AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Zero Temperature Gradient Operation of a CCN Counter in SFCA Mode
SARA PURDUE, Jack J. Lin, Athanasios Nenes, Tomi Raatikainen, Greg Kok, Georgia Institute of Technology
Abstract Number: 656 Working Group: Instrumentation and Methods
Abstract The Droplet Measurement Technologies Continuous Flow Streamwise Thermal Gradient Cloud Condensation Nuclei (CCN) Counter is an instrument widely used to study CCN and hygroscopicity properties of aerosols. Under its normal mode of operation supersaturation is generated by a creating a linear temperature gradient along a wetted column$^1. However, when the instrument is operated in the Scanning Flow CCN Analysis (SFCA) mode, supersaturation is generated by changing the flow rate over a short period of time, creating transient pressure fluctuations within the column$^2. Previously, some work has looked at the capabilities of this method while there is still a temperature gradient in the column$^3 but the use of the CCN counter with a zero temperature gradient along the column while in SFCA mode has yet to be studied in laboratory experiments.
This work will provide a first look at the capabilities of the DMT CCN counter with a zero temperature gradient along the column while in SFCA mode. We have run experiments with inlet pressures from 600 to 900mb, scan times from 20 to 60 seconds, and total column temperatures from 25$^oC to 35$^oC. We will present the effect that these variables have on the supersaturation generated in the column, as well as offer a recommendation for the best operating procedure when using the instrument with a zero temperature gradient. Furthermore, the work in this project will be used in the development of a smaller version of the current CCN counter, which can more easily and cost-effectively be deployed in the field and on aircraft.
1. Roberts and Nenes, Aerosol Sci. Tech., 2005
2. Raatikainen et al., Aerosol Sci. Tech., 2014
3. Moore and Nenes, Aerosol Sci. Tech., 2009