CAT (Clear Air Turbulence) Forecasting Using Transilient Turbulence Theory
Abstract
A transilient turbulence parameterization has been inserted into the regional three dimensional mesoscale numerical model. Transilient turbulence parameterizes both boundary layer and clear air turbulence (CAT). The new transilient turbulence scheme replaces separate formulations of the boundary layer parameterization, dry convective adjustment, cumulus parameterization and horizontal diffusion. A new surface layer flux formulation that is compatible with the transilient turbulence parameterization has also been installed. A sixth order implicit tangent filter has been inserted to remove numerical noise. This separation of the turbulence physics from numerical stability considerations gives us an opportunity to examine the mixing process in greater detail. Forecasts are compared from the revised model with the standard model formulation, which has a Blackadar boundary layer and fourth order K theory horizontal diffusion. Forecasts using both Kuo cumulus parameterization and explicit cloud convective representations have been made with this standard model utilizing the OSCAR IV data set. Comparisons between the control and the transilient turbulence approach are used to highlight the role of turbulence and its affect on the overall forecast. Verifying station radiosonde reports and analysis are the final authority on the accuracy of the forecasts. Early results suggests that some positive benefits will occur in the boundary layer forecasts once it is tuned to the surface flux calculations. Turbulence at higher levels is also predicted in our forecasts. The existence of this turbulence will be verified against both CAT and turbulence in storm systems.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 20, 1988
- Accession Number
- ADA198768
Entities
People
- Roland B. Stull
- William H. Raymond
Organizations
- University of Wisconsin–Madison