Evaluation of Meteorological Models MM5 and HOTMAC Using PAFEX-I Data

Abstract

Two meteorological models, the fifth-generation Pennsylvania State University?National Center for Atmospheric Research Mesoscale Model (MM5) and the hydrostatic version of the Higher-Order Turbulence Model for Atmospheric Circulation (HOTMAC), were employed to simulate circulation and surface temperature in the Phoenix, Arizona, valley under weak synoptic forcing. The performances of these models were evaluated using field data collected during the first Phoenix Air Flow Experiment (PAFEX-I). MM5 showed a reasonable agreement with observations of the surface energy budget and surface temperature. The local flow, which was largely governed by thermodynamics, was also simulated well by MM5. In HOTMAC, a relatively uniform wind field was attributed to hydrostatic dynamics, active vertical mixing, and the zero-gradient lateral boundary condition used. The cold bias observed in HOTMAC results appears to be caused by the attenuation of shortwave irradiance within the canopy layer and the assumption of horizontal homogeneity in initialization. Differences in the formulation of surface energetics of the two models were examined and compared quantitatively. Statistical analysis of model performance showed that MM5 results are the closest to the observations.