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    Changes in precipitation and river flow in northeast Turkey: Associations with the North Atlantic Oscillation
    (2010) Sariş, Faize; Hannah, David M.; Eastwood, Warren J.
    This paper explores the relationships between the North Atlantic Oscillation (NAO) index and precipitation and river flow over northeast Turkey. Precipitation totals and maximum, mean and minimum river flow are analysed at the seasonal scale for 12 and 10 stations, respectively. Pearson's and Mann-Kendall correlation tests are applied to assess relationships between the NAO index and precipitation and river flow metrics, and to detect trends in time-series. Autumn precipitation totals display significant increasing trends, especially for coastal stations, while inland stations show significant increasing trends for spring precipitation. Minimum and maximum river flow decreases significantly for spring and summer. This tendency implies varying conditions towards a drier regime. Seasonal precipitation patterns show a negative association with the NAO for December-January-February (DJF), March-April-May (MAM) and September-October-November (SON) for some stations. Positive associations between the NAO and winter-extended winter (December-March) river flows are detected for some stations in northeast Turkey. Copyright © 2010 IAHS Press.
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    Spatial variability of precipitation regimes over Turkey
    (Taylor & Francis Ltd, 2010) Saris, Faize; Hannah, David M.; Eastwood, Warren J.
    Turkish annual precipitation regimes are analysed to provide a large-scale perspective and redefine precipitation regions. Monthly total precipitation data are employed for 107 stations (1963-2002). Precipitation regime shape (seasonality) and magnitude (size) are classified using a novel multivariate methodology. Six shape and five magnitude classes are identified, which exhibit clear spatial structure. A composite (shape and magnitude) regime classification reveals dominant controls on spatial variability of precipitation. Intra-annual timing and magnitude of precipitation is highly variable due to seasonal shifts in Polar and sub-Tropical zones and physiographic factors. Nonetheless, the classification methodology is shown to be a powerful tool that identifies physically-interpretable precipitation regions: (1) coastal regimes for Marmara, coastal Aegean, Mediterranean and Black Sea; (2) transitional regimes in continental Aegean and Southeast Anatolia; and (3) inland regimes across Central and Eastern Anatolia. This research has practical implications for understanding water resources, which are under ever growing pressure in Turkey.