The Clemson Air Quality Lab deploys instruments for aircraft measurements of atmospheric aerosol particles

October 19, 2018

Assistant Professor Andrew Metcalf and graduate student Walt Williams spent a month during summer 2018 in Monterey, CA working on an aircraft-based field campaign to study the impacts of aerosol particles on cloud formation and local air quality.  The field mission was in collaboration with teams from the Naval Postgraduate School (NPS), Caltech, and the University of Arizona.  The NPS Twin Otter aircraft (pictured below), was outfitted with a suite of aerosol instrumentation to measure the number and size of aerosol particles, aerosol composition and radiative properties, and cloud interaction properties.

The field project, named The Marine Aerosol Cloud And Wildfire Study (MACAWS), aimed to study the impacts of aerosol particles, especially anthropogenic particles from the marine shipping industry, on marine stratocumulus clouds.  Unlike the typically sunny, hot, and humid Clemson area in the summer time, the central coast of California is typically cloudy and cool owing to a daily presence of marine stratocumulus clouds which hug the coast.  The persistence of these clouds provides a good testbed for studying aerosol-cloud interactions, especially in a typically clean marine background.

The figure below shows all of the flight patterns from the MACAWS 2018 study.  The plane is housed in a hangar at the Marina Municipal Airport, several miles north of Monterey.  Flights during this study covered several mission objectives, including tracking shipping emissions, characterizing the background marine environment, and sampling the influences of California wildfires.

Clemson’s participation in the MACAWS project was funded by an NSF RAPID grant #AGS-1833008.  Clemson supplied a Single-Particle Soot Photometer (SP2) to measure refractory black carbon aerosol (which originates from any incomplete combustion source) and a Scanning Electrical Mobility Analyzer (SEMS) to measure total aerosol particle size distributions and number concentrations.  In the photo below, graduate student Walt Williams prepares these instruments on the Twin Otter prior to a research flight.

One of the main goals of the Clemson Air Quality Lab is to understand the interaction of wildfire plumes on local air quality.  To address this goal, the SP2 measures the mass of refractory black carbon aerosol originating from wildfires (like in the picture below) and other combustion sources and whether these particles are coated with any non-refractory substances.  During MACAWS 2018, several large wildfires were sampled, and the team is currently comparing their emissions with the characteristics of background airmasses and shipping emissions encountered during the study.

The results from the MACAWS 2018 study will inform sampling techniques to be employed closer to home, where Metcalf and Williams will study the emissions from prescribed fires in the Clemson Experimental Forest.  Local field deployment is currently planned for winter 2019 for a project supported by South Carolina’s NASA EPSCoR office.  Information collected from field campaigns like these helps increase understanding of how wildfires affect local air quality.  Additionally, this study can be used to quantify the human health effects of controlled burning and can inform future controlled burning decisions based on meteorological conditions.