried out in our country, especially using the standardized precipitation index (SPI). However, due to increasing temperatures and evaporation, there is a need for studies showing the spatio-temporal change of drought at the country scale according to the standardized precipitation evapotranspiration index (SPEI), which also takes evaporation into account. The change in drought indices according to different evapotranspiration methods is also of interest. In this study, spatio-temporal comparison of drought trend and trend magnitude at 1, 6 and 12-month time scales according to SPI and SPEI indices was aimed by using meteorological observation data of 81 meteorological stations in Türkiye between 1980-2019. FAO-56 Penman-Monteith (PM) and Hargreaves (HG) reference evapotranspiration methods were used to calculate the SPEI index. Temporal trend analyses were conducted by Modified Mann-Kendall method and drought slope magnitude analyses by Sen’s Slope Estimator and spatial analyses by IDW method. According to the SPI index trend analysis for a 1, 6 and 12- month time scale, especially the drought in the Black Sea, the Marmara and Aegean Regions of Türkiye showed a significant downward trend while a significant upward trend of drought was seen in the other regions. The findings revealed that the humid periods were more prevailing than the dry periods in these areas that have downward drought trend. Unlike the SPI, the trend analysis of SPEIPM and SPEIHG index, downward trend of drought was only encountered in the coastal provinces of the Aegean region, the Central Black Sea, and the West Marmara Region. A significant upward trend of drought was observed in the majority of Central Anatolia, Eastern Anatolia, and Southeastern Anatolia Regions according to the SPEIPM and SPEIHG index.