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AGU: Geophysical Research Letters

 

Keywords

  • NAO
  • West African monsoon
  • climate modeling
  • climate variability
  • grid-point nudging
  • tropical-extratropical interaction

Index Terms

  • Global Change: Climate dynamics
  • Atmospheric Processes: General circulation
  • Atmospheric Processes: Global climate models
  • Geographic Location: Africa
  • Geographic Location: Atlantic Ocean

Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 38, L09705, 5 PP., 2011
doi:10.1029/2011GL047150

West African Monsoon influence on the summer Euro-Atlantic circulation

Key Points
  • The role of the WAM in driving the Euro-Atlantic circulation is highlighted
  • Strong WAM is related to high-pressure anomalies over Azores and positive NAO
  • The nudging replaces the NAO centers of action close to their observed locations

Marco Gaetani

CETEMPS, Università dell'Aquila, L'Aquila, Italy

IBIMET, CNR, Rome, Italy

Benjamin Pohl

CRC, CNRS, Université de Bourgogne, Dijon, France

Hervé Douville

CNRM-GAME, Météo-France, CNRS, Toulouse, France

Bernard Fontaine

CRC, CNRS, Université de Bourgogne, Dijon, France

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.

Received 16 February 2011; accepted 1 April 2011; published 13 May 2011.

Citation: Gaetani, M., B. Pohl, H. Douville, and B. Fontaine (2011), West African Monsoon influence on the summer Euro-Atlantic circulation, Geophys. Res. Lett., 38, L09705, doi:10.1029/2011GL047150.

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