Pergamon Atmospheric Environment Vol. 30, No. 12, pp. 2011-2025, 1996 Copyright C) 1996 Ehevier Science Lid Printed in Great Britain. All tights rmerv~ 1352-2310t96 $15.00+ 0.00 1353-2310(95) 00268-5 EFFECTS OF UNCERTAINTIES IN METEOROLOGICAL INPUTS ON URBAN AIRSHED MODEL PREDICTIONS AND OZONE CONTROL STRATEGIES G. SISTLA, N. ZHOU, W. HAO, J.-Y. KU and S. T. RAO Division of Air Resources, New York State Department of Environmental Conservation, Albany, NY 12233, U.S.A. R. BORNSTEIN and F. FREEDMAN Department of Meteorology, San Jose State University, San Jose, CA 95192, U.S.A. and P. THUNIS Environmental Institute, European Community Joint Research Institute, 21020 ISPRA, Italy (First received 21 Februm'y 1995 and in final form 12 June 1995) Almraet--Although wcll-rccngnized within the photochemical modeling community, the effect of uncer- tainties in meteorological input on the urban alrshed model (UAM) Output has not been systematically evaluated. In this study, the UAM has been applied to investigate the sensitivity of ozone predictions to the choices in wind fields and mixing height profiles for the data-sparse New York metropolitan area. A set of three wind fields, in combination with spatially varying and spatially invafiant mixing heights, is investi- gated for the July 1988 ozone episode. In general, mndei-predicted ozone levels were higher under the spatially varying mixing height (SVM) option than under the spatially invariant mixing height (SIM) option. SVM-based UAM simulations provided better agreement between the predicted and measured ozone concentrations than SIM-based UAM simulations. However, from the regulatory standpoint, predicted ozone concentrations based on either of these mixing height options are within the range considered as acceptable. UAM simulations with emission reductions of 75% NOx and 25% VOCs (NOx-focnsed) reveal that the improvement in peak ozone levels under the SIM option is larger than that under the SVM option, whereas the emission reduction scenario of 25% NOx and 75% VOCs (VOC- focused)yields greater improvement in peak ozone under the SVM option than with the SIM option. Given the strong influence of mixing heights and wind fields on UAM mode] predictions in data-sparse areas, it is imperative that uncertainties in development of ozone abatement plans be quantified. Copyright © 1996 Elsevier Science Ltd Key word index: Ozone control, UAM, meteorological inputs. l. INTRODUCTION Despite controls on the emissions of ozone precursors over the past two decades, ozone concentrations well above the health-based National Ambient Air Quality Standard CNAAQS) level of 0.12ppm continue to persist in urban areas in the northeastern United States. The New York metropolitan area, which en- compasses the urban areas of New York City (NYC), northern New Jersey, and southern Connecticut, of. ten experiences peak ozone levels exceeding 200 ppb. The Clean Air Act Amendments (CAAA) of 1990 attempted to deal with this continuing problem by requiting urban areas classified as serious and above to perform grid-based photochemical modeling ana- lyses to demonstrate attainment of the ozone stan- dard. To this end, the Environmental Protection Agency (EPA) has recommended use of urban airshcd model (UAM) for the preparation of ozone State Implementation Plans (SIPs). Besides the emissions inventory for UAM, the impact of meteorological input variables on model-predicted ozone concentra- tions needs to be carefully exzmined. When applying the UAM to satisfy EPA requirements, one may have insufficient measurements to define the detailed me- teorological conditions adequately for the modeled episode. In this case, there is a great deal of latitude in specifying the wind fields and mixing heights to the UAM. Given the sparsity of meteorological measurements in the New York metropolitan area, many possible representations of the wind fields and mixing heights 2011