THE INFLUENCE OF HEAT AND MOISTURE FLUXES FROM THE OCEAN ON THE DEVELOPMENT OF BAROCLINIC WAVES

Numerical experiments using a two-dimensional primitive-equation nonhydrostatic model with idealized thermodynamics are performed to study the behavior of baroclinic waves in an environment that is saturated and subject to sensible and latent heat fluxes from the lower boundary. A slantwise convective adjustment is assumed to have occurred and reduced the base state to conditional symmetric neutrality. The model's perturbations exhibit two distinct phases of growth: an early stage of exponential growth, in which all the heating is confined to the boundary layer, followed by an "explosive" growth, almost linear with time, with deepening rates near or above the conventional definition of explosive cyclones. The onset of the explosive phase coincides with a hurricane-like structure in wind, temperature, and potential vorticity, which includes a narrow maximum of ?e at the center of the perturbation that expands as the development continues. An amplitude dependence for the transition to the "explosive" phase is suggested by the results of several experiments. The deepening rate in the explosive phase appears to increase almost linearly with the degree of air-sea thermodynamic disequilibrium.