CR 71:139-153 (2016)  -  DOI: https://doi.org/10.3354/cr01433

ABSTRACT: The atmospheric circulation characteristics over Europe and the Mediterranean that favour extreme precipitation in Turkey are analysed. In total, 326 extreme precipitation events in Turkey are defined using a criterion involving the upper 1 and 5% percentiles of daily precipitation at 70 meteorological stations for the period 1979 to 2011. The 500 and 1000 hPa standard pressure level geopotential heights, 850 hPa level air temperature and relative humidity, 500 hPa level relative vorticity, 925 hPa level divergence and convective available potential energy obtained from the ERA-Interim data set are examined for the days before, during and after the events. A multivariate statistical approach including factor analysis and k-means cluster analysis is followed, and the events are classified into 7 clusters according to the corresponding atmospheric circulation characteristics. The results show that in most cases, a west to east movement of strong upper air disturbances (mainly troughs with strong gradient toward or over Turkey) and low-pressure systems over the Eastern Mediterranean Basin, particularly south of Turkey, play a significant role for the occurrence of extreme precipitation events. The details referring to the areas of low level convergence, positive vorticity advection, high relative humidity and instability play a dominant role in the spatial and temporal distribution of the events.

KEY WORDS: Turkey · Mediterranean · Extreme precipitation · Atmospheric circulation · Factor analysis · k-means cluster analysis