Seasonality in precipitation variability over Europe

Abstract

A gridded monthly and pentad precipitation for 1979-2001 from the Climate Prediction Center Merged Analysis of Precipitation (CMAP) data set and terrestrial monthly gauge-based precipitation for 1958-1998 from the Climatic Research Unit, University of East Anglia (CRU), data set are used to investigate seasonality in the long-and short-term precipitation variability over Europe. Prominent seasonal differences are detected both in precipitation climatologies and in characteristics of precipitation variability. It is shown that over western Europe the summer precipitation climatology and its year-to-year variability (expressed by standard deviations) are lower than those of the winter precipitation. Major seasonal differences are found over central eastern Europe. In this region the summer precipitation climatology and magnitudes of its interannual variability exceed respective winter characteristics by a factor of 2-3.5. Similar relationships are found for the summer and winter magnitudes of intraseasonal fluctuations of precipitation. The first empirical orthogonal function (EOF) modes of both summer and winter seasonal mean precipitation over Europe are associated with the North Atlantic Oscillation (NAO). However, they explain very different (42% for winter and 25% for summer) fractions of total precipitation variability and form principally different spatial patterns. Temporal behavior of the respective principal components is also essentially different. The first EOF mode of the winter magnitudes of intraseasonal precipitation fluctuations is also associated with the NAO. The second EOF mode of the winter precipitation is linked to the East Atlantic teleconnection pattern. However, the respective mode in the magnitudes of intraseasonal fluctuations was not detected. The second EOF mode of the summer precipitation is associated with the 500 hPa heights pattern, which is characterized by four anomaly centers. Two major centers of opposite polarity are located over western Europe and Scandinavia-northeastern European Russia. Copyright 2004 by the American Geophysical Union.