Guidance for the Performance Evaluation of Three-Dimensional Air Quality Modeling Systems for Particulate Matter and Visibility

Abstract

Guidance for the performance evaluation of three-dimensional air quality modeling systems for particulate matter and IMPLICATIONS The National Ambient Air Quality Standards for particulate matter (PM) and the federal regional haze regulations place some emphasis on the assessment of fine particle (PM 2.5 ) concentrations. Current air quality models need to be improved and evaluated against observations to assess the reliability of model simulations. The guidance presented here provides the necessary framework for conducting rigorous performance evaluations of PM and visibility models. The costs associated with the field programs needed to obtain the data necessary for such performance evaluations are estimated to be $15 million for data collection (1-year program with an intensive program of 15 days, over 200,000 km 2 ) and $10-$20 million for planning, emission inventories, data analysis, and modeling. visibility is presented. Four levels are considered: operational, diagnostic, mechanistic, and probabilistic evaluations. First, a comprehensive model evaluation should be conducted in at least two distinct geographical locations and for several meteorological episodes. Next, streamlined evaluations can be conducted for other similar applications if the comprehensive evaluation is deemed satisfactory. In all cases, the operational evaluation alone is insufficient, and some diagnostic evaluation must always be carried out. Recommendations are provided for designing field measurement programs that can provide the data needed for such model performance evaluations.

Reconciliation and Interpretation of Big Bend National Park Particulate Sulfur Source Apportionment: Results from the Big Bend Regional Aerosol and Visibility Observational Study—Part I

“…Although the nudging of the boundary conditions to measurements for the CMAQ simulations improved CMAQ model performance for SO 2 , the data assimilation cannot completely overcome the difficulty of reproducing SO 2 concentrations at low values; this can be seen via comparison of the statistics for the mean normalized bias to the ratio of averages, which illustrate that the model was more capable of reproducing the overall SO 2 load during the analysis period. Overall, these statistics are commensurate with other sulfate modeling studies and within or near the acceptable limits proposed by Seigneur et al 39 …”

“…Standard model performance statistics were used, which are described elsewhere. 39 The following discussion focuses on the ratio of averages and the mean normalized error and bias. The mean normalized statistics tend to weigh errors in reproducing low observations to a greater degree than errors in reproducing high observations, because, at small concentrations, small absolute errors can lead to large relative errors.…”

Current Status of Air Quality Models for Particulate Matter

“…Seigneur et al 80 Because databases suitable for comprehensive model performance evaluation are limited, we recommend that models be evaluated according to a two-tiered approach. 80 First, a comprehensive evaluation should be conducted The results of the performance evaluations shown in Table 4 have been published in the peer-reviewed literature.…”

“…80 First, a comprehensive evaluation should be conducted The results of the performance evaluations shown in Table 4 have been published in the peer-reviewed literature. We judged to be poor due to large uncertainties in the emission inventories.…”

Chemical Mass Balance Model with Fractionation for Apportioning PM2.5: A Test Case for Los Angeles Traffic Sources

“…Visibility impairment in pristine areas is typically attributable to light scattering and absorption from fine particles. 2 A significant portion of fine particles is secondary, formed from gases during transport from the source to the receptor. For example, sulfur dioxide (SO 2 ) can be oxidized to sulfuric acid (SO 3 ) during atmospheric transport; the SO 3 then forms fine particles by nucleation and coagulation.…”