Reconciliation of measurements of hygroscopic growth and critical supersaturation of aerosol particles in central Germany 1School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK
10 Dec 2010
2National Centre for Atmospheric Science, University of Manchester, Manchester, UK
Received: 31 May 2010 – Published in Atmos. Chem. Phys. Discuss.: 12 Jul 2010 Abstract. Aerosol physical, chemical and hygroscopic properties were measured in a
range of airmasses during COPS (Convective and Orographically-induced
Precipitation Study) ground-based in June and July of 2007 at the
Hornisgrinde mountain site in the Black Forest, Southwest Germany.
Non-refractory aerosol composition was measured with an Aerosol Mass
Spectrometer, simultaneous to hygroscopic growth factors at 86% relative
humidity and CCN activity measurements for particles of dry (<20%)
diameters 27 to 217 nm, with particle water uptake exhibiting
substantial variability with time and with particle size.
Revised: 28 Nov 2010 – Accepted: 06 Dec 2010 – Published: 10 Dec 2010
Variability in the measurements of hygroscopic growth factor and critical
supersaturation for particles of similar sizes indicates significant
compositional impact on particle water affinity. Critical supersaturation
prediction using a single parameter hygroscopicity approximation derived from
measured HTDMA mean growth factors deviate, beyond measurement uncertainties,
from critical supersaturations derived from CCN measurements. These led to
differences averaging around 35% in the number of CCN (NCCN) for the
most reliable measurements depending on averaging methodology, often very
much larger for individual time periods. This indicates aspects of water
uptake behaviour unresolved in this experiment by the single parameter
representation which, depending on its origin, may have important
consequences on its generalised use.
Citation: Irwin, M., Good, N., Crosier, J., Choularton, T. W., and McFiggans, G.: Reconciliation of measurements of hygroscopic growth and critical supersaturation of aerosol particles in central Germany, Atmos. Chem. Phys., 10, 11737-11752, doi:10.5194/acp-10-11737-2010, 2010.