Interpretation of interannual winter temperature variations over southwestern Europe

A great part of winter temperature variability over southwestern Europe (SW E) shows a very low correlation with the North Atlantic or Arctic Oscillati on indices. The patterns of winter mean surface air temperature over SWE we re obtained from gridded and instrumental data. The first mode is highly co rrelated with the East Atlantic (EA) pattern and explains temperature varia tions of the same sign over the whole domain. The second mode, however, is correlated with the North Atlantic Oscillation (NAO) and shows a dipolar st ructure with significant negative values in northern Africa and the souther n Iberian Peninsula and positive values toward northern Europe. Thus the NA O only influences the meridional gradient of temperature over the area, and the second mode explains a significantly lower fraction of variance than t he first mode. Both modes of temperature variability depend on the stationa ry component of the sensible heat fluxes but cannot be explained through th e eddy sensible heat fluxes. It is well known that precipitation depends on the existence of baroclinic systems over the area. According to the result s in this paper, this does not hold for temperature. This explains the diff erent sensitivities of SWE precipitation and temperature to the North Atlan tic Oscillation.