Numerical investigation of mesoscale circulations over the Los Angeles basin. Part II: synoptic influences and pollutant transport

Abstract

Light large-scale winds had little influence on the strong summertime mesoscale circulations, but stronger large-scale winds exerted considerable influence on the weak mesoscale wintertime circulations. During both seasons, daytime upslope flows near the mountains ventilate the basin, inducing basinwide airflow and augmenting the sea breeze. Air from the basin's planetary boundary layer (PBL) travels upslope and rises over the ridgetops, where it mixes convectively to great heights; winds aloft then transport the air from the region. Only in one simulation did the heated-slope circulations inject pollutants into the inversion layer. Significant flows through the three major mountain passes occur, with subsequent mixing in the desert PBL. -from Authors