Potential Vorticity in Mesoscale Convective Systems

With the renewed emphasis on potential vorticity as a dynamical variable in the mid-1980’s came the impetus for understanding the eventual geostrophic (balanced) ultimate state reached by complex weather systems involving organized, deep, moist convection. Wayne Schubert and his colleagues were at the forefront of this area of research in the late 1980’s through the late 1990’s. The long-term balanced response due to convection is a topic of practical importance especially for modeling the global circulation and the role of the redistribution of potential vorticity by diabatic processes in that circulation. Balanced structures intrinsically have a lifetime longer than the organized convection that gives rise to them, and hence carry a signature of convection forward in time long past the dissipation of the convection itself. Implicit is the net effect of all of the complex microphysics, turbulence and radiation that is operating in organized convection on the potential vorticity. This talk briefly reviews some of the elegant theory that Wayne and his colleagues produced. I will examine more recent observations in comparison with these theoretical results. Furthermore, I will examine the implications for global climate models now that they are reaching mesoscale-resolving capability.