You are here:
DESIGN ARTIFACTS IN EULERIAN REGIONAL AIR QUALITY MODELS: EVALUATION OF THE EFFECTS OF LAYER THICKNESS AND VERTICAL PROFILE CORRECTION ON SURFACE OZONE CONCENTRATIONS
Citation:
Byun, D.W. AND R. Dennis. DESIGN ARTIFACTS IN EULERIAN REGIONAL AIR QUALITY MODELS: EVALUATION OF THE EFFECTS OF LAYER THICKNESS AND VERTICAL PROFILE CORRECTION ON SURFACE OZONE CONCENTRATIONS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-95/196, 1995.
Description:
Evaluation studies of the Regional Acid Deposition Model (RADM) results have revealed that there exists high bias of surface SO2 and O3 concentrations by the model, especially during nighttime hours. omparison of the RADM results with surface measurements of hourly ozone concentrations from the National Dry Deposition Network (NDDN) sites showed distinct diurnal variations in the model high bias. e hypothesize that this phenomenon is partly caused by the coarse vertical resolution of RADM in representing the deposition layer. he similarity theory of the Planetary Boundary Layer (PBL) can describe variation of the vertical profiles of a passive scalar with respect to atmospheric stability. or certain deposition species in the model, we can apply the PBL similarity theory to predict the high-bias of the model results (volume averages) to the surface observations (time series at a point) for the horizontally homogeneous case. he available hourly observations were limited and other complicating factors involved for several primary passive species. or example, although some observation sites were selected to be regionally representative, it was difficult to compare the observations directly with the RADM results of coarse horizontal resolution of 80 x 80. nstead, we applied the profile corrections to a secondary species O3, which is a very active reacting species even at night especially with NO. owever, we attempted to separate the affect of deposition layer thickness from the effects of other horizontal and vertical resolution such as emissions source distribution during the NO-O3 titration process for a clearer presentation of our hypothesis. he study shows that there are situations when a considerable portion of the high-bias of model O3 concentrations at night is explained by the coarse vertical resolution in the deposition layer. t is shown that the model should resolve, at least, the lower half of the PBL in order to predict surface deposition fluxes correctly. omparison with several NDDN observations shows that for certain NDDN sites the present hypothesis cannot fully explain the model's high-bias of daily minimum O3. n a companion paper, the effect of emission source distribution in representing the NO-O3 titration process will be studied to further investigate causes of the modal bias.