Spatial and Temporal Variations in Precipitation and Aridity Index Series of Turkey

Abstract

Annual and seasonal precipitation series and annual aridity index series of Turkey were investigated with respect to spatial and temporal variations for the period 1930–1993. Analysis of normalized precipitation anomalies was also performed for the 1994–2000 period. Semi-arid and dry sub-humid climatic conditions are dominant over the continental interiors and continental Mediterranean region of Turkey. Normalized annual and winter precipitation series have tended to decrease over a considerable part of Turkey since the early 1970s. For the normalized annual and winter precipitation anomaly series, wet conditions generally occurred during the 1940s, 1960s, late 1970s, early 1980s and mid-late 1990s, whereas dry conditions generally dominated over the early-mid 1930s, early-mid 1970s, mid-late 1980s, early 1990s, and 1999/2000 in most of Turkey. Spring precipitation series generally indicated an upward trend from the mid 1940s to the late 1960s at many stations and to 1980s at some stations. This period was generally followed by a downward trend at many stations. Significant decreasing trends showed up in the annual precipitation series of 15 stations and in the winter precipitation series of 14 stations, mostly over the Mediterranean rainfall region. Summer rainfall series have tended to increase significantly at 7 stations. There has also been a general tendency from humid conditions of around the 1960s towards dry sub-humid climatic conditions in the aridity index values of many stations of Turkey. At some stations over the Aegean part of the Mediterranean region, there has been a significant change from humid conditions to dry sub-humid or semi-arid climatic conditions.