Sensitivity of a modelled life cycle of a mesoscale convective system to soil conditions over West Africa

Cloud-resolving real-case simulations initialized with European Centre for Medium-ranee Weather Forecasts (ECMWF) analysis data- were performed to investigate the sensitivity of a mesoscale convective system (MCS) to soil properties Four scenarios were investigated original ECMWF soil moisture (001). ECMWF soil MOISLUIC reduced by 35% (CTRL) which better fits with the satellite observations, homogeneous soil type and soil moistme (HOM). and homogeneous soil type with a north south oriented dile brand of two degrees width (BAND) Initiation of convection was observed in all experiments The initiation area was charactensed by very low convective inhibition (CIN) and hieh convective available potential energy (CAPE) The simulations showed some evidence that Convection was in in the vicinity of orogiaphy and along soil moisture inhomoeenemes. Except for the MOI MCSs developed in all expemnents In CTRL. a weakenmg of the system was observed when approaching an area with reduced total water content and enhanced CI N. In BAND. convection developed almost simultaneously in the original in area and inside thc dry band. Miele convcieence, generated by thermally-induced circulation and supported by downward mixing of momentum from the African Easterly Jet. triggered convection When the mature MCS approached the band from the cast it weakened. caused by increasine CIN ahead of the band Trieeering of convection on this day was favoured by drier surfaces and/or soil moistme inhomoffeneines. while a mature system weakened in the vicinity of a di le! surhice Thus a positive feedback between soil moisture and convection existed for a it system whereas a negative feedback was found for triggering of convection Copyright (C) 2009 Royal Meteorological Society