Toward understanding atmospheric physics impacting the relationship between columnar aerosol optical depth and near-surface PM2.5 mass concentrations in Nevada and California, U.S.A., during 2013. (December 2017)

• Record Type: Journal Article
• Authors: Loría-Salazar, S. Marcela; Panorska, Anna; Arnott, W. Patrick; Barnard, James C.; Boehmler, Jayne M.; Holmes, Heather A.
• Is Part Of: Atmospheric environment. Volume 171(2017)
• Page Start: 289
• Page End: 300
• Publication Date: 2017-12
• Subjects: Apparent aerosol optical height -- Aerosol transport -- Aerosol vertical profile -- Particulate matter -- Columnar aerosol -- Aerosol physics; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2017.10.023
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: Determining the relationship between columnar aerosol optical depth ( τ ext ) and surface particulate matter concentrations ( PM 2.5 ) is desired to estimate surface aerosol concentrations over broad spatial and temporal scales using satellite remote sensing. However, remote sensing studies incur challenges when surface aerosol pollution (i.e. PM 2.5 ) is not correlated with columnar conditions (i.e., τ ext ). PM 2.5 data fusion models that rely on satellite data and statistical relationships of τ ext and PM 2.5 may not be able to capture the physical conditions impacting the relationships that cause columnar and surface aerosols to not be correlated in the western U.S. Therefore, an extensive examination of the atmospheric conditions is required to improve surface estimates of PM 2.5 that rely on columnar aerosol measurements. This investigation uses datasets from both routine monitoring networks and models of meteorological variables and aerosol physical parameters to understand the atmospheric conditions under which surface aerosol pollution can be explained by column measurements in California and Nevada during 2013. A novel quadrant method, that utilizes statistical analysis, was developed to investigate the relationship between τ ext and PM 2.5 . The results from this investigation show that τ ext and PM 2.5 had a positive association ( τ ext and PM 2.5 increase together) when local sources of pollution or wildfires dominated aerosol pollution in the presence of a deep and well-mixed planetary boundary layer (PBL). Moreover, τ ext and PM 2.5 had no association (where the variables are not related) when stable conditions, long-range transport, or entrainment of air from above the PBL were observed. It was found that seasonal categorization of the relationship between τ ext and PM 2.5, an approach commonly used in statistical models to estimate surface concentrations with satellite remote sensing, may not be enough to account for the atmospheric conditions that drive the relationships between τ ext and PM 2.5 . For all stations, winter showed the maximum average PM 2.5 concentrations (14.1 μg m −3, σ = 11.6 μg m −3 ) meanwhile, τ ext reached minimum values (0.06 μg m −3, σ = 0.04) during the same season. Conversely, spring presented the minimum average PM 2.5 concentrations (9.4 μg m −3, σ = 6.9 μg m −3 ) and the average values of τ ext during spring had the second highest values (0.11, σ = 0.06) averaged for all stations. Highlights: Multiple relationships between τ ext and PM 2.5 in California and Nevada. Atmospheric processes affect the relationship between τ ext and PM 2.5 . Quadrant method diagnoses atmospheric processes impacting τ ext and PM 2.5 . Local pollution sources in a well-mixed PBL leads to positive association. Stable PBL and long-range transport results in no association.