West African Monsoon influence on the summer Euro-Atlantic circulation

Abstract

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. Copyright © 2011 by the American Geophysical Union.