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Publications (29)8.63 Total impact

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    ABSTRACT: To comply with the federal 8-hr ozone standard, the state of Texas is creating a plan for Houston that strictly follows the U.S. Environmental Protection Agency's (EPA) guidance for demonstrating attainment. EPA's attainment guidance methodology has several key assumptions that are demonstrated to not be completely appropriate for the unique observed ozone conditions found in Houston. Houston's ozone violations at monitoring sites are realized as gradual hour-to-hour increases in ozone concentrations, or by large hourly ozone increases that exceed up to 100 parts per billion/hr. Given the time profiles at the violating monitors and those of nearby monitors, these large increases appear to be associated with small parcels of spatially limited plumes of high ozone in a lower background of urban ozone. Some of these high ozone parcels and plumes have been linked to a combination of unique wind conditions and episodic hydrocarbon emission events from the Houston Ship Channel. However, the regulatory air quality model (AQM) does not predict these sharp ozone gradients. Instead, the AQM predicts gradual hourly increases with broad regions of high ozone covering the entire Houston urban core. The AQM model performance can be partly attributed to EPA attainment guidance that prescribes the removal in the baseline model simulation of any episodic hydrocarbon emissions, thereby potentially removing any nontypical causes of ozone exceedances. This paper shows that attainment of all monitors is achieved when days with observed large hourly variability in ozone concentrations are filtered from attainment metrics. Thus, the modeling and observational data support a second unique cause for how ozone is formed in Houston, and the current EPA methodology addresses only one of these two causes.
    Journal of the Air & Waste Management Association (1995) 03/2011; 61(3):238-53. · 1.20 Impact Factor
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    ABSTRACT: Operational, diagnostic, and comparative evaluations of two one-atmosphere regional models were performed for the full calendar year 2002 in support of regional haze regulatory applications in the eastern US. Using consistent emissions, meteorological and air quality data sets, the community multi-scale air quality and comprehensive air quality model with extensions models were exercised on a nested 36/12 km grid system and evaluated across a broad range of time and space scales for numerous gas-phase and fine particulate species derived from routine and research-grade ambient measurements at six monitoring networks. Performance by both models for speciated fine particulate matter (PM) across the eastern US ranged from quite good (e.g., SO42−) to poor (e.g., soil). For most species, model bias was higher in the winter and lower (usually negative) in the summer suggesting potential issues related to vertical mixing (e.g., too little in winter), temporal allocation of emissions, and/or other model science processes or inputs. These results may be used to (a) guide one-atmosphere model refinements, (b) improve data input preparation procedures, (c) evaluate methods for rigorous, stressful performance testing, and (d) clarify the uncertainty in model estimates for regional haze and PM2.5 control strategy programs.
    Atmospheric Environment. 08/2006;
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    ABSTRACT: Photochemical grid models are being used in technical analyses by the Visibility Improvement State and Tribal Association of the Southeast (VISTAS), a regional air quality planning organization in the southeastern United States, to support state implementation plans for regional haze and related air quality issues. VISTAS has embarked on a multi-phase process of testing and evaluating regional meteorological, emissions and air quality models that will be used to project visibility improvements as required by the regional haze rule. VISTAS has generated 2002 annual emissions and meteorological inputs for two photochemical grid models, the community multi-scale air quality (CMAQ) and the comprehensive air-quality model with extensions (CAMx), at a 36 km resolution for the continental US and at 12 km resolution for the eastern US. The two models were evaluated using speciated PM measurements from various monitoring networks and detailed analysis was performed for organic carbon (OC) mass using the IMPROVE, STN, and SEARCH networks. The differences in model performance between CMAQ and CAMx were used as a diagnostic tool to investigate performance issues for several compounds. CAMx performed substantially better than CMAQ for OC (defined as 1.4×measured organic carbon) which led to investigations into methods for improving the CMAQ OC model performance. The treatment of secondary organic aerosol (SOA) was identified as an area needing improvements in both models. The impact of replacing the CMAQ SOA parameters with those from CAMx was investigated. Further analysis identified several processes that are potentially important for SOA formation that are not treated in either model including, polymerization of the SOA into non-volatile particles and SOA formation from sesquiterpene, isoprene and other biogenic VOCs. A prototype mechanism for several of these missing processes was developed and the CMAQ SOA module was enhanced to include these SOA formation processes. SOA yields, specifically from biogenic emissions, were increased by the modified SOA module and CMAQ model performance for particulate OC at the IMPROVE, SEARCH, and STN sites in the VISTAS region was improved.
    Atmospheric Environment. 01/2006;
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    ABSTRACT: The Visibility Improvement State and Tribal Association of the Southeast (VISTAS) is one of five Regional Planning Organizations that is charged with the management of haze, visibility, and other regional air quality issues in the United States. The VISTAS Phase I work effort modeled three episodes (January 2002, July 1999, and July 2001) to identify the optimal model configuration(s) to be used for the 2002 annual modeling in Phase II. Using model configurations recommended in the Phase I analysis, 2002 annual meteorological (Mesoscale Meterological Model [MM5]), emissions (Sparse Matrix Operator Kernal Emissions [SMOKE]), and air quality (Community Multiscale Air Quality [CMAQ]) simulations were performed on a 36-km grid covering the continental United States and a 12-km grid covering the Eastern United States. Model estimates were then compared against observations. This paper presents the results of the preliminary CMAQ model performance evaluation for the initial 2002 annual base case simulation. Model performance is presented for the Eastern United States using speciated fine particle concentration and wet deposition measurements from several monitoring networks. Initial results indicate fairly good performance for sulfate with fractional bias values generally within +/-20%. Nitrate is overestimated in the winter by approximately +50% and underestimated in the summer by more than -100%. Organic carbon exhibits a large summer underestimation bias of approximately -100% with much improved performance seen in the winter with a bias near zero. Performance for elemental carbon is reasonable with fractional bias values within +/- 40%. Other fine particulate (soil) and coarse particular matter exhibit large (80-150%) overestimation in the winter but improved performance in the summer. The preliminary 2002 CMAQ runs identified several areas of enhancements to improve model performance, including revised temporal allocation factors for ammonia emissions to improve nitrate performance and addressing missing processes in the secondary organic aerosol module to improve OC performance.
    Journal of the Air & Waste Management Association (1995) 12/2005; 55(11):1694-708. · 1.20 Impact Factor
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    04/2004;
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    ABSTRACT: This study assesses the potential influence compensating errors in photochemical model inputs may have on estimates of the effects of emission control scenarios. Motivation stems from the apparent ability to achieve satisfactory model performance despite evidence suggesting the existence of significant biases in emissions estimates. Urban Airshed Model (UAM) sensitivity studies were carried out using simulations of two summer 1987 O3 episodes in the South Coast Air Basin of California. Since existing simulations exhibited inadequate performance, efforts were made to rectify these problems. Plausible conditions that might define acceptable base cases were established, and model runs were made to determine which alternative base cases provided a level of UAM performance comparable to the best achieved for the two summer episodes. The alternative base cases produced different estimates of the air quality benefits associated with hypothetical emission control scenarios. For example, one set of base cases indicated that NOx, controls would be counterproductive in helping to reduce the estimated peak O3 concentration in the eastern portion of the modeling domain. Another base case suggested that such controls would yield almost no change in the peak value. The results from alternative base case simulations provide a lower bound estimate of the uncertainty that attends future year modeling results. Such analyses should be incorporated into current photochemical modeling practice.
    Atmospheric Environment 06/1996; 30(12). · 3.11 Impact Factor
  • 01/1991;
  • T. W. Tesche, Dennis E. McNally
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    ABSTRACT: Data collected during the 1984 SCCCAMP Exploratory Study were used to develop two multiple-day ozone modeling episodes for the Urban Airshed Model (UAM). An operational model performance evaluation was performed for the 5-7 and 16-17 September 1984 episodes. Peak 1-h average ozone concentrations were reproduced on the five simulation days with accuracies (paired in time and space) ranging from 0% to 30%. The mean bias in hourly averaged ozone concentrations ranged from 6% to +11%, and the mean gross errors varied between 23% and 38%. UAM performance for ozone concentrations with the two September episodes is comparable with other recent photochemical model evaluations. Lack of sufficient measurements for model performance testing of other important photochemical species (e.g., NO, NO2, volatile organic compounds) and for carrying out compensatory error analysis and related diagnostic and mechanistic investigations precluded a more rigorous scientific evaluation of UAM performance with the 1984 SCCCAMP database.
    Journal of Applied Meteorology 01/1991; 30:745-745.
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    ABSTRACT: The study establishes a set of procedures that should be used by all groups evaluating the performance of a photochemical model application. A set of ten numerical measures are recommended for evaluating a photochemical model's accuracy in predicting ozone concentrations. Nine graphical methods and six investigative simulations are also recommended to give additional insight into model performance. Standards are presented that each modeling study should try to meet. To complement the operational model evaluation procedures, several diagnostic procedures are suggested. The sensitivity of the model to uncertainties in hydrocarbon emission rates and speciation, and other parameters should be assessed. Uncertainty bounds of key input variables and parameters can be propagated through the model to provide estimated uncertainties in the ozone predictions. Comparisons between measurements and predictions of species other than ozone will help ensure that the model is predicting the right ozone for the right reasons. Plotting concentrations residuals (differences) against a variety of variables may give insight into the reasons for poor model performance. Mass flux and balance calculations can identify the relative importance of emissions and transport. The study also identifies testing a model's response to emission changes as the most important research need. Another important area is testing the emissions inventory.
    07/1990;
  • 01/1988: pages -; California Institute of Technology.
  • T. W. Tesche
    Journal of Environmental Engineering-asce - J ENVIRON ENG-ASCE. 01/1988; 114(4).
  • T.W. Tesche, J.L. Haney, R.E. Morris
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    ABSTRACT: Four numerical grid-based dispersion models (Mathew/ADPIC, SMOG, Hybrid, and 2DFLOW) were adapted to the Geysers-Calistoga geothermal area in northern California. The models were operated using five intensive meteorological and tracer diffusion data sets collected during the 1981 ASCOT field experiment at the Geysers (three nocturnal drainage and two daytime valley stagnation episodes). The 2DFLOW and Hybrid Models were found to perform best for drainage and limited-mixing conditions, respectively. These two models were subsequently evaluated using data from five 1980 ASCOT drainage experiments. The Hybrid Model was also tested using data from nine limited-mixing and downwash tracer experiments performed at the Geysers prior to the ASCOT program. Overall, the 2DFLOW Model performed best for drainage flow conditions, whereas the Hybrid Model performed best for valley stagnation (limited-mixing) and moderate crossridge wind conditions. To aid new source review studies at the Geysers, a series of source-receptor transfer matrices were generated for several different meteorological regimes under a variety of emission scenarios using the Hybrid Model. These matrices supply ready estimates of cumulative hydrogen sulfide impacts from various geothermal sources in the region.
    Atmospheric Environment (1967). 01/1987;
  • T.W. Tesche, J.L. Haney, R.E. Morris
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    ABSTRACT: This study utilized data collected during 5 tracer experiments to test the predictive performance of two numerical, grid-based complex-terrain dispersion models - the 2DFLOW and Hybrid models. The 2DFLOW model was developed by researchers at Savannah River National Laboratory (Garrett and Smith, 1982, 1984); the Hybrid model was developed by Systems Applications, Inc., and has been applied to air quality problems and in model evaluation studies for several years (Tesche, 1983). This study closely parallels a more extensive model evaluation effort at The Geysers in which four models - Mathew, ADPIC, SMOG, Hybrid, and 2DFLOW - were evaluated with additional tracer experiments from the 1981 ASCOT program and from earlier tracer studies conducted between 1878 to 1980 (Tesche, Haney, and Morris, 1984a,b; Tesche, 1984). In Section 2, we provide a brief overview of the theoretical formulation of the 2DFLOW and Hybrid models. Section 3 presents simulation results for each model for the five 1980 ASCOT drainage experiments. We interpret these results in Section 4 and present our findings and conclusions in Section 5.
    10/1984;
  • Journal of Environmental Engineering-asce - J ENVIRON ENG-ASCE. 01/1984; 110(1).
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    ABSTRACT: The purpose of this study is to evaluate the effect of reductions of reactive organic gases (ROG) and NOx emissions on short-term O3 and NO2 concentrations and annual average NO2 concentrations in the California South Coast Air Basin. Short-term air quality predictions were obtained by applying the Systems Applications Airshed Model to summer O3 and autumn NO2 episodes. Effects of emission controls on annual NO2 concentrations were estimated using CDM and a new parcel tracking model NOXTRAK. Results for the summer O3 episode indicate that ROG emission reduction in an effective means for reducing peak O3 concentrations. NOx emission reduction imposed in addition to ROG emission reductions are counterproductive in reducing peak O3 concentrations. The modeling results also suggest that attainment of the 1-h federal O3 standard requires ROG emission reductions on the order of 80% from 1987 levels. Results for the autumn NO2 episode indicate that NOx emission reductions approximating those recommended in a proposed Air Quality Management Plan (about 22%) will result in only small (about 5%) reductions in the peak NO2 concentrations. ROG emission reduction may be more effective than NOx emission reduction in reducing the peak NO2 concentration. For the episode studied, a reduction of 36% in ROG emissions is estimated to result in a reduction in peak NO2 concentrations commensurate with that required to attain the 1-h state NO2 standard. Model calculations also indicate that the federal NO2 standard may not be meet by 1987 at one or two stations, but may blosely approached.
    Environment International - ENVIRON INT. 01/1983; 9(6):549-571.
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    ABSTRACT: This paper presents the development and evaluation of an urban air quality model, the Plume-Airshed Reactive-Interacting System (PARIS), that is capable of providing a detailed treatment of large point source emissions. The PARIS model treats these large point sources by embedding one or more reactive plume models into the Systems Applications urban airshed model, which is a three-dimensional gridded model governed by the atmospheric diffusion equation. These embedded reactive plume models are used to decribe the chemistry and dynamics of large point source plumes and their interaction with the ambient urban environment. When the plume size becomes comparable to the airshed model grid cell size, a subgrid scale description is no longer necessary and the plume material is mixed into the airshed model grid cells.For purposes of evaluation and comparison, the Systems Applications urban airshed model and the PARIS model were applied to the St. Louis urban area for a one-day simulation and to the South Coast Air Basin (Los Angeles area) for a two-day simulation. Overall absolute errors between predictions and observations for the urban airshed and PARIS model simulations are on the order of 40–50% for O3 and NO2 concentrations. The overall differences in absolute errors between airshed and PARIS model predictions are between 1 and 5 %; the difference in overall model performance resulting from the PARIS model subgrid scale treatment of point sources is well within measurement uncertainties for both O3 and NO2 concentrations. These results indicate that for these two applications, detailed treatment of large point sources with the PARIS model has little effect on overall model performance. However, the model can provide information necessary for the study of the impact of individual point sources located in an urban environment.
    Atmospheric Environment 01/1983; · 3.11 Impact Factor
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    ABSTRACT: Using the air quality, meteorological and emissions data base available in the Los Angeles area, two days with distinctly different meteorology are simulated using a photochemical grid model (Urban Airshed Model). The data base used to generate model inputs is then degraded for the purpose of noting which data are most essential to collect in order to have a complex grid model perform adequately. The results are used to develop a more general methodology for prioritizing data needs. The methodology considers model sensitivity to input derived from data bases of varying detail, expense in collecting the data, and the uncertainty associated with deriving model input variables from the data base.
    08/1981;
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    ABSTRACT: In recent years, urban-scale photochemical simulation models have been developed that are of practical value for predicting air quality and analyzing the impacts of alternative emission control strategies. Although the performance of some urban-scale models appears to be acceptable, the demanding data requirements of such models have prompted concern about the costs of data acquisition, which might be high enough to preclude use of photochemical models for many urban areas. To explore this issue, sensitivity studies with the Systems Applications, Inc. (SAI) Airshed Model, a grid-based time-dependent photochemical dispersion model, have been carried out for the Los Angeles basin. Reductions in the amount and quality of meteorological, air quality and emission data, as well as modifications of the model gridded structure, have been analyzed. This paper presents and interprets the results of 22 sensitivity studies. A sensitivity-uncertainty index is defined to rank input data needs for an urban photochemical model. The index takes into account the sensitivity of model predictions to the amount of input data, the costs of data acquisition, and the uncertainties in the air quality model input variables. The results of these sensitivity studies are considered in light of the limitations of specific attributes of the Los Angeles basin and of the modeling conditions (e.g., choice of wind model, length of simulation time). The extent to which the results may be applied to other urban areas also is discussed.
    Journal of Applied Meteorology 08/1981; 20:1020-1040.
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    ABSTRACT: Photochemical grid models are being used in technical analyses by the Visibility Improvement State and Tribal Association of the Southeast (VISTAS), a regional air quality planning organization in the southeastern United States, to support state implementation plans for regional haze and related air quality issues. VISTAS has embarked on a multiphase process of testing and evaluating regional meteorological, emissions and air quality models that will be used to project visibility improvements as required by the regional haze rule. VISTAS has generated 2002 annual emissions and meteorological inputs for two photochemical grid models, the community multi-scale air quality (CMAQ) and the comprehensive air-quality model with extensions (CAMx), at a 36 km resolution for the continental US and at 12 km resolution for the eastern US. The two models were evaluated using speciated PM measurements from various monitoring networks and detailed analysis was performed for organic carbon (OC) mass using the IMPROVE, STN, and SEARCH networks. The differences in model performance between CMAQ and CAMx were used as a diagnostic tool to investigate performance issues for several compounds. CAMx performed substantially better than CMAQ for OC (defined as 1.4 x measured organic carbon) which led to investigations into methods for improving the CMAQ OC model performance. The treatment of secondary organic aerosol (SOA) was identified as an area needing improvements in both models. The impact of replacing the CMAQ SOA parameters with those from CAMx was investigated. Further analysis identified several processes that are potentially important for SOA formation that are not treated in either model including, polymerization of the SOA into non-volatile particles and SOA formation from sesquiterpene, isoprene and other biogenic VOCs. A prototype mechanism for several of these missing processes was developed and the CMAQ SOA module was enhanced to include these SOA formation processes. SOA yields, specifically from biogenic emissions, were increased by the modified SOA module and CMAQ model performance for particulate OC at the IMPROVE, SEARCH, and STN sites in the VISTAS region was improved. (c) 2006 Elsevier Ltd. All rights reserved.
    Atmospheric Environment. 40(26):4960-4972.
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    ABSTRACT: A key component of the SJVAQS/AUSPEX Regional Modeling Adaptation Project (SARMAP) is a meteorological model based on the Penn State/NCAR MM5 nonhydrostatic mesoscale modeling system. Using the Penn State four-dimensional data assimilation (FDDA) system, the model produces realistic simulations of atmospheric conditions throughout a five-day high ozone episode. The two numerical experiments reported here use three nested domains of 36-km, 12-km and 4-km resolution and 30 layers in the vertical. In the first experiment, synoptic- scale analyses based on standard weather service radiosondes and surface stations are assimilated on the 36-km and 12-km domains, but no data assimilation is done on the 4-km domain. This experiment shows fairly good agreement with observed winds and temperatures over California, although the mixing depths in the San Joaquin Valley are too deep. In the second experiment, FDDA techniques were used to directly assimilate special data from about 50 soundings and about , 120 surface stations in addition to the analyses assimilated in the first experiment. These special data, applied on the 12-km and 4-km domains only, were found to significantly reduce the large errors in mixing depths, as well as improving low level temperatures and winds.