Seasonally varying modes in long‐term variability of European precipitation during the 20th century

Abstract

[1] A gridded monthly terrestrial gauge-based precipitation for 1901-2000 from the Climatic Research Unit, University of East Anglia, set is used to investigate leading seasonal modes in the long-term precipitation variability over Europe and their links to atmospheric circulation. Performed empirical orthogonal function (EOF) analysis has shown that the leading modes of precipitation variability over Europe are clearly seasondependent. The character of the links between regional precipitation and atmospheric circulation also features essential seasonality. The first EOF modes of the winter, spring, and summer seasonal mean precipitation over Europe are associated with the North Atlantic Oscillation (NAO). However, because the summer NAO differs significantly from the winter and spring NAO, the first EOF mode of the summer precipitation has a spatialtemporal structure which is principally different from those of the winter and spring seasons. The first EOF mode of the fall precipitation is not associated with the NAO. This mode demonstrates a strong link to the Scandinavian teleconnection pattern. The second EOF modes of the winter and fall precipitation are linked to the east Atlantic and the NAO teleconnection patterns, respectively. Analysis of running correlations between the principal components of the leading EOF modes of precipitation and the NAO index has revealed nonstationarity of the links between European precipitation and the NAO. Moreover, there is evident seasonality in the character of the long-term changes of the above links.

Summertime precipitation variability over Europe and its links to atmospheric dynamics and evaporation

“…edu. Since observational data over land are rather scarce, as a complementary data source on evaporation over the land surface, we used data from the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) Reanalysis for 1979-2006[Kalnay et al, 1996. These data are diagnostic outputs from 6-hourly forecasts produced by a numerical weather prediction model in data assimilation mode.…”

“…[5] We employed monthly mean global precipitation data (2.5°× 2.5°latitude-longitude grid) from the Version-2 of the GPCP data set for 1979-2006[Huffman et al, 1997Adler et al, 2003]. The GPCP data set represents a combination of gauge observations and satellite estimates.…”

“…We also examine stability of the links between the leading modes of regional precipitation and regimes of atmospheric circulation during summer season. Note, our recent analysis [Zveryaev, 2006[Zveryaev, , 2009 revealed significant interdecadal changes in such links. Furthermore, we investigate connection between European precipitation and evaporation from the surface of the North Atlantic Ocean, the Mediterranean and Baltic seas, and from the European land surface.…”

“…While our recent studies [Zveryaev, 2004;2006] highlighted seasonal differences in precipitation variability over Europe and were based on analysis of seasonal mean precipitation, the present study examines summer season evolution of the leading modes of regional precipitation. In other words, we address the question of how stable are the leading modes of summer season precipitation, a highly variable (both in time and space) climate parameter.…”

“…[3] In contrast to winter, when European precipitation variability is mostly driven by the North Atlantic Oscillation (NAO) [e.g., Hurrell, 1995;Qian et al, 2000;Zveryaev, 2006], mechanisms driving interannual variability of regional precipitation during summer are more complex and are not well understood. In summer, when the role of atmospheric moisture advection in precipitation variability is diminished, the role of the local land surface processes increases [Trenberth, 1999].…”