Vertical-Velocity Distributions as a Key to Representing Convection across Sub-Grid Scales in Climate Models

Friday, 19 December 2014: 4:30 PM
Leo Donner, Geophysical Fluid Dynamics Laboratory, Princeton, NJ, United States
The complex, multi-scale character of convective systems, ranging from
microphysical to planetary scales, remains a major modeling challenge.
Meeting this challenge requires advances in high-resolution dynamical
modeling and accurate representation of microphysical, radiative, and
sub-grid dynamical processes. A unifying theme among these elements is
provided by vertical velocities, which distinctly characterize the dynamics
of the various components of the convective systems and drive many of their
aerosol and microphysical processes.

Only recently has an observational basis for understanding vertical
velocities in convective systems become available. These observations
provide constraints on both high-resolution models of convection and
parameterizations used in coarser-resolution models. Accurate treatments of
microphysics and turbulence, along with sufficiently high resolution, appear
necessary for cloud-resolving models to simulate vertical velocities
realistically. Parameterized vertical velocities for coarse-resolution models, based on
higher-order closure methods including dynamics and assumptions about
generality of entrainment, are only now coming under scrutiny. A concerted
effort to refine cloud-resolving models so they can simulate vertical
velocities realistically and serve as benchmarks for parametric methods is