Clean Air Corridors: A Geographic and

Green, Mark C.; Gebhart, Kristi A.

doi:10.1080/10473289.1997.10464442

Cited by 5 publications

(5 citation statements)

References 6 publications

(4 reference statements)

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“…In addition to encouraging new mobile source standards, renewable power generation technology, and lower emitting practices for prescribed fires, many of the recommendations were for better emission estimation and tracking methods. Clean air corridors [141][142][143] were defined as upwind areas with low emissions, large amounts of dilution, or higher amounts of pollutant removal. Clean air corridors identified in central Nevada, eastern Utah, eastern Oregon, and western Idaho were given the same status as other locations-as long as new emissions would not add to perceptible b ext above natural levels, development could continue to the north of the Grand Canyon and nearby Class I areas.…”

Section: Regional Haze Rulementioning

confidence: 99%

“…Malm 23 showed several examples of how average trajectories can be used to estimate the frequency of air mass transport throughout the year and to associate potential source regions with the highest SO 4 2concentrations. Green and Gebhart 143 showed how trajectories were used to define the clean air corridors considered by the GCVTC. These modeling analyses might be used to define regions within which emission caps could be applied.…”

Section: Mixing and Transportmentioning

confidence: 99%

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Visibility: Science and Regulation

Watson

2002

Journal of the Air & Waste Management Association

932

548

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The 1999 Regional Haze Rule provides a context for this review of visibility, the science that describes it, and the use of that science in regulatory guidance. The scientific basis for the 1999 regulation is adequate. The deciview metric that tracks progress is an imperfect but objective measure of what people see near the prevailing visual range. The definition of natural visibility conditions is adequate for current planning, but it will need to be refined as visibility improves. Emissions from other countries will set achievable levels above those produced by natural sources. Some natural events, notably dust storms and wildfires, are episodic and cannot be represented by annual average background values or emission estimates. Sulfur dioxide (SO2) emission reductions correspond with lower sulfate (SO4(2-)) concentrations and visibility improvements in the regions where these have occurred. Non-road emissions have been growing more rapidly than emissions from other sources, which have remained stable or decreased since 1970. Simpler models representing transport, limiting precursor pollutants, and gas-to-particle equilibrium should be used to understand where and when emission reductions will be effective, rather than large complex models that have insufficient input and validation measurements. Examples of model-based source attribution show large differences among estimates from various modeling systems and with ambient measurements.

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Section: Regional Haze Rulementioning

confidence: 99%

Section: Mixing and Transportmentioning

confidence: 99%

Visibility: Science and Regulation

Watson

2002

Journal of the Air & Waste Management Association

932

548

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“…Low pressures in the Colorado Plateaus Basin or high pressures west of the canyon will cause air to flow eastward through the canyon. Pollutants during these events may come from Las Vegas, the Los Angeles Basin, or from other regional sources west of the canyon (Stauffer and Seaman 1994;Green and Gebhart 1997).…”

Section: Winds Within the Grand Canyonmentioning

confidence: 99%

Wintertime Boundary Layer Structure in the Grand Canyon

Whiteman¹,

Zhong²,

Bian³

1999

J. Appl. Meteor.

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Wintertime temperature profiles in the Grand Canyon exhibit a neutral to isothermal stratification during both daytime and nighttime, with only rare instances of actual temperature inversions. The canyon warms during daytime and cools during nighttime more or less uniformly through the canyon's entire depth. This weak stability and temperature structure evolution differ from other Rocky Mountain valleys, which develop strong nocturnal inversions and exhibit convective and stable boundary layers that grow upward from the valley floor. Mechanisms that may be responsible for the different behavior of the Grand Canyon are discussed, including the possibility that the canyon atmosphere is frequently mixed to near-neutral stratification when cold air drains into the top of the canyon from the nearby snow-covered Kaibab Plateau. Another feature of canyon temperature profiles is the sharp inversions that often form near the canyon rims. These are generally produced when warm air is advected over the canyon in advance of passing synoptic-scale ridges. Wintertime winds in the main canyon are not classical diurnal along-valley wind systems. Rather, they are driven along the canyon axis by the horizontal synoptic-scale pressure gradient that is superimposed along the canyon's axis by passing synoptic-scale weather disturbances. They may thus bring winds into the canyon from either end at any time of day. The implications of the observed canyon boundary layer structure for air pollution dispersion are discussed.

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“…A major component of this assessment used the Visibility and Haze in the Western Atmosphere (VISHWA) air quality model 1 to predict the impacts upon visibility of various sources under current and projected emissions scenarios. The analysis of clean air corridors 2,3 (areas supplying clean air to GCNP) relied heavily upon a trajectory model. 4 Satisfactory results from both models are highly dependent upon the winds used by the model.…”

Section: Discussionmentioning

confidence: 99%

“…The ATAD model has been used by many researchers to compute forward and backward air trajectories 2,10,11,12 using wind data from the national network of radiosonde stations. Because the model requires little computational time, a large number of trajectories can be run for statistical analyses.…”

Section: Atadmentioning

confidence: 99%

Evaluation of Wind Fields Used in Grand Canyon Visibility Transport Commission Analyses

Green

Pai

Ashbaugh

et al. 2000

Journal of the Air & Waste Management Association

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The Grand Canyon Visibility Transport Commission (GCVTC) was established by the U.S. Congress to assess the potential impacts of projected growth on atmospheric visibility at Grand Canyon National Park and to make recommendations to the U.S. Environmental Protection Agency on what measures could be taken to avoid such adverse impacts. A critical input to the assessment tool used by the commission was three-dimensional modelderived wind fields used to transport the emissions. This paper describes the evaluation of the wind fields used at various stages in the assessment. Wind fields evaluated included those obtained from the Colorado State University Regional Atmospheric Modeling System (RAMS), the National Meteorological Center's Nested Grid Model (NGM), and the National Oceanic and Atmospheric Administration's Atmospheric Transport and Dispersion (ATAD) trajectory model. The model-derived wind fields were evaluated at multiple vertical levels at several locations in the southwestern United States by determining IMPLICATIONS Model winds used for the Grand Canyon Visibility Transport Commission assessment were not in good agreement with measured winds. The poor performance of the wind field models adds significant uncertainty to the quantification of source-receptor relationships used in the GCVTC assessment. Until wind fields are improved, considerable caution must be used when considering the results of air quality models in the highly complex terrain of the southwestern United States. differences between model predicted winds and winds that were measured using radiosonde and radar wind profiler data. Model-derived winds were also evaluated by determining the percent of time that they were within acceptable differences from measured winds.All models had difficulties, generally meeting the acceptable criteria for less than 50% of the predictions. The RAMS model had a persistent bias toward southwesterly winds at the expense of other directions, especially failing to represent channeling by north-south mountain ranges in the lower levels. The NGM model exhibited a substantial bias in the summer months by extending northwesterly winds in the eastern Pacific Ocean well inland, in contrast to the observed southwesterlies at inland locations. The simpler ATAD trajectory model performed somewhat better than the other models, probably because of its use of more upper air sites. The results of the evaluation indicated that these wind fields could not be used to reliably predict source-receptor impacts on a particular day; thus, seasonally averaged impacts were used in the GCVTC assessment.

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Clean Air Corridors: A Geographic and

Cited by 5 publications

References 6 publications

Visibility: Science and Regulation

Visibility: Science and Regulation

Wintertime Boundary Layer Structure in the Grand Canyon

Evaluation of Wind Fields Used in Grand Canyon Visibility Transport Commission Analyses

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