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The impact of deep convection on the West African summer monsoon climate: a regional climate model sensitivity study
Author(s) -
Sylla M. B.,
Giorgi F.,
Ruti P. M.,
Calmanti S.,
Dell'Aquila A.
Publication year - 2011
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.853
Subject(s) - climatology , orographic lift , african easterly jet , convection , intertropical convergence zone , tropical wave , monsoon , climate model , baroclinity , geology , deep convection , potential vorticity , atmospheric sciences , climate change , meteorology , vorticity , geography , vortex , tropical cyclone , oceanography , precipitation
The role of the representation of deep convection on key elements of the West African summer monsoon climate is addressed using the Regional Climate Model RegCM3. Two simulations in which a scheme of deep convection is activated and then turned off are performed and intercompared. Results show that the presence of deep convective heating along the intertropical convergence zone sustains increased lower‐level baroclinicity favoring intensification of the jet core and leading to a more realistic African easterly jet. In addition, although the isentropic potential vorticity (IPV) is lower when the convection scheme is switched off, African easterly waves (AEWs) are still generated and propagate westwards but they dissipate around the west coast. Substantial differences between the two simulations occur mainly at the 6‐ to 9‐day time‐scale over land, when much weaker activity is simulated in the absence of convection. This indicates that orographic friction and low‐level large‐scale moisture convergence, generating high values of latent heat and IPV, may play the dominant role in the genesis and growth of AEWs and that deep convection acts to strengthen the overall wave activity and to favor their west coast development. Copyright © 2011 Royal Meteorological Society