SURFACE-FLUX REGULATION OF THE COUPLING BETWEEN CUMULUS CONVECTION AND BAROCLINIC WAVES

The authors examine the rule of convection in the dynamics of eddy lif e cycles through numerical experiments using initial states that are b aroclinically and conditionally unstable in midlatitudes. The location of wave-induced connection and its influence on the growing wave depe nds on how strongly the wave is coupled to the lower boundary through surface fluxes. For all three convective schemes used here (Emanuel, m odified Grell, modified Kuo), convective destabilization is favored in the wave's warm sector when there are no surface flukes included in t he simulation and in the cold sector when there are. Convection is als o shallower when it occurs in the cold sector. though still precipitat ing. For simulations using Emanuel convection. the relatively shallow convection plays a central role in a water cycle wherein 1) evaporatio n gives moisture to the cold sector's boundary layer, 2) convection pu mps some of the moisture into the lower troposphere above the boundary layer, 3) the large-scale circulation transports the moisture eastwar d and upward into the wave's warm sector. and 4) stable precipitation condenses the moisture into precipitation. The additional condensation catalyzes a more energetic lie cycle by inducing stronger vertical mo tion and, hence, a greater conversion of available potential energy to kinetic energy. This enhancement, however, is parameterization depend ent. with tile key factor being how much lower-tropospheric moistening a convection scheme produces.