A Theoretical Study on the role of turbulent erosion in the breakup of cold air pools in basins

Cold air pools that form in basins and valleys in the wintertime can produce air pollution problems by trapping pollutants near the surface for multi-day periods. Understanding the mechanisms leading to cold pool formation and destruction is a problem of practical as well as scientific interest. Several mechanisms have been proposed to explain the breakup of cold air pools, including cold air advection aloft, frontal passages, turbulent erosion at the top of the pool, and surface heating from below. We have developed a theoretical model to investigate the turbulent erosion mechanism and have applied this model to cold pools forming over different topographical cross sections and with different atmospheric stratifications. For cold pools with a given terrain shape and stratification, the model allows us to estimate the time it would take for the turbulent erosion mechanism alone to destroy the cold pool as a function of the eddy mixing length scale and the wind speed above the cold pool.