Simulation of the sea-breeze front with a model of moist convection

Abstract

Although in general the sea breeze can be considered as a mesoscale atmospheric circulation, the sea-breeze front has a much smaller scale. Simulation of the development of a sea-breeze front should therefore be preferably done with a non-hydrostatic model, with high spatial resolution (grid distances of a few hundred meters). Here we describe an attempt to do this. We conducted a few numerical experiments to study in an explicit way the effect of convective cloud formation on the evolution of the sea-breeze front. The model used is a 2-D cloud model, applied to a domain 60 km long and almost 4 km high, with a resolution of 250 m. Integrations were carried out over 4 h of simulated time.

We found that even with only a weak offshore background wind (1 m/s), the sea breeze rapidly takes on the form of a gravity current with a well-developed head. A comparison of runs with and without cloud simulation revealed that the formation of clouds tends to strengthen the sea breeze. The reason is that convective clouds form over land or just above the sea-breeze front, and dissipate at the seaward side of the front. The net effect is an additional horizontal gradient in diabatic heating.