West African Monsoon influence on the summer Euro-Atlantic circulation

Marco Gaetani (1) , Benjamin Pohl (2) , Hervé Douville (3) , Bernard Fontaine (2)

1 IBIMET - Istituto di Biometeorologia [Roma]
2 CRC - Centre de Recherches de Climatologie
3 CNRM - Centre national de recherches météorologiques

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-latitudes circulation. A strong monsoon is related to high-pressure anomalies over the Azores and positive NAO phases.

Domaines: Climatologie; Milieux et Changements globaux

Marco Gaetani, Benjamin Pohl, Hervé Douville, Bernard Fontaine. West African Monsoon influence on the summer Euro-Atlantic circulation. Geophysical Research Letters, 2011, 38, pp.L09705. ⟨10.1029/2011GL047150⟩. ⟨hal-00582619⟩