Long-term spatiotemporal trend analysis of precipitation and temperature over Turkey

Abstract

Monthly precipitation and temperature data for Turkey were obtained from the Climate Research Unit Time Series (CRU TS V3.23) dataset (1901-2014) and analysed. The records of 81 grids, each located in a province, were converted into annual and seasonal data. The Mann-Kendall test was used to determine trend significance. The Theil-Sen slope estimator was used for estimating the magnitude of the trend. The Pettitt-Mann-Whitney test was used on the annual data series to identify the most probable change year' for precipitation and temperature. The spatial pattern of the trend was analysed using a geographical information system environment. The results showed that the annual areal precipitation over the whole of Turkey is not significantly increasing with a magnitude of 0.11 mm year(-1), but the annual areal temperature is increasing significantly with a magnitude of 0.88 degrees C century(-1). The grid analysis indicated that annual precipitation is decreasing in the southeastern Anatolia and Mediterranean regions and increasing in the Marmara and Black Sea regions, whilst other regions have no specific pattern. Although a trend is present in most of the grids, insignificance is dominant. Annual precipitation has no dominant change year with 1969 being the most probable. Seasonal precipitation has increasing and decreasing trends in the same regions that also show such trends in annual precipitation. Annual temperature has a significant, increasing trend in all regions. 1993 was found as the most probable change year. Seasonal temperature showed an increasing trend in all regions. The highest increasing trend for temperature was found in the summer.