A numerical study of a subtropical cloud free marine stable layer

Abstract

The processes acting to stabilize or destabilize a parcel of air can be partitioned and their individual contribution to the time rate of change of stability can be examined as a forcing to a stability equation. This study examines the trade wind inversion and is different from previous studies on the subject in that time dependent solutions of three dimensional non-linear equations are explored here. A quasi-geostrophic model is developed to simulate a typical large-scale environment in which a stable layer develops. Large-scale divergence forcing is found to be comparable to horizontal advection of stabilities in regions to the east of a subtropical low-level anticyclone. The level of maximum divergence forcing is found to be elevated in regions of upward heat flux from the ocean. Longwave radiative cooling from water vapor will increase the stability if the amount of water vapor decreases rapidly through the stable layer, however, the radiation will decrease the stability if the water vapor is well mixed through the stable layer.