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Effect of aerosols and NO₂ concentration on ultraviolet actinic flux near Mexico City during MILAGRO: Measurements and model calculations


Citation:Palancar, G.G., B.L. Lefer, S.R. Hall (more) , 2013: Effect of aerosols and NO₂ concentration on ultraviolet actinic flux near Mexico City during MILAGRO: Measurements and model calculations. Atmospheric Chemistry and Physics, 13, 1011-1022, DOI: 10.5194/acp-13-1011-2013.
UCAR/NCAR/UCP Authors:
Other Authors:
UCAR Affiliations: Atmospheric Chemistry Division (ACD), NCAR Earth System Laboratory (NESL)
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Abstract:Urban air pollution absorbs and scatters solar ultraviolet (UV) radiation, and thus has a potentially large effect on tropospheric photochemical rates. We present the first detailed comparison between actinic fluxes (AF) in the wavelength range 330-420 nm measured in highly polluted conditions and simulated with the Tropospheric Ultraviolet-Visible (TUV) model. Measurements were made during the MILAGRO campaign near Mexico City in March 2006, at a ground-based station near Mexico City (the T1 supersite) and from the NSF/NCAR C-130 aircraft. At the surface, measured AF values are typically smaller than the model by up to 25% in the morning, 10% at noon, and 40% in the afternoon, for pollution-free and cloud-free conditions. When measurements of PBL height, NO2 concentration and aerosols optical properties are included in the model, the agreement improves to within ±10% in the morning and afternoon, and ±3% at noon. Based on daily averages, aerosols account for 68% and NO2 for 25% of AF reductions observed at the surface. Several overpasses from the C-130 aircraft provided the opportunity to examine the AF perturbations aloft, and also show better agreement with the model when aerosol and NO2 effects are included above and below the flight altitude. TUV model simulations show that the vertical structure of the actinic flux is sensitive to the choice of the aerosol single scattering albedo (SSA) at UV wavelengths. Typically, aerosols enhance AF above the PBL and reduce AF near the surface. View More
Classification:Refereed
Resource Type:Article
Date Published
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  • dx.doi.org/10.5194/acp-13-1011-2013
Published Version:10.5194/acp-13-1011-2013
Copyright Notice:Copyright Author(s) 2013. This work is distributed under the Creative Commons Attribution 3.0 License
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mexico effect chemistry actinic milagro
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