Spatiotemporal variability of precipitation total series over Turkey

Long‐term changes and trends in the series of monthly, seasonal and annual precipitation totals of 97 stations in Turkey were analysed by considering their spatial and temporal characteristics. Secular trends in precipitation series were examined with the Mann–Kendall rank correlation test for the general period 1930–2002, whereas spatial variabilities of, and relationships between, the precipitation series at 86 of these stations were investigated by the principal component analysis (PCA) for the period 1953–2002 when the length of data is at its best for the stations subjected to the PCA. Major findings of the paper can be summarized as follows: (1) First principal component (PC1) generally describes climatology of the precipitation totals in Turkey that is closely governed by the large‐scale and/or synoptic scale atmospheric features (i.e. surface and upper air pressure and wind systems). (2) In winter, it is very likely that the greater PC1 loadings over the western and south‐western parts of Turkey characterized mainly with the Mediterranean rainfall regimes indicate influence of the large‐scale atmospheric circulation and associated weather patterns. However, smaller PC1 loadings over the north‐eastern and eastern parts of Turkey are very likely related to the influence of the northerly mid‐latitude cyclones, and the northerly and easterly circulations linked with the Eastern Europe and the Siberian originated high pressures on spatial variations of winter precipitation. (3) As for the long‐term temporal variability, it was detected that there is an apparent decreasing trend in the winter precipitation totals of Turkey, whereas a general increasing trend is dominant in the precipitation totals of spring, summer and autumn seasons. (4) Observed decreasing trends are the strongest over the Mediterranean and the Mediterranean Transition rainfall regime regions. (5) Strong decreasing trends are also mostly found in winter months of the year, while apparent increasing trends show up at some stations in the months of April, August and October. Copyright © 2008 Royal Meteorological Society