Second EMEP ‑ WMO Workshop on Data / Dubrovnik, Croatia


Name:              Roland R. Draxler


Title:                 Meteorological Factors in Ozone Predictability




Several ozone modeling approaches were investigated to determine if

uncertainties in the meteorological data would be sufficiently large to

limit the application of more physically realistic ozone forecast models.  

Three predictive schemes were evaluated for the period of May through

September of 1997 at Houston, Texas.  Correlations between measured daily

maximum and model predicted ozone air concentrations were found to be 0.70

using a linear regression model, 0.65 using a non‑advective box model, and

0.49 using a 3‑Dimensional transport and dispersion model.  Although the

regression model had the highest correlation,  it showed substantial under‑

predictions of the highest concentrations. The  box model results were the

most similar to the regression model and did not show any under‑ prediction

bias. The more complex 3‑D modeling approach yielded the worst results,  in

part because ozone maximums were dominated by local factors rather than from

the transport of pollutants from outside of the Houston domain.   The

highest ozone concentrations at Houston were associated with light winds

and meandering trajectories.  A comparison of the gridded meteorological

data used by the 3‑D model to the observations showed that the wind

direction and speed values at Houston differed most on those days in which

the ozone under‑predictions were the greatest.   These periods also tended

to correspond with poor precipitation and temperature estimates. 


Date:                26 February 1999


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