West African Monsoon influence on the summer Euro-Atlantic circulation
Gaetani, M. ; Pohl, B. ; Douville, Hervé ; Fontaine, B.
The West African Monsoon (WAM) influence on the interannual variability of the summer atmospheric circulation over North Atlantic and Europe is investigated over the period 1971-2000. A set of sensitivity experiments performed through the Arpege-Climat Atmospheric General Circulation Model is analyzed, using the so-called grid-point nudging technique, where the simulated atmospheric fields in the WAM region are relaxed towards the ERA40 reanalysis. Observations confirm that a sizable part of the Euro-Atlantic circulation variability is related to the WAM, with anomalies of reinforced convection in the Sudan-Sahel region associated with positive North Atlantic Oscillation (NAO) phases and subsidence over eastern Mediterranean. The nudged simulations highlights the role of the WAM in driving the mid-latitude circulation. A strong monsoon is related to high-pressure anomalies over the Azores and positive NAO phases.
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