ACCOMMODATION BETWEEN TRANSPIRING VEGETATION AND THE CONVECTIVE BOUNDARY-LAYER

A simple scheme is developed to describe how vegetation and the convective boundary layer (CBL) interact during daylight in terms of water and sensible heat exchange. The response of vegetation to a prescribed atmospheric state is defined by a quadratic equation obtained by combining the Penman-Monteith equation with a new relation between surface conductance and transpiration rate based on laboratory evidence. The complementary response of the CBL to the input of sensible and latent at the ground surface is summarized by a simple relation between the Priestley-Taylor coefficient and surface conductance that fits daily mean values for diverse types of vegetation. The two responses are combined to provide a measure of 'accommodation' between vegetation and the atmosphere such that mean daily values of transpiration rate and saturation deficit can be obtained as functions of surface conductance and the net input of radiant heat.