Development of an improved image processing based visibility model

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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“…Contrast transmittance: Photographs and time-lapse film 189,191,198,[246][247][248][249][250] Particle scattering (b scat,p ):…”

Section: -244mentioning

confidence: 99%

Visibility: Science and Regulation

Watson

2002

Journal of the Air & Waste Management Association

936

548

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“…The complex mixture of chemical substances present in particles of a given size is then represented as an external mixture of the appropriate number of distinctly different particle types. The method of calculating refractive indices and light scattering that is described in this paper has been discussed previously by Larson et al [1988] and Eldering et al [1994, 1993]. Eldering et al [1993] demonstrated that skylight radiances calculated by these methods compare well to those measured independently with a radiometer.…”

Section: Model Descriptionmentioning

confidence: 99%

Aerosol optical properties during INDOEX based on measured aerosol particle size and composition

Eldering

Ogren²,

Chowdhury

et al. 2002

J.‐Geophys.‐Res.

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[1] The light scattering and light absorption as a function of wavelength and relative humidity due to aerosols measured at the Kaashidhoo Climate Observatory in the Republic of the Maldives during the INDOEX field campaign has been calculated. Using sizesegregated measurements of aerosol chemical composition, calculated light scattering and absorption has been evaluated against measurements of light scattering and absorption. Light scattering coefficients are predicted to within a few percent over relative humidities of 20-90%. Single scattering albedos calculated from the measured elemental carbon size distributions and concentrations in conjunction with other aerosol species have a relative error of 4.0% when compared to measured values. The single scattering albedo for the aerosols measured during INDOEX is both predicted and observed to be about 0.86 at an ambient relative humidity of 80%. These results demonstrate that the light scattering, light absorption, and hence climate forcing due to aerosols over the Indian Ocean are consistent with the chemical and physical properties of the aerosol at that location.

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“…image processing-based visibility models[Eldering et al, 1993] that can produce synthetic color photographs of the appearance of the surrounding landscape as it would be seen from inside the air parcel in those cases where the visual range Lv is comparable to the dimensions of the air parcels tracked by a trajectory model (i.e., when Lv is less than or equal to several kilometers).…”

mentioning

confidence: 99%

Source‐oriented model for air pollutant effects on visibility

Eldering¹,

Cass²

1996

J. Geophys. Res.

123

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Abstract. A source-oriented model for air pollutant effects on visibility has been developed that can compute light scattering, light extinction, and estimated visual range directly from data on gas phase and primary particle phase air pollutant emissions from sources. The importance of such a model is that it can be used to compute the effect of emission control proposals on visibility-related parameters in advance of the adoption of such control programs. The model has been assembled by embedding several aerosol process modules within the photochemical trajectory model previously developed for aerosol nitrate concentration predictions by Russell et al. [1983] and Russell and Cass [1986]. These modules describe the size distribution and chemical composition of primary particle emissions, the speciation of organic vapor emissions, atmospheric chemical reactions, transport of condensible material between the gas and the particle phases, fog chemistry, dry deposition, and atmospheric light scattering and light absorption.

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Development of an improved image processing based visibility model

Cited by 38 publications

References 13 publications

Visibility: Science and Regulation

Visibility: Science and Regulation

Aerosol optical properties during INDOEX based on measured aerosol particle size and composition

Source‐oriented model for air pollutant effects on visibility

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