Formation and Transport of Secondary Air Pollutants: Ozone and Aerosols in the St. Louis Urban Plume

White, WH; Anderson, J.; Blumenthal, D.L.; Husar, R.B.; Gillani, Noor V.; Husar, J.D.; Wilson, William E.

doi:10.1126/science.959846

Cited by 171 publications

(117 citation statements)

References 7 publications

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“…4: there is an obvious peak at the mean flight loop frequency (usually ∼ 100 s period) followed by a smaller negative dip at higher frequencies within the meandering effluent plume. We believe this to be good evidence that our method captures this important component of the overall flux away from the source, which cannot be obtained with a traditional mean wind and an integrated concentration enhancement measurement that is so often employed in airborne source estimates (Ryerson et al, 2001;White et al, 1976).…”

Section: The Upwind-directed Turbulent Fluxmentioning

confidence: 91%

Application of Gauss's theorem to quantify localized surface emissions from airborne measurements of wind and trace gases

et al. 2017

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Abstract. Airborne estimates of greenhouse gas emissions are becoming more prevalent with the advent of rapid commercial development of trace gas instrumentation featuring increased measurement accuracy, precision, and frequency, and the swelling interest in the verification of current emission inventories. Multiple airborne studies have indicated that emission inventories may underestimate some hydrocarbon emission sources in US oil-and gas-producing basins. Consequently, a proper assessment of the accuracy of these airborne methods is crucial to interpreting the meaning of such discrepancies. We present a new method of sampling surface sources of any trace gas for which fast and precise measurements can be made and apply it to methane, ethane, and carbon dioxide on spatial scales of ∼ 1000 m, where consecutive loops are flown around a targeted source region at multiple altitudes. Using Reynolds decomposition for the scalar concentrations, along with Gauss's theorem, we show that the method accurately accounts for the smallerscale turbulent dispersion of the local plume, which is often ignored in other average "mass balance" methods. With the help of large eddy simulations (LES) we further show how the circling radius can be optimized for the micrometeorological conditions encountered during any flight. Furthermore, by sampling controlled releases of methane and ethane on the ground we can ascertain that the accuracy of the method, in appropriate meteorological conditions, is often better than 10 %, with limits of detection below 5 kg h −1 for both methane and ethane. Because of the FAA-mandated minimum flight safe altitude of 150 m, placement of the aircraft is critical to preventing a large portion of the emission plume from flowing underneath the lowest aircraft sampling altitude, which is generally the leading source of uncertainty in these measurements. Finally, we show how the accuracy of the method is strongly dependent on the number of sampling loops and/or time spent sampling the source plume.

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Section: The Upwind-directed Turbulent Fluxmentioning

confidence: 91%

Application of Gauss's theorem to quantify localized surface emissions from airborne measurements of wind and trace gases

et al. 2017

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“…Mass budget approaches have been employed on several occasions to derive regional-scale (> 1 km) fluxes of trace species (White et al, 1976;Gallagher et al, 1994;Choularton et al, 1995;Wratt et al, 2001;Mays et al, 2009;O'Shea et al, 2014). Observations are typically made in a background location and then down-wind of a source region to determine the net enhancement due to this region.…”

Section: Aircraft Mass Balancementioning

confidence: 99%

Methane and carbon dioxide fluxes and their regional scalability for the European Arctic wetlands during the MAMM project in summer 2012

et al. 2014

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Abstract. Airborne and ground-based measurements of methane (CH 4 ), carbon dioxide (CO 2 ) and boundary layer thermodynamics were recorded over the Fennoscandian landscape (67-69.5 • N, 20-28 • E) in July 2012 as part of the MAMM (Methane and other greenhouse gases in the Arctic: Measurements, process studies and Modelling) field campaign. Employing these airborne measurements and a simple boundary layer box model, net regional-scale (∼ 100 km) fluxes were calculated to be 1.2 ± 0.5 mg CH 4 h −1 m −2 and −350 ± 143 mg CO 2 h −1 m −2 . These airborne fluxes were found to be relatively consistent with seasonally averaged surface chamber (1.3 ± 1.0 mg CH 4 h −1 m −2 ) and eddy covariance (1.3 ± 0.3 mg CH 4 h −1 m −2 and −309 ± 306 mg CO 2 h −1 m −2 ) flux measurements in the local area. The internal consistency of the aircraft-derived fluxes across a wide swath of Fennoscandia coupled with an excellent statistical comparison with local seasonally averaged ground-based measurements demonstrates the potential scalability of such localised measurements to regional-scale representativeness. Comparisons were also made to longerterm regional CH 4 climatologies from the JULES (Joint UK Land Environment Simulator) and HYBRID8 land surface models within the area of the MAMM campaign. The average hourly emission flux output for the summer period Based on these observations both models were found to significantly underestimate the CH 4 emission flux in this region, which was linked to the under-prediction of the wetland extents generated by the models.

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“…Other meteorological conditions such as persistent winds causing long range transport aloft also contribute to elevated oxidant episodes. 15 ' 16 The number of stagnations during the May through October period varied considerably from year to year. 10 From as little as one stagnation of 5 days duration to as many as 10 stagnations covering a total of 57 days can occur in any one year with a 40 yr average of 5 stagnations over a total of 28 days/yr.…”

Section: Resultsmentioning

confidence: 99%

Association of Oxidant Episodes with Warm Stagnating Anticyclones

Altshuiler¹

1978

Journal of the Air Pollution Control Association

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Formation and Transport of Secondary Air Pollutants: Ozone and Aerosols in the St. Louis Urban Plume

Cited by 171 publications

References 7 publications

Application of Gauss's theorem to quantify localized surface emissions from airborne measurements of wind and trace gases

Application of Gauss's theorem to quantify localized surface emissions from airborne measurements of wind and trace gases

Methane and carbon dioxide fluxes and their regional scalability for the European Arctic wetlands during the MAMM project in summer 2012

Association of Oxidant Episodes with Warm Stagnating Anticyclones

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