Simple Models of Diabatically Forced Mesoscale Circulations and a Mechanism for Amplification

A two-dimensional, linear, Boussinesq, inviscid, hydrostatic model is used to simulate the flow over an elevated diabatic source and a surface diabatic source. The elevated source is identified as being due to cooling by melting, while the surface source is associated with land/sea temperature differences Melting frequently produces near-0øC isothermal layers. The atmosphere in this case tends to have strong static stability in the melting layer, capped by a much less stable layer aloft. This creates a strong change in the vertical wave number, which might lead to resonant amplification of mesoscale perturbations just as in mountain wave theory. Comparison with sounding data suggests that this amplification mechanism is potentially important for precipitation enhancement due to melting