An Evaluation of Mesoscale Model Predictions of Down-Valley and Canyon Flows and Their Consequences Using Doppler Lidar Measurements during VTMX 2000

Abstract

Abstract A mesoscale model, a Lagrangian particle dispersion model, and extensive Doppler lidar wind measurements during the Vertical Transport and Mixing (VTMX) 2000 field campaign were used to examine converging flows over the Salt Lake valley in Utah and their effect on vertical mixing at night and during the morning transition period. The simulated wind components were transformed into radial velocities to make a direct comparison with about 1.3 million Doppler lidar data points and to evaluate critically the spatial variations in the simulated wind fields aloft. The mesoscale model captured reasonably well the general features of the observed circulations, including the daytime up-valley flow; the nighttime slope, canyon, and down-valley flows; and the convergence of the flows over the valley. When there were errors in the simulated wind fields, they were usually associated with the timing, structure, or strength of specific flows. The simulated flow reversal during the evening transition period prod...