A determination of season shifting across Turkey in the period 1965–2020

Abstract

AbstractSignificant changes in the onset, length and thermal characteristics of seasons have been reported all over the globe in recent decades; however, the spatiotemporal changes of seasonal characteristics in Turkey have received little attention in relation to seasons delineation. In this study, the changes in the characteristics of Turkish seasons have been examined from 1965 to 2020 by considering the daily average temperature data obtained from 65 meteorological stations. A nonstatic definition of season onset was used to delineate the seasons. The study also presents the response of seasons timing and thermal characteristics affected by climate change. All over Turkey, the trend rate for beginning of summer was determined to be 2.1 days·decade−1 from 1965 to 2020, while the beginning of winter has shifted forward at many stations in southeastern Anatolia. All the seasons have experienced increases in average temperatures. The maximum increase was in summer seasons and occurred at up to a rate of 0.7°C·decade−1. There has been almost no change in winter temperatures over the Mediterranean region. Eastern Marmara with the western and middle Black Sea regions experienced an extension of spring as well as a shortening of the autumn season. It was noted that the change in the beginning of summer occurred all over the country. However, the extension of spring and shortening of the autumn season was mainly limited to the western Black Sea regions. The seasons, defined by considering climate change and variability, showed significant trends for length, average temperature and their onset. To the best of the author's knowledge, the delineation of seasons using a dynamic approach is the first attempt of its kind in this study area.