An investigation of Mesoscale Flows Induced by Vegetation Inhomogeneities Using an Evapotranspiration Model Calibrated Against HAPEX-MOBILHY Data

Abstract

Many recent studies have suggested that heterogeneities in soil properties or vegetation characteristics many trigger mesoscale circulations in planetary boundary layer (PBL). Unfortunately, these flows appear to be very sensitive to the choice of the model characteristics and therefore require a careful calibration of the parameterization representing the vegetation/atmosphere interface. In this paper, the micrometeorological data from the HAPEX-MOBILHY field experiment are used to calibrate an evapotranspiration parameterization scheme over three types of dense vegetation typical of western Europe. This parameterization is then used a 2D mesoscale model to investigate the atmospheric response to a discontinuity in vegetation type (cereal crop to conifer forest). The results show a significant circulation when the soil is moist, associated with substantial PBL modification, whereas only a negligible atmospheric response is obtained when the soil is dry in the conifer forest). The results show a significant circulation when the soil is moist, associated with substantial PBL modification, whereas only a negligible atmospheric response is obtained when the soil is dry in the cereal crop area. A precise knowledge of the soil moisture therefore appears to be required, even with dense vegetation cover, to use advanced evapotranspiration schemes in mesoscale models.