Advection Effects Near Changes in Surface Conditions

The concepts reviewed up to this point are applicable to study local evaporation from surfaces, which are sufficiently uniform and large, so that edge effects involving horizontal advection by the mean wind are relatively unimportant. The assumption of a horizontally homogeneous and steady boundary layer allows a one-dimensional treatment of the transport phenomena near the surface. However, under natural conditions, this assumption is often invalid. In the case of evaporation from surfaces of limited extent, such as finite-size lakes or irrigated areas surrounded by arid land, the horizontal inhomogeneity can be very important.