[1] 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 longand 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.

[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.

Time series of monthly sea-surface temperature (SST), air temperature (AT) and sea level pressure (SLP) were constructed from merged releases of the Comprehensive Ocean-Atmosphere Data Set (COADS). The time series were decomposed into seasonal and non-seasonal (short and long-term) components. The contribution of the seasonal cycle to the total variance of SST and AT exceeds 80% in the mid and in some high latitude locations and reaches its peak ( \ 95%) in the centres of subtropical gyres. In most cases, a combination of annual and semiannual harmonics accounts for more than 95% of the seasonal variability.Amplitudes of SST and AT annual cycles are highest near the western boundaries of the oceans; annual phases of SST and AT increase toward the eastern tropical oceans, revealing a southeastern propagation of the annual cycle over the Northern Hemisphere oceans. The annual cycle of AT leads that of SST by 1 -3 weeks. The largest phase differences are observed in the regions of western boundary currents in the North Pacific and the North Atlantic oceans. This is consistent with spatial patterns of integral air-sea heat fluxes. Annual phases of SST increase along the Gulf Stream and the Kuroshio Current. This points to the importance of signal transport by the major ocean currents.The lowest annual amplitudes of SLP are observed along the equator (0°-10°N) in both oceans. There are three distinct areas of high annual amplitudes of SLP in the North Pacific Ocean: Asian, Aleutian and Californian. Unlike the North Pacific, only one such area exists in the North Atlantic centred to the west of Iceland. A remarkable feature in the climate of the North Pacific is a maximum of semiannual SLP amplitudes, centred near 40°N and 170°W. It is also an absolute maximum in the entire Northern Hemisphere. Analysis of phases of harmonics of SLP seasonal cycle has revealed the trajectories of propagation of the annual and semiannual cycles.Analysis of semiannual to annual amplitudes ratio has revealed the regions of semiannual cycle dominance.

[1] Gridded monthly precipitation data for 1979-2006 from the Global Precipitation Climatology Project are used to investigate interannual summer precipitation variability over Europe and its links to regional atmospheric circulation and evaporation. The first empirical orthogonal function (EOF) mode of European precipitation, explaining 17.2%-22.8% of its total variance, is stable during the summer season and is associated with the North Atlantic Oscillation. The spatial-temporal structure of the second EOF mode is less stable and shows month-to-month variations during the summer season. This mode is linked to the Scandinavian teleconnection pattern. Analysis of links between leading EOF modes of regional precipitation and evaporation has revealed a significant link between precipitation and evaporation from the European land surface, thus, indicating an important role of the local processes in summertime precipitation variability over Europe. Weaker, but statistically significant links have been found for evaporation from the surface of the Mediterranean and Baltic Seas. Finally, in contrast to winter, no significant links have been revealed between European precipitation and evaporation in the North Atlantic during the summer season.Citation: Zveryaev, I. I., and R. P. Allan (2010), Summertime precipitation variability over Europe and its links to atmospheric dynamics and evaporation,

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