Abstract
Abstract. Large uncertainties exist in global climate model predictions of radiative forcing due to insufficient understanding and simplified numerical representation of cloud formation and cloud–aerosol interactions. The Holistic Interactions of Shallow Clouds, Aerosols and Land Ecosystems (HI-SCALE) campaign was conducted near the DOE's Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in north-central Oklahoma to provide a better understanding of land–atmosphere interactions, aerosol and cloud properties, and the influence of aerosol and land–atmosphere interactions on cloud formation. The HI-SCALE campaign consisted of two intensive observational periods (IOPs) (April–May and August–September, 2016), during which coincident measurements were conducted both on the G-1 aircraft platform and at the SGP ground site. In this study we focus on the observations at the SGP ground site. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and an Ionicon proton-transfer-reaction mass spectrometer (PTR-MS) were deployed, characterizing chemistry of non-refractory aerosol and trace gases, respectively. Contributions from various aerosol sources, including biogenic and biomass burning emissions, were retrieved using factor analysis of the AMS data. In general, the organic aerosols at the SGP site was highly oxidized, with oxygenated organic aerosol (OOA) identified as the dominant factor for both the spring and summer IOP though more aged in spring. Cases of isoprene-epoxydiol-derived secondary organic aerosol (IEPOX SOA) and biomass burning events were further investigated to understand additional sources of organic aerosol. Unlike other regions largely impacted by IEPOX chemistry, the IEPOX SOA at SGP was more highly oxygenated, likely due to the relatively weak local emissions of isoprene. Biogenic emissions appear to largely control the formation of organic aerosol (OA) during the HI-SCALE campaign. Potential HOM (highly oxygenated molecule) chemistry likely contributes to the highly oxygenated feature of aerosols at the SGP site, with impacts on new particle formation and global climate.
Highlights
Atmospheric aerosols have been the subject of intensive ongoing research due to their important impacts on the climate
The back trajectories suggested that the air masses arriving at the Southern Great Plains (SGP) site mainly originated from the north during first half of the intensive observational periods (IOPs) and gradually transitioned to originating from the south
Observations of gas-phase volatile organic compounds (VOCs) and particle-phase chemical composition were taken at the SGP site during the HISCALE campaign in 2016, with two intensive operation periods covering the spring and summer season
Summary
Atmospheric aerosols have been the subject of intensive ongoing research due to their important impacts on the climate. There are large uncertainties associated with cloud–aerosol interactions in global climate models (Fan et al, 2016), partly due to insufficient coincident data that couple cloud macrophysical and microphysical properties to aerosol properties. These studies demonstrate that colocated measurements of meteorology, radiation, aerosols, and clouds are needed to evaluate treatments of aerosol pro-. Surface processes involving land–atmosphere interactions have potential impacts on aerosol properties, which influences cloud formation To address these knowledge gaps, the Holistic Interactions of Shallow Clouds, Aerosols and Land Ecosystems (HI-SCALE) campaign was conducted near the DOE’s Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in north-central Oklahoma in 2016
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