Two-Column Aerosol Project: Impact of Elevated Particle Layers on Particle Optical Depth

Scientists gain insights into aerosol properties near the North American coast.

The Science

Key knowledge gaps persist in the scientific understanding of how aerosol particles and clouds evolve and affect climate. A recent study near Cape Cod highlighted the impact of airborne aerosol layers on the amount of sunlight reaching Earth’s surface.

The Impact

Data collected during the Two-Column Aerosol Project (TCAP) better represent the importance of accounting for mixtures of different compounds in atmospheric particles and how these mixtures affect aerosol particle optical properties over a deep layer of the atmosphere where human-caused effects are expected to be the largest, as well as in a geographic area where model uncertainties are a significant concern.


TCAP was designed to provide a detailed set of observations to tackle an area of unknowns about aerosol particle optical properties in an area where human-caused effects are present. A team of researchers led by Department of Energy (DOE) scientists at Pacific Northwest National Laboratory (PNNL) organized a year-long deployment of the Atmospheric Radiation Measurement (ARM) Mobile Facility to Cape Cod, Massachusetts, for the 12-month duration of the TCAP project. The surface measurements were augmented by two separate one-month long deployments of the ARM Aerial Facility (AAF), one in the summer and one in winter. Few datasets currently combine the range of detailed measurements like those made during TCAP over a range of seasons; in particular, measurements to examine the chemical composition of aerosol particles, their optical properties, and their ability to act as seeds for cloud drops. Using the AFF data, the team found that elevated layers of aerosols occurred on four of six cloud-free days sampled during the summer deployment period. These layers, with increased amounts of biomass burning material and nitrate compared to aerosol at other altitudes, have a large impact on the amount of sunlight reaching Earth’s surface. This TCAP data will be used to better constrain regional and global models.

Principal Investigator(s)

Larry Berg
Pacific Northwest National Laboratory


This research was supported by the National Oceanic and Atmospheric Adminstration’s GOES-R Cal/Val Activities within the National Environmental Satellite, Data, and Information Service; DOE Office of Science, Office of Biological and Environmental Research, ARM and Atmospheric System Research programs (DE-SC0006080). PNNL is operated by DOE by the Battelle Memorial Institute under contract DE-A06-76RLO 1830.


Berg, L. K., J. D. Fast, J. C. Barnard, S. P. Burton, B. Cairns, D. Chand, J. Comstock, S. Dunagan, R. Ferrare, C. Flynn, J. Hair, C. Hostetler, J. Hubbe, A. Jefferson, R. Johnson, E. Kassianov, C. Kluzek, P. Kollias, K. Lamer, K. Lantz, F. Mei, M. Miller, J. Michalsky, I. Ortega, M. Pekour, R. Rogers, P. Russell, J. Redemann, A. Sedlacek, M. Segal-Rosenheimer, B. Schmid, J. Shilling, Y. Shinokuza, S. Springston, J. Tomlinson, M. Tyrell, J. Wilson, R. Volkamer, A. Zelenyuk, and C. Berkowitz. 2016. “The Two-Column Aerosol Project: Phase I Overview and Impact of Elevated Aerosol Layers on Aerosol Optical Depth,” Journal of Geophysical Research: Atmospheres 121(1), 336–61. DOI: 10.1002/2015JD023848.