Adam H. Sobel
Department of Applied Physics and Applied Mathematics,
Department of Earth and Environmental Sciences,
LamontDoherty Earth Observatory,
Columbia University
Understanding deep convection by parameterizing largescale dynamics
Room 811 AOSS, May 2, 2016, 3:30 PM
Abstract
Tight coupling between deep convection and largerscale circulations in the atmosphere makes it difficult to understand the causal factors which control variations in precipitation on a range of space and time scales. One approach to untangling these factors involves simulating the convection in a small domain and parameterizing the large scale circulations which connect that domain to the rest of the atmosphere. The weak temperature gradient approximation is one such largescale parameterization, based on wellunderstood aspects of geophysical fluid dynamics near the equator and thus appropriate for the study of tropical convection. I will review application of the weak temperature gradient approach to a range of specific observed phenomena in the tropics, including El Nino, the MaddenJulian oscillation, and tropical cyclones. I will then present a new largescale parameterization appropriate outside the deep tropics, using the quasigeostrophic omega equation. A motivation for this latter work is to understand the dynamics behind extreme precipitation events in the subtropics and midlatitudes, and I will show results from its application to the events leading to the 2010 floods in Pakistan.
