A Solution to New Mobility Particle Sizing Instrumentation and CCN Measurement using Scanning Mobility CCN Analysis (SMCA)

Kanishk Gohil, Nahin Ferdousi, AKUA ASA-AWUKU, University of Maryland, College Park

     Abstract Number: 565
     Working Group: Instrumentation and Methods

Abstract
Scanning Mobility CCN Analysis (SMCA) is a technique that allows the investigation of the size-specific CCN activity of a given aerosol (Moore et al, 2010). In the past decade, more than 100 publications have used this technique in the laboratory and in the field. The SMCA experimental analysis has contributed substantially to the scientific understanding of size-resolved cloud droplet formation and aerosol hygroscopicity. However, The SMCA technique was built around the 3080 Electrostatic Classifier, a commercial instrument that, along with its software system, is no longer available. SMPS systems utilizing the 3080 Classifier provided the user with a concentration time series measured by the CPC that extended beyond the end of the scan period. This dataset provided SMCA users access to the time stamp of a temporary rise in particle concentration that occurred while the DMA was returning to low voltage. The timestamp of this ‘retrace bump’ was a vital input into SMCA data analysis, enabling researchers to compare and deduce the size resolved CCN activity with a high degree of accuracy. The current electrostatic classifier technology does not provide the ‘retrace’ data needed for SMCA alignment. Without it, the ability to measure size resolved CCN activation on the order of 2 minutes will be significantly hindered. Current topics of CCN research that may change on temporal scales, such as environmental chamber studies or regional mixing state field studies may lose data resolution and valuable analysis that could have been interpreted by the scanning mobility technique. This work summarizes efforts to meet the needs of the CCN community using the newest particle sizing technology and provides a solution to CCN measurement using the latest available electrostatic classifier information. The proposed solution works around the current limitations of the newer SMPS that do not provide a downscan retrace.