Numerical simulations of the night 2 data of the 1980 ASCOT experiments in the California Geysers area

Abstract

A three-dimensional, time dependent hydrodynamic primitive equation model was used to simulate the distribution of nocturnal drainage winds, temperature, and turbulence in the California Geysers area. The case studied here (night 2) was under the condition that the ambient airflow was easterly and the direction of main drainage flow was westerly, The computed depth of drainage flow was less than 50 m at the ridge, and increased to 200 m at the valley, which agreed well with the observation. The computed wind speed at the ridge was smaller than the observation, but it agreed well at the valley site, Vertical wind variances measured by a doppler sodar indicated relatively large turbulence despite the fact that stable density stratification dominated throughout the night. The computed vertical wind variances were also larger than those observed over flat terrain, but smaller than the values recorded by the doppler sodar.