T. W. Tesche

National Center for Atmospheric Research, Boulder, Colorado, United States

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Publications (32)42.44 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.
    No preview · Article · Mar 2011 · Journal of the Air & Waste Management Association (1995)
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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.
    No preview · Article · Aug 2006 · Atmospheric Environment
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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.
    Full-text · Article · Aug 2006 · Atmospheric Environment
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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.
    Full-text · Article · Aug 2006 · Atmospheric Environment
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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.
    No preview · Article · Dec 2005 · Journal of the Air & Waste Management Association (1995)
  • Philip M Roth · Steven D Reynolds · Thomas W Tesche
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    ABSTRACT: Despite the widespread application of photochemical air quality models (AQMs) in U.S. state implementation planning (SIP) for attainment of the ambient ozone standard, documentation for the reliability of projections has remained highly subjective. An "idealized" evaluation framework is proposed that provides a means for assessing reliability. Applied to 18 cases of regulatory modeling in the early 1990s in North America, a comparative review of these applications is reported. The intercomparisons suggest that more than two thirds of these AQM applications suffered from having inadequate air quality and meteorological databases. Emissions representations often were unreliable; uncertainties were too high. More than two thirds of the performance evaluation efforts were judged to be substandard compared with idealized goals. Meteorological conditions chosen according regulatory guidelines were limited to one or two cases and tended to be similar, thus limiting the extent to which public policy makers could be confident that the emission controls adopted would yield attainment for a broad range of adverse atmospheric conditions. More than half of the studies reviewed did not give sufficient attention to addressing the potential for compensating errors. Corroborative analyses were conducted in only one of the 18 studies reviewed. Insufficient attention was given to the estimation of model and/or input database errors, uncertainties, or variability in all of the cases examined. However, recent SIP and policy-related regional modeling provides evidence of substantial improvements in the underlying science and available modeling systems used for regulatory decision making. Nevertheless, the availability of suitable databases to support increasingly sophisticated modeling continues to be a concern for many locations. Thus, AQM results may still be subject to significant uncertainties. The evaluative process used here provides a framework for modelers and public policy makers to assess the adequacy of contemporary and future modeling work.
    No preview · Article · Nov 2005 · Journal of the Air & Waste Management Association (1995)
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    Full-text · Article · Apr 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.
    No preview · Article · Jun 1996 · Atmospheric Environment
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    ABSTRACT: Air quality models serve as the foundation for policy decisions regarding programs designed to improve air quality. The California Air Resources Board Airshed Model (CALGRID) is one of the latest photochemical air quality models developed for assessing ozone control strategies. CALGRID was modified to include the lates CBIV chemical mechanism in place of the original SAPRC mechanism. After modification, a detailed evaluation of CALGRID was carried out using two different ozone episodes. The first evaluation used data obtained during the Southern California Air Quality Study (SCAQS). The second evaluation used data obtained for the September, 1984 SCCCAMP episodes in the South Central Coast Air Basin (SCCAB). Model results were compared against observations of O3, NO, NO2, and different organic compounds. For the SCCAB episode, the results were also compared with those obtained from the Urban Airshed Model (UAM). Similar to other studies, the ozone predictions from the SCAQS application were biased low, as were various ROG components. The reason for this can be linked to the under-representation of ROG and CO in the emissions inventory. For the SCCAB episode, both the UAM and CALGRID models significantly underestimated NO and NO2 concentrations. The two models slightly underestimated ozone concentrations above approximately 9 pphm on the third and last day of the simulation. Sensitivity experiments were performed for both the studies. It was found that both CALGRID and UAM are strongly sensitive to the boundary conditions and moderately sensitive to the emissions for the episodes modeled.
    No preview · Article · Sep 1994 · Atmospheric Environment
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    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.
    Preview · Article · May 1991 · Journal of Applied Meteorology

  • No preview · Chapter · Jan 1991
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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.
    No preview · Article · Jul 1990
  • T. W. Tesche
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    ABSTRACT: Photochemical grid model performance evaluation studies have been undertaken over the last decade as an integral part of ozone air pollution model development and application efforts and in support of model sensitivity analysis, monitoring program design, and applied research. These studies, sponsored by federal and state agencies, universities, and consulting firms, represent a significant body of information. A comprehensive review of past Eulerian model evaluation studies indicates that the overall accuracy of hourly averaged ozone predictions, paired in time and space, is of the order of 35-40%. However, considering the model's ability to reproduce the maximum observed concentration, independent of time or space pairing, overall prediction accuracies of 10−20% are found. For single-day ozone simulations, the overall negative bias is −10%.
    No preview · Article · Aug 1988 · Journal of Environmental Engineering

  • No preview · Book · Jan 1988
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    T.W. Tesche
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    ABSTRACT: Several recent studies have examined the accuracy of alternative numerical schemes for solving the species conservation equation applied to tropospheric air pollution problems. These studies have centered mainly on the use of simplified numerical experiments involving the advection of different initial concentration distributions (e.g. a cosine hill). Few studies report comparative evaluation of alternative numerical schemes using established photochemical modeling data bases for realistic urban settings. This study presents a comparison of two contemporary schemes—SHASTA and the multidimensional flux correction method of Zalesak—applied to the Los Angeles, Calif. and Philadelphia, Pa urban areas. The results indicate that, for the conditions examined, the Zalesak method gives slightly more accurate peak ozone predictions than the SHASTA method in applications to Los Angeles (where peak ozone levels are three times the federal standard). For the more moderate ozone conditions found in Philadelphia, very little difference in accuracy is seen between the two methods.
    Preview · Article · Dec 1987 · Mathematical Modelling
  • 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.
    No preview · Article · Jan 1987 · Atmospheric Environment (1967)
  • 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.
    No preview · Article · Oct 1984
  • T. W. Tesche · C. Seigneur · W. R. Oliver · J. L. Haney
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    ABSTRACT: Attempts by various local, state, and federal agencies to quantify the degree of emission reductions in Los Angeles, California needed to attain the federal ozone standard have recently been extended to include the use of sophisticated air pollution simulation models. In particular, the Systems Applications Airshed Model—a grid-based, time-dependent photochemical simulation model—has been applied to the region in recent air management studies. After initial model verification analysis using field measurements obtained during an historical smog episode in southern California, the model was used to evaluate the impacts on future ozone levels of alternative emission controls for principal ozone precursors i.e., reactive organic gases and oxides of nitrogen. Modeling results exemplify the highly nonlinear characteristics of hydrocarbon nitrogen oxides/ozone cycles in the atmosphere and the inherent difficulties in ameliorating the Los Angeles smog problem within federally mandated timetables.
    No preview · Article · Feb 1984 · Journal of Environmental Engineering
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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.
    No preview · Article · Dec 1983 · Environment International
  • T.W. Tesche
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    ABSTRACT: Over the last decade, the development and application of sophisticated atmospheric models that simulate the transport and dispersion of ozone and its precursors have advanced rapidly. Further advancements are most likely to be found in more complete temporal and spatial characterization of photochemical smog formation processes via measurement. This paper provides an overview of the development of atmospheric photochemical dispersion models, first discussing in general terms the various physical processes occurring in the atmosphere that govern the formation, transport, and ultimate fate of ozone. Procedures for representing these physical processes in mathematical terms are presented next. Nearly all of the photochemical models in use today are derived from the semiempirical atmospheric diffusion equation, though theoretical formulations vary depending on which of the various terms in the pollutant mass balance equation are deemed significant for the application at hand. Examples of recent applications of the range of available photochemical model are presented, together with estimates of the accuracy of each generic modeling concept. Several topics warranting future research are identified, including the need to incorporate explicitly more of the stochastic (or probabilistic) nature of the atmosphere into the form of current photochemical model predictions (i.e., estimates of the variance and higher order moments of the predicted concentration distribution).
    No preview · Article · Jan 1983 · Environment International

Publication Stats

532 Citations
42.44 Total Impact Points

Institutions

  • 2006
    • National Center for Atmospheric Research
      Boulder, Colorado, United States
  • 2005-2006
    • The Harvard Drug Group
      Ливония, Michigan, United States
  • 1994
    • Carnegie Mellon University
      • Department of Mechanical Engineering
      Pittsburgh, Pennsylvania, United States