Aerosol–Cloud Interactions Observed during the Holistic Interactions of Shallow Clouds, Aerosols, and Land Ecosystems (HI-SCALE) Campaign (Invited Presentation)

The Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) campaign was conducted recently in May and September of 2016 near the DOE’s Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site located in Oklahoma. The goal of the HI-SCALE campaign is to provide a detailed set of aircraft and surface measurements needed to obtain a more complete understanding and improved parameterizations of the lifecycle of shallow clouds. The aircraft flight sampling included transects in the middle boundary layer, below clouds, within clouds, and above clouds. While the SGP site is in a rural environment, it is impacted by anthropogenic, biogenic, and biomass burning sources of aerosols and their precursors. The relative contribution of anthropogenic, biogenic, and biomass burning aerosols was found to vary significantly from day to day. Plumes of sulfur dioxide and sulfate originating from a power plant and a few refineries near the SGP site were also frequently observed by the aircraft. We characterize the spatial variability of aerosol concentration, composition, and size that influence cloud condensation nuclei (CCN) in relation to the population of shallow clouds. We also investigate the role of aerosols on cloud properties of shallow clouds, such as droplet size and aqueous chemistry. Observations indicate aqueous phase organic chemistry occurs frequently in shallow clouds in the vicinity of the SGP site. Ultimately, these observations will be used to evaluate model treatments of cloud-aerosol interactions used by microphysics (resolved cloud) and convection (unresolved cloud) parameterizations.