Aerosol Hygroscopicity Kappa Data Product Available for Evaluation

Published: 20 April 2021

At ARM's Southern Great Plains atmospheric observatory, kappa values within critical diameter-supersaturation field space, top, and a time series of kappa, bottom
Sample plots from ARM’s Southern Great Plains atmospheric observatory show kappa values within critical diameter-supersaturation field space, top, and a time series of kappa, bottom.

A new value-added product (VAP) from the Atmospheric Radiation Measurement (ARM) user facility calculates the hygroscopic properties of measured aerosol particles. Hygroscopicity is the ability of a particle to take up moisture from the environment and is important for understanding the formation of cloud condensation nuclei (CCN). Users can now evaluate this VAP, called CCN Counter and Scanning Mobility Particle Sizer (SMPS) Derived Hygroscopicity Parameter Kappa (CCNSMPSKAPPA).

The hygroscopicity parameter, kappa, quantifies a particle’s capacity to activate into a water droplet. This kappa product provides a means to quantify hygroscopic properties of ambient aerosols and could be used to evaluate aerosol properties simulated in global earth system models.

The ARM CCN particle counter measures the fraction of ambient aerosols that can become liquid droplets at five supersaturations. These CCN and co-located dry aerosol particle size measurements from the SMPS are used to calculate the critical diameter—the minimum particle diameter required to activate into a water droplet. For each critical diameter value, kappa is calculated using the kappa-Köhler theory (Petters and Kreidenweis 2007).

The first CCNSMPSKAPPA data are from April 12, 2017, to February 5, 2021, for the ARM Southern Great Plains E13 site near Lamont, Oklahoma.

Scientists can use the aerosol hygroscopicity kappa VAP to help improve the understanding of aerosol-cloud interaction treatment in global earth system models. Future work will involve expanding the availability of this product at more ARM sites where CCN particle counter and SMPS data are available.

To learn more about this product, go to the VAP web page.

If you have questions or feedback to help improve this evaluation product, please contact data scientist Gourihar Kulkarni, ARM translator John Shilling, or VAP developer Maxwell Levin.

Data can be referenced as doi:10.5439/1729907. Access the data set in the ARM Data Center. (Go here to create an account to download the data.)

Reference: Petters MD and SM Kreidenweis. 2007. “A single parameter representation of hygroscopic growth and cloud condensation nucleus activity.” Atmospheric Chemistry and Physics, 7, 1961–1971,

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