AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Calibration Uncertainties in Cloud Condensation Nuclei Counters
KURT HIBERT, David Delene, University of North Dakota
Abstract Number: 723 Working Group: Instrumentation and Methods
Abstract Cloud condensation nuclei (CCN) counters have been calibrated regularly for use in field projects and laboratory work for many decades. However, the calibration uncertainties of CCN counters are not well understood. The objective of this research is to determine CCN counter calibration uncertainties for different CCN counters under different conditions. Specifically, the CCN counter's concentration and supersaturation calibration uncertainties are determined for several University of Wyoming (UWyo) and Droplet Measurement Technologies (DMT) CCN counters. Previous research has determined calibration uncertainties for a single supersaturation; however, this project addresses uncertainties over a range of supersaturations, the calibration drift with time, and the dependency of the supersaturation calibration on pressure in the DMT CCN counter. The purpose of analyzing these calibration uncertainties is to determine how well different types of CCN counters agree. In order to determine the calibration uncertainties, the standard deviation is calculated from a series of calibrations on the UWyo and DMT CCN counters. The calibrations made over several years are also evaluated to determine if there is a drift in time. Quantifying the calibration uncertainties allows for accurate comparisons to determine if there are real atmospheric differences in CCN concentration or if differences are a result of different methodology and instrumentation. Preliminary results indicate that the UWyo and DMT CCN counter's concentration calibrations have not drifted over a period of several years. The supersaturation calibrations in the DMT CCN counter have also not drifted with time. DMT CCN counter supersaturation calibrations have been done at reduced pressures and agree with ambient pressure supersaturation calibrations. This research is expected to confirm that measurements made with different CCN counters in different years, and with different calibrations agree within the calculated calibration uncertainties.