An Intercomparison of Simulated Rainfall and Evapotranspiration Associated with a Mesoscale Convective System over West Africa

Guichard, Francoise; Asencio, Nicole; Redelspurger, Jean-Luc; Lafore, Jean-Philippe; Nuret, Mathieu; Boone, Aaron; Decharme, Bertrand; Peugeot, Christophe; Bock, Olivier; Cui, Xuefeng; Morse, Andrew; Garvert, Matthew; Gaertner, Miguel Angel; Lamptey, Benjamin; Orlandi, Emiliano; Sander, Julia; Jones, Sarah C.; Fierli, Federico; Balsamo, Gianpaolo; de Rosnay, Patricia; Harris, Philip; Berges, J.-C.. 2010 An Intercomparison of Simulated Rainfall and Evapotranspiration Associated with a Mesoscale Convective System over West Africa. Weather and Forecasting, 25 (1). 37-60. 10.1175/2009WAF2222250.1

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Abstract/Summary

An evaluation of precipitation and evapotranspiration simulated by mesoscale models is carried out within the African Monsoon Multidisciplinary Analysis (AMMA) program. Six models performed simulations of a mesoscale convective system (MCS) observed to cross part of West Africa in August 2005. Initial and boundary conditions are found to significantly control the locations of rainfall at synoptic scales as simulated with either mesoscale or global models. When initialized and forced at their boundaries by the same analysis, all models forecast a westward-moving rainfall structure, as observed by satellite products. However, rainfall is also forecast at other locations where none was observed, and the nighttime northward propagation of rainfall is not well reproduced. There is a wide spread in the rainfall rates across simulations, but also among satellite products. The range of simulated meridional fluctuations of evapotranspiration (E) appears reasonable, but E displays an overly strong zonal symmetry. Offline land surface modeling and surface energy budget considerations show that errors in the simulated E are not simply related to errors in the surface evaporative fraction, and involve the significant impact of cloud cover on the incoming surface shortwave flux. The use of higher horizontal resolution (a few km) enhances the variability of precipitation, evapotranspiration, and precipitable water (PW) at the mesoscale. It also leads to a weakening of the daytime precipitation, less evapotranspiration, and smaller PW amounts. The simulated MCS propagates farther northward and somewhat faster within an overall drier atmosphere. These changes are associated with a strengthening of the links between PW and precipitation.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1175/2009WAF2222250.1
Programmes:	CEH Programmes pre-2009 publications > Biogeochemistry > CC01B Land-surface Feedbacks in the Climate System > CC01.8 Land-surface feedbacks through energy and water cycles CEH Programmes pre-2009 publications > Biogeochemistry > CC01B Land-surface Feedbacks in the Climate System > CC01.6 Development of the Joint Unified Land Exchange Scheme (JULES) land-surface model CEH Topics & Objectives 2009 - 2012 > Biogeochemistry
UKCEH and CEH Sections/Science Areas:	Harding (to July 2011)
ISSN:	0882-8156
Additional Keywords:	West Africa, AMMA, monsoon, convection, evaporation
NORA Subject Terms:	Meteorology and Climatology Hydrology Atmospheric Sciences
Date made live:	20 Apr 2010 11:51 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/5119

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