Effects of Cumulus Ensemble and Mesoscale Stratiform Clouds in Midlatitude Convective Systems

Abstract

Diagnostic and semiprognostic analyses are performed using OK PRE-STORM (Oklahoma-Kansas Preliminary Regional Experiment for STORM-Central) data to examine the cumulus-environment interaction in midlatitude convective systems. The similarities and differences of the interaction processes between midlatitude and tropical convective systems are also discussed: Analyses of PRE-STORM and GATE (GARP Atlantic Tropical Experiment) data show generally larger vertical wind shear, large-scale forcing, and moist convective instability in midlatitude MCCs (mesoscale convective complexes) and squall lines than in tropical cloud clusters. It is found that the interaction mechanism based on the cumulus-induced subsidence and detrainment is capable of explaining most of the observed heating and drying under widely different environment conditions. Convective- wale downdrafts act to cool and moisten the lower troposphere in the midlatitudes as in the tropics. The quasi- equilibrium assumption between stabilization by convection and destabilization by large-scale forcing is valid and holds better in the midlatitudes since the large-scale forcing is much stronger. Both the cumulus and stratiform cloud effects are stronger in midlatitude than in tropical convective systems.