Meteorological Evaluation of A Weather-chemistry Forecasting Model Using Observations From The Texas Aqs 2000 Field Experiment

Abstract

[1] Meteorological forecasts for the period of 25 - 30 August 2000 from a coupled weather-chemistry model are evaluated both qualitatively and quantitatively using the observations from different instruments that were deployed in metropolitan Houston during the Texas Air-Quality Study 2000 field experiment. The qualitative comparison is carried out with respect to the meteorological processes associated with the influence of the large-scale flow on the sea breeze that are essential to the development of the surface ozone exceedances over Houston, while the quantitative comparison is focused on the errors and uncertainties of the forecasts. The qualitative comparison is performed with respect to a conceptual model for the influence of the large-scale flow on the sea breeze. The comparison shows that although the overall forecasted influence of the large-scale flow on the sea breeze compares qualitatively well to the observations, quantitative differences do exist between the forecasted and observed wind speed and direction, as well as with temperature and moisture. It is found that the forecasted low-level winds have a systematic easterly bias and the forecasted low-level temperature has a cold bias. The errors in the forecasted low-level moisture appear relatively small, but with a cold bias they lead to higher relative humidity in the forecast than in reality. There is great sensitivity of the model forecasted low-level winds to different initial conditions. The quantitative comparison also indicates that the model's effective horizontal resolution corresponding to 1.67-km grid spacing is actually about 10 km.}