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Abstract
Impressive advances have been made during recent decades in our knowledge of organized convection processes, notably the mesoscale convective system (MCS), but the parameterization of those processes in global climate models (GCMs) has languished. Being neither resolved nor parameterized, organized convection is omitted and thus missing from contemporary GCMs, so its effects on the large-scale environment remain to be quantified. . This omission is identified with the questionable general validity of the assumption of a scale-gap between the cumulus and the GCM grid which underpins cumulus parameterization -- MCSs occupy the gap. Cloud-system resolving modeling shows models show that organized convection in the Madden Julian Oscillation (MJO) is remarkably scale-invariant, i.e., squall lines, MCSs, and tropical superclusters tend to have similar dynamical structure and transport properties. In other words, the MCS-based parameterization can be generalized, albeit with due attention to the mean-state vertical wind-shear. In the The Multiscale Coherent Structure Parameterization (MCSP) is a new paradigm , that treats organized moist convection is conceived as coherent dynamical structures in the form of slantwise circulations that overturn entire atmospheric tropospheric layers (slantwise layer overturning), and is thereby distinguished from the mixing-based cumulus parameterization utilized in the turbulent environment of the coherent structures. With that approach, the The large-scale effects of convective organization are simply measured as the difference between GCMs GCM runs with and without MSCP. With Via the slantwise layer overturning as the transport module, MCSP generates large-scale coherence coherent structures in a state-of-the-art GCM. Specifically, a prototype MCSP implemented in the Community Atmosphere Model (CAM 5.5) provides an elementary proof-of-concept (Moncrieff et al. 2017). Consistent with the NASA TRMM 3B42 global precipitation database, the upscale effects of organized convective heating and momentum transport (in different ways) generate large-scale patterns of precipitation in the tropical warm-pool and maritime-continent regions. Precipitation distribution in the ITCZ, and the multiscale character of the MJO and convectively coupled tropical waves are improved. The MCSP paradigm, and its advancements, will be implemented in E3SM with emphasis on convective momentum transport and effects on tropical convection-wave interaction.
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