Climate zones of Turkey are redefined by using the mathematical methodology of cluster analysis. Data from 113 climate stations for temperatures (mean, maximum and minimum) and total precipitation from 1951 to 1998 are used after standardizing with zero mean and unit variance, to confirm that all variables are weighted equally in the cluster analysis. Hierarchical cluster analysis is chosen to perform the regionalization. Five different techniques were applied initially to decide the most suitable method for the region. Stability of the clusters is also tested. It is decided that Ward's method is the most likely to yield acceptable results in this particular case, as is often the case in climatological research. Seven different climate zones are found, as in conventional climate zones, but with considerable differences at the boundaries.

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ABSTRACT:In the present study, annual, wet and dry seasons precipitation records for the period 1961-2008 from 271 stations in Turkey were analysed using the rotated empirical orthogonal function (REOF), the Mann-Kendall trend test and the continuous wavelet transform (WT) method. Additionally, relationships between time variability of the significant spatial patterns and North Atlantic Oscillation (NAO), Arctic Oscillation (AO), and North-Sea Caspian Pattern (NCP) are examined. The REOF method was used to analyse the annual, dry, and wet season variability of precipitation patterns over Turkey. The Mann-Kendall method was used to detect the temporal trend of the rotated principal components (RPCs) time series, and the continuous wavelet method was used to explore the periodicity of precipitation changes. Continuous WT results indicate that the significant 3-4 year, 6-10 year, and 12-16 year bands are the major period components. Precipitation in Turkey is uneven in space and time, and its complex temporal structure and spatial variations are different in each dry and wet season. The Mann-Kendall test results show that decreasing annual precipitation is the dominating trend throughout Anatolia, including west, and southwest sections. Increasing annual precipitation can be observed in only northeast Black Sea region of Turkey. Decreasing wet/dry season precipitation that we observe throughout the country, except northeast coasts and eastern parts of Turkey, is expected to have a strong impact on the economic livelihood of the region, especially on agricultural production, drinking water supply, and hydroelectricity production.

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