||Papadopoulos, V.; Josey, S.; Bartzoka, A.; Somot, S.; Ruiz, S.; Drakopoulou, P.;|
||Large scale atmospheric circulation favoring deep and intermediate water formation in the Mediterranean Sea|
||Journal of Climate (issn: 1520-0442)
Atmospheric circulation patterns that are conducive to extreme ocean heat loss are investigated at four sites of special interest in the Mediterranean Sea. The Gulf of Lions, the South Adriatic Sea, the Cretan Sea, and the Levantine Sea are all areas, where anomalously high winter heat loss may lead to deep or intermediate water formation. At each of the above sites, the atmospheric circulation during such events is derived by averaging the sea level pressure (SLP) fields during the lower decile of the winter time series of the net heat exchange. A relatively simple SLP pattern dominated by an anticyclone over north-west Europe with a weaker cyclone to the south-east is found to be associated with strong heat loss in the selected sites with minor variations in pattern structure depending on the site. The SLP composite pattern reflects the combined effect of different atmospheric modes of variability and we consider the impacts on heat loss of a number of these modes (NAO, EA, EAWR, SCAN), together with the NCP and MI indices. The extremes in heat loss are strongly connected with the intensity and the positions of the poles of these patterns which modulate, through the necessary SLP gradient and associated northerlies, the transfer of cold and dry air masses over the areas of dense water formation. Analysis of air-sea temperature difference, specific humidity and evaporation anomalies, indicates that the extremes of the net heat fluxes are primarily due to the latent and sensible heat flux components.
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