Citation:

Byun, D.W. AND R. Dennis. INFLUENCE OF VERTICAL RESOLUTION ON THE DIURNAL OZONE CONCENTRATIONS IN A REGIONAL PHOTOCHEMICAL MODEL: A PRELIMINARY STUDY WITH WINDOW RADM. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/A-93/289 (NTIS PB94130093), 1993.

Description:

Evaluation studies of the Regional Acid Deposition Model (RADM) with surface measurement have revealed positive bias (overprediction) of surface ozone (O3) concentration during nighttime hours and negative bias (underprediction) during daytime hours by the model, especially in rural areas. e hypothesize that this phenomenon is partly caused by the coarse vertical resolution of RADM in representing emissions distribution.We introduce a coupled set of nondimensional ordinary differential equations representing the O3-NO titration process after the photochemical reactions have ceased. he analysis shown that the rate of 03 destruction can be influenced considerably by the NO emissions strength as well an the dry deposition process. y comparing the O3, titration rates and NO concentrations in RADM and observations, we conclude that surface NO emissions in RADM are not well represented. esides the uncertainties in the NOx emissions database, the other possible explanation for the apparent low NO concentrations in the surface layer at nighttime is that the emissions are distributed too rapidly in the coarse vertical layer. e have tested this hypothesis by introducing a surface-emissions layer into a limited-domain RADM (WRADM). he results show that ,he det&ils of vertical gradients in the emissions distribution are very important in explaining the nighttime model bias. his preliminary study provides one example of the need for adequate vertical resolution in the photochemical modal in minimizing the model bias.

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