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Satellite observations show that precipitating convective cloud systems in Earth's atmosphere tend to organize into spatially coherent structures embedded in fields of cumulus notably, but not only, in the Tropics. At a fundamental level this property is analogous to coherent structures in turbulent fluids. Although organization can occur in traditional climate models with 100s-km computational meshes, its morphology is usually not realistic. The reason for this misbehavior is two-pronged. Firstly, convective parameterizations were designed with turbulent mixing by transient cumulus in mind, and regardless of coherent convective systems. Secondly, the model resolution is too coarse to permit explicit systems. Organization involves interaction between diabatic heating, momentum transport, vertical shear and wave dynamics across a range of scales. We have excellent knowledge of the O(1km - 1000km) meso-synoptic range from field campaigns, cloud-system resolving models and dynamical analogs. Now that operational global weather models and experimental climate models both have O(10km) mesoscale-permitting meshes, we need to seriously consider the representation of organized convection in these models. Computational and theoretical insights are in place, and high-resolution global weather analyses in the form of a 'virtual global field campaign' provide useful information. The categories of organization featured in this talk are propagating convective systems over the continental United States and multiscale convective systems associated with the Madden-Julian oscillation, the leading mode of intraseasonal tropical variability.
This Seminar will be Webcast and here is the Webcast link http://www.fin.ucar.edu/it/mms/fl-live.htm