Mesoscale Convective System Parameterization for Global Climate Models

Deep convection frequently organizes into mesoscale convective systems (MCSs), however convective organization is not treated by traditional parameterizations for global climate models (GCMs). This historic deficiency adversely affects the type, intensity, distribution, and frequency of precipitation, impacts the regional and global water cycles, and compromises the efficacy of weather and climate models. Overcoming this key issue motivates the multiscale coherent structure parameterization (MCSP), a paradigm shift where mesoscale organization rooted in the principle of coherent dynamical structures in turbulent fluids is interlinked with sub-grid cumulus parameterization. The MCS is an important category of organized convection and observation-evaluated dynamical models of slantwise layer overturning provide transport modules. Because mesoscale circulations in MCSs are driven by pressure and vorticity gradients generated by families of sub-grid cumulus, it follows that the treatment of MCSs is GCMs is singularly a parameterization issue. Beneficial upscale effects of MCSP in GCM context improve convectively coupled Kelvin waves and the MJO, generate multiscale tropical precipitation systems consistent with TRMM satellite measurements, and suppress over-active cumulus parameterization. Finally, that MCSP is salient to other categories of organized deep convection and organized shallow convection, has far-reaching implications for convective parameterization in the future development of GCMs.