Field observations of regional and urban impacts on NO2, ozone, UVB, and nitrate radical production rates in the Phoenix air basin

Gaffney, J. S.; Marley, N. A.; Drayton, P. J.; Doskey, Paul V.; Kotamarthi, V. R.; Cunningham, Mary M.; Baird, J. C.; Dintaman, J.; Hart, Heather L.

doi:10.1016/s1352-2310(01)00528-3

Cited by 28 publications

(31 citation statements)

References 32 publications

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“…This is in contrast to previous measurements obtained at Usery Pass, at a site on the eastern (downwind) side of the city of Phoenix, in MayJune 1998; here, O 3 levels were as high as 95 ppb and exceeded 80 ppb on a number of days. 25 O 3 values are seen to reach maximum values during the early afternoon at both sites consistent with local photochemical sources. Nighttime O 3 values are when min values are found and are consistent with O 3 loss because of titration by NO to form NO 2 being the predominant loss mechanism followed by O 3 dry deposition to the surface.…”

Section: Resultssupporting

confidence: 59%

Beryllium-7 Measurements in the Houston and Phoenix Urban Areas: An Estimation of Upper Atmospheric Ozone Contributions

Gaffney

Marley

Cunningham

et al. 2005

Journal of the Air & Waste Management Association

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Section: Resultssupporting

confidence: 59%

Beryllium-7 Measurements in the Houston and Phoenix Urban Areas: An Estimation of Upper Atmospheric Ozone Contributions

Gaffney

Marley

Cunningham

et al. 2005

Journal of the Air & Waste Management Association

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“…10 for days without rain events. Both sites show reduced UVB radiation when compared to the clear sky modeled values, as expected for sites with significant UVB absorbing gases and aerosols (Castro et al, 2001;Gaffney et al, 2002;Barnard et al, 2008). However, the UVB radiation field observed at site T1 is reduced further than that observed at site T0.…”

Section: MMsupporting

confidence: 55%

Measurements of aerosol absorption and scattering in the Mexico City Metropolitan Area during the MILAGRO field campaign: a comparison of results from the T0 and T1 sites

Marley

Gaffney

Castro³

et al. 2009

Atmos. Chem. Phys.

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Abstract. In March 2006, a multiagency field campaign was undertaken in Mexico City called the Megacities Initiative: Local and Global Research Observations (MILAGRO). Two of the five field components of the MILAGRO study focused a major part of their efforts on atmospheric particulate emissions from the Mexico City basin and their effects on radiative balance as a function of time, location and processing conditions. As part of these two MILAGRO components, measurements of aerosol optical properties were obtained at a site located in the northern part of Mexico City (T0) and also at a site located 29 km northwest (T1) to estimate the regional effects of aerosol emissions from the basin.Measurements of aerosol absorption and scattering for fine mode aerosols were obtained at both sites. Aerosol absorption at 550 nm was similar at both sites, ranging from 7-107 Mm −1 at T0 and from 3-147 Mm −1 at T1. Aerosol scattering measured at 550 nm at T0 ranged from 16-344 Mm −1 while the aerosol scattering values at T1 were much lower than at T0 ranging from 2-136 Mm −1 . Aerosol single scattering albedos (SSAs) were calculated at 550 nm for the fine mode aerosols at both sites using these data. The SSAs at T0 ranged from 0.47-0.92 while SSAs at T1 ranged from 0.35-Correspondence to: J. S. Gaffney (jsgaffney@ualr.edu) 0.86. The presence of these highly absorbing fine aerosols in the lower atmosphere of the Mexico City area will result in a positive climate forcing and a local warming of the boundary layer in the region.Broadband UVB intensity was found to be higher at site T0, with an average of 64 µW/cm 2 at solar noon, than at site T1, which had an average of 54 µW/cm 2 at solar noon. Comparisons of clear-sky modeled UVB intensities with the simultaneous UVB measurements obtained at sites T0 and T1 for cloudless days indicate a larger diffuse radiation field at site T0 than at site T1. The determination of aerosolÅngstrom scattering coefficients at T0 suggests that this is due to the predominance of aerosols in the size range of 0.3 micron, which leads to scattering of UVB radiation peaked in the forward direction and to an enhanced UVB radiation observed at ground level. This enhancement of the UVB diffuse radiation field would explain the enhanced photochemistry observed in the Mexico City area despite the reduction in UVB anticipated from light absorbing species.

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“…10 for days without rain events. Both sites show reduced UVB radiation when compared to the clear sky modeled values, as expected for sites with significant UVB absorbing gases and aerosols Gaffney et al, 2002;. However, the UVB radiation field observed at site Tl is reduced further than that observed at site TO.…”

Section: Resultssupporting

confidence: 56%

Aerosol Absorption and Scattering Measurements: Field Measuremnets and Laboratory Characterizations.

Marley¹,

Gaffney²

2011

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A suite of instrumentation was deployed in MAX-Mex at site TO, located in the northern part of the Mexico City Metropolitan Area, (MCMA), for the characterization of the aerosol optical properties in the field. Measurements were made of the following aerosol properties: (1) aerosol absorption as a function of wavelength, measured at two minute intervals with a 7-wavelength Aethalometer (2) aerosol scattering as a function of wavelength, measured at one minute intervals with a 3-wavelength nephelometer; 3) aerosol scattering as a function of relative humidity (RH), measured at one minute intervals with 2 single-wavelength nephelometers operated under dry (10% RH) and wet (80% RH) conditions; and 4) collection of sizefractionated aerosol samples on quartz fiber filters at 12 hour intervals (day/night) for further laboratory characterization. Aerosol filter samples were also collected at site Tl (located north of MCMA) for comparison with those collected in the city center. Preliminary results from in situ measurements have indicated an enhanced UV absorption in the afternoon over that expected from black carbon (BC) aerosols alone. These results are directly applicable to both modeling of aerosol radiative forcing and satellite optical depth retrieval algorithms. Both of these applications assume that the aerosol absorption is due only to BC with a wavelength dependence of A, " whereas results obtained in MAX-Mex show that the aerosol wavelength exponent varies over Mexico City from -0.7 to -1.5.All of the data collected in the field from the measurement sets 1-3 have been made available to the ASP community via the MILAGRO data site housed at NCAR. The laboratory characterization of aerosol samples collected in the ASP MAX-Mex field study compared results from Mexico City to samples collected at other sites, including Chicago, Little Rock, and Mt. Bachelor, OR. The project focused on obtaining complete spectral characterization of aerosolsespecially their absorption characteristics as they relate to basic chemical functional groups. Particular attention was given to organics and from biogenic derived organic compounds. This included determinations of the UV-Visible-NIR characteristics of the aerosol absorption as reported as Angstrom Absorption Exponents. Correlation of these results with IR band observations of carboxylic acid, and carboxylate groups were conducted, along with past correlations with carbon isotopic data that indicated significant enhancements of UV-Visible absorption from biogenic aerosols (both biomass burning and secondary organic aerosols). Relationships to other ASP ProjectsThis project collaborated with a number of currently funded ASP projects including research being conducted by Dr. W. Patrick Arnott at the University of Nevada, Reno. Dr. Arnott made use of photoacoustic spectroscopy and light scattering at one or two wavelengths to determine SSA of the aerosol. Comparison of the aethalometer data as well as MAAP instrumentation yielded good to excellent agreement between the instruments...

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Field observations of regional and urban impacts on NO2, ozone, UVB, and nitrate radical production rates in the Phoenix air basin

Cited by 28 publications

References 32 publications

Beryllium-7 Measurements in the Houston and Phoenix Urban Areas: An Estimation of Upper Atmospheric Ozone Contributions

Beryllium-7 Measurements in the Houston and Phoenix Urban Areas: An Estimation of Upper Atmospheric Ozone Contributions

Measurements of aerosol absorption and scattering in the Mexico City Metropolitan Area during the MILAGRO field campaign: a comparison of results from the T0 and T1 sites

Aerosol Absorption and Scattering Measurements: Field Measuremnets and Laboratory Characterizations.

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