Weekly Seminar

The fate of airborne materials released in an urban area is affected by flows on many scales, including the basic synoptic-scale background flow and small-scale flows induced by buildings. When the city is located in mountainous or otherwise complex terrain, local scale topographically generated flows increase the complexity of the transport of the material. We present SF6 tracer data and Doppler lidar wind measurements from three nights when the tracer was released in downtown Salt Lake City. The larger-scale wind flow affected the formation of local-scale flows differently each night, which in turn affected the pattern of tracer dispersion in a different way each night.

The urban tracer experiment was embedded in a larger, basin-scale experiment, called the Vertical Transport and Mixing (VTMX) experiment, which was designed to study vertical transport mechanisms and the buildup and erosion of cold pools in a mountain basin. Overall objectives of VTMX will be reviewed, and the characteristics and effects of an unexpected, basin-scale, thermally forced, diurnal low-level jet will be presented.