Analytical Solution for the Convectively-Mixed Atmospheric Boundary Layer

Based on the prognostic equations of mixed-layer theory assuming a zeroth order jump at the entrainment zone, analytical solutions for the boundary-layer height evolution are derived with different degrees of accuracy. First, an exact implicit expression for the boundary-layer height for a situation without moisture is analytically derived without assuming any additional relationships or specific initial conditions. It is shown that to expand the solution to include moisture, only minor approximations have to be made. Second, for relatively large boundary-layer heights, the implicit representation is simplified to an explicit function. Third, a hybrid expression is proposed as a reasonable representation for the boundary-layer height evolution during the entire day. Subsequently, the analysis is extended to present the evolution of any boundary-layer averaged scalar, either inert or under idealized chemistry, as an analytical function of time and boundary-layer height. Finally, the analytical solutions are evaluated. This evaluation includes a sensitivity analysis of the boundary-layer height for the entrainment ratio, the free tropospheric lapse rate of the potential temperature, the time-integrated surface flux and the initial boundary-layer height and potential temperature jump.