HR: 1340h
AN: A13B-0925    [Abstracts]
TI: New Approaches For Limiting Spurious Evaporation of Stratus Clouds
AU: * Reisner, J M
EM: reisner@lanl.gov
AF: Los Alamos National Lab, Los Alamos National Lab EES-2/D401, Los Alamos, NM 87544 United States
AB: In an Eulerian framework, spurious oscillations produced by advecting fields with unresolved gradients occasionally occur with these oscillations possibly being further amplified when the fields are introduced into forcing terms. An example of this problem that is of concern in atmospheric models is the advection and subsequent spurious evaporation of low-level clouds such as stratus. Note that stratus clouds extend over vast regions of the ocean surface and hence modeling their dependence on changes in external parameters such as greenhouse gases or aerosols is extremely important for understanding possible climate links. Previous attempts to minimize spurious evaporation near stratus clouds include the use of complex flux-corrected transport schemes, the tracking of cloud boundaries with the volume of fluid method, and employing high levels of numerical diffusion. While each of these approaches can occasionally prevent the evaporation of stratus clouds, they are not foolproof and suffer from certain pathological behaviors that have prevented their widespread use in cloud resolving models. Fortunately, two new approaches, a probability density function approach and a particle-based approach, have been recently developed that appear not to suffer from any of the problems of the previously attempted approaches, while still preventing the fictitious evaporation of cloud water. A description of both approaches along with simulations illustrating the evaporation limiting properties of either technique for a stratus deck observed during DYCOMS-II will be presented at the conference.
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005