Theoretical Modeling Studies of the Marine Planetary Boundary Layer
Abstract
A new type of boundary-layer model is developed to combine second- order closure with a bulk presentation of the verticle structure. The boundary layer depth and turbulence kinetic energy (TKE) are prognostically determined. The large turbulent eddies that are primarily responsible for the fluxes are modeled as convective circulations, with ascending and descending branches. The upper part of the attached figure illustrates the structure of the PBL as represented in the model. The interior of the boundary layer is bounded above by a thin entrainment layer and below by a thin ventilation layer. Conservative variables such as the equivalent potential temperature have quadratic profiles in the interior. Convective circulations occur, with rising branches occupying fractional area sigma, which is predicted by the model. The lower panel is a plot of the fractional area covered by rising motion, sigma, as a function of the ratio of the entrainment rate to the ventilation rate. As indicated in the figure, the model predicts that as the entrainment rate increases the fractional area covered by rising motion decreases; rapid entrainment is associated with small sigma. One hopes to gain an improved theoretical understanding of and predictive capability for partly cloudy boundary layers, and to test these ideas against data acquired in the field. Also, to investigate the role of air-sea interactions in regulating cloud amount in the marine boundary layer.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 31, 1989
- Accession Number
- ADA217200
Entities
People
- David A. Randall
Organizations
- Colorado State University