Aerosol Hygroscopicity Data Produced for ARM Sites in Alabama, Maryland

Published: 17 November 2025

These sample time-series plots from the CoURAGE field campaign’s rural supplemental site (S2) near Mount Airy, Maryland, on July 2, 2025, show critical diameter, aerosol number concentration, and kappa values by supersaturation setpoint. Plots were generated by Maxwell Levin, Pacific Northwest National Laboratory.

New data are available from a value-added product (VAP) that calculates the hygroscopicity parameter kappa from cloud condensation nuclei (CCN) particle counter and scanning mobility particle sizer (SMPS) measurements collected by the Atmospheric Radiation Measurement (ARM) User Facility.

Production data from the CCN Counter and SMPS Derived Hygroscopicity Parameter Kappa (CCNSMPSKAPPA) VAP are now ready to use for ARM’s Bankhead National Forest (BNF) atmospheric observatory and the ongoing Coast-Urban-Rural Atmospheric Gradient Experiment (CoURAGE). Daily netCDF files are available for the BNF main site in northern Alabama from November 25, 2024, onward, and for CoURAGE’s rural supplemental site (S2) near Mount Airy, Maryland, from February 22, 2025, onward.

Kappa quantifies a particle’s capacity to take up water from the environment and activate into a cloud droplet. Kappa is often used to model the CCN activity of atmospheric aerosols of different sizes and compositions, providing additional insight into the influence of aerosols on atmospheric processes.

The CCNSMPSKAPPA product provides a means to quantify the hygroscopic properties of ambient aerosols. Scientists can use the VAP to help improve the understanding of aerosol-cloud interactions and their representation in global earth system models.

New VAP data are made available when required CCN and SMPS input data become available.

More information about the VAP, including the technical report, can be found on the CCN Counter Derived Hygroscopicity Parameter Kappa (CCNKAPPA) web page. Details on CCNSMPSKAPPA production data released for other ARM sites are available in a previous ARM announcement.

Access the CCNSMPSKAPPA data in the ARM Data Center. (To download the data, first create an ARM account.)

If you have questions or feedback to help improve these data, please contact science mentor Gourihar Kulkarni, ARM translator John Shilling, or VAP developer Maxwell Levin.

Data can be referenced as doi:10.5439/1729907.

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ARM is a DOE Office of Science user facility operated by nine DOE national laboratories.