18th Conference on Weather and Forecasting, 14th Conference on Numerical Weather Prediction, and Ninth Conference on Mesoscale Processes

Thursday, 2 August 2001
Mixing Processes and the Interaction among 3 Atmospheric Regimes in the Salt Lake City Basin
Gregory S. Poulos, Colorado Research Associates, Boulder, CO; and R. Hertenstein
Poster PDF (308.0 kB)
During the October, 2000 Vertical Mixing and Transport Experiment(VTMX) in the Salt Lake City Basin, a 3-regime atmospheric structure was observed by instruments deployed therein. The statically, and often dynamically, stable mosphere that typically characterized this partially enclosed complex terrain basin, was found to be subject to a forcing by primarily three components, 1) meso-beta to meso-gamma scale terrain induced flows, that generally etermined the surface layer characteristics and were esponsible for low-level mixing events, 2) meso-alpha scale basin-wide elevated jet-like flows, that created shear between the surface layer and the terrain maxima surrounding the basin, and 3) larger-scale, terrain-influenced synoptic flows, which induced mountain wave activity at upper levels and triggered gravity waves on the basin inversion. As a result, occassional significant mixing events would occur during what would otherwise appear to be a quiescent, dynamically stable overnight period. These events were the result of the combination of two or three destabilizing mechanisms within the 3-regime structure coinciding in space and time. Both observational and high-resolution (horizontal grid spacing of 400 m and vertical grid spacing of 15 m) mesoscale numerical modeling esults are discussed.

Supplementary URL: http://www.colorado-research.com/~gsp/VTMX