Ground-based High Spectral Resolution Lidar observation of aerosol vertical distribution in the summertime Southeast United States
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Date
2017
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Citation of Original Publication
Reid, Jeffrey S., Ralph E. Kuehn, Robert E. Holz, Edwin W. Eloranta, Kathleen C. Kaku, Shi Kuang, Michael J. Newchurch, et al. “Ground-Based High Spectral Resolution Lidar Observation of Aerosol Vertical Distribution in the Summertime Southeast United States.” Journal of Geophysical Research: Atmospheres 122, no. 5 (2017): 2970–3004. https://doi.org/10.1002/2016JD025798.
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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Public Domain
Abstract
As part of the Southeast United States-based Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC⁴RS), and collinear with part of the Southeast Atmosphere Study, the University of Wisconsin High Spectral Resolution Lidar system was deployed to the University of Alabama from 19 June to 4 November 2013. With a collocated Aerosol Robotic Network (AERONET) sun photometer, a nearby Chemical Speciation Network (PM₂.₅) measurement station, and near daily ozonesonde releases for the August–September SEAC⁴RS campaign, the site allowed the region's first comprehensive diurnal monitoring of aerosol particle vertical structure. A 532 nm lidar ratio of 55 sr provided good closure between aerosol backscatter and AERONET (aerosol optical thickness, AOT). A principle component analysis was performed to identify key modes of variability in aerosol backscatter. “Fair weather” days exhibited classic planetary boundary layer structure of a mixed layer accounting for ~50% of AOT and an entrainment zone providing another 25%. An additional 5–15% of variance is gained from the lower free troposphere from either convective detrainment or frequent intrusions of western United States biomass burning smoke. Generally, aerosol particles were contained below the 0°C level, a common level of stability in convective regimes. However, occasional strong injections of smoke to the upper troposphere were also observed, accounting for the remaining 10–15% variability in AOT. Examples of these common modes of variability in frontal and convective regimes are presented, demonstrating why AOT often has only a weak relationship to surface PM₂.₅ concentration.