Decadal precipitation variability over Europe and its relation with surface atmospheric circulation and sea surface temperature

The relationships between decadal (>5-year period) observed winter precipitation (PP) variability over Europe and atmospheric circulation and sea surface temperature (SST) during the period 1950-1995 are investigated. More than 48% of the decadal precipitation variability is described by two modes: a meridional dipolar pattern (high PP over northern Europe and low over southern Europe, the Mediterranean and most of central Europe) explaining about 32% of the variance, and an alternating pattern in latitude over Europe (high in central Europe and low in far north-western Europe and the Mediterranean) explaining about 16% of the variance. The first mode is strongly related to the North Atlantic oscillation. A canonical correlation analysis between regional precipitation and sea-level pressure fields shows that a PP pattern similar to the first decadal PP mode is associated with a north-westerly circulation anomaly pattern while a PP pattern similar to the second decadal PP mode is associated with a monopolar circulation anomaly pattern over most parts of Europe. The correlation map between the time series of expansion coefficients of the first PP mode and sea surface temperature emphasizes a global pattern which resembles the linear trend coefficients pattern of SST for the analysed period. The second PP mode is associated with an SST anomaly pattern similar to that of the SST anomalies characterizing 'decadal El Ni (n) over tildeo Southern Oscillation' SST pattern. Composite maps of global 500 mb geopotential height based on the time series of expansion coefficients of PP modes emphasize global patterns compatible with SST patterns. After removing the linear trend from the data, the first PP pattern remains almost unchanged but it emphasizes mainly regional connections. The second spatial pattern of the second PP mode and its connections are not affected significantly by removing the trend.