Land Surface-Convective Precipitation Feedbacks: Theory and Application

Abstract

In this thesis, an intermediate-level complexity model of a coupled land-surface and atmospheric boundary layer is developed. The model is used to investigate the controls on soil moisture-precipitation feedbacks and vegetation biomass-precipitation feedbacks. The diurnal evolution of a well-mixed boundary layer with piece-wise linear profiles of potential temperature and specific humidity is modeled. Rainfall can (though is not guaranteed to) occur if the boundary layer height crosses the lifting condensation level and if the boundary layer height is sufficiently high relative to the Obukhov length. The model illustrates that precipitation occurrence is more sensitive to the free atmospheric humidity profile than to the free atmospheric temperature profile. The precipitation model is also coupled to a model of spatial vegetation patterns in the Sahel to investigate the timescales of vegetation pattern response to changes in rainfall regime. Land surface-precipitation feedbacks increase the sensitivity and rate of change of vegetation pattern morphology.