Size-Resolved CCN Spectra of Marine, Continental, and Pyrogenic Aerosols - A Comparison
Abstract
The supersaturation (S) at which an aerosol particle is activated to grow into a cloud droplet depends on the particle size and chemical composition. Currently, there are still many open questions how the complex chemistry of ambient particles influences their cloud nucleating properties. Size resolved measurements of cloud condensation nuclei (CCN) help to separate the effect of particle size from the effect of chemical composition and give new insights into the activation behavior of ambient aerosol particles. Over the past years we measured size resolved CCN spectra during four field and one laboratory experiment, focusing on different aerosol types: Fresh biomass burning aerosol (EFEU), aged continental aerosol (FACE-2004, FACE-2005, MOHp), and marine aerosol (RICO-PRACS). We will compare and contrast the CCN spectra, measured for these aerosol types, and relate the findings to particle chemical composition. A differential mobility analyzer was used to select a fraction of the aerosol particles within a narrow electrical mobility range. These nearly monodisperse particles were passed on to a CCN counter. A condensation particle counter, parallel to the CCN counter, determined the total particle concentration (CN). This information can be used to derive the CCN activation efficiency, defined as the number of CCN divided by the number of CN, at each particle diameter and S. At S=0.4%, marine aerosols are activated at same diameter as pure ammonium sulfate, 50 nm. Continental and pyrogenic aerosol particles require increasingly larger particle diameters for activation, 75 respective 125 nm, indicating the presence of insoluble or poorly soluble material in the particles. In addition the activation curves become less steep, indicating heterogeneities in particle chemical composition and/or shape.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2005
- Bibcode:
- 2005AGUFM.A42B..05F
- Keywords:
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- 0305 Aerosols and particles (0345;
- 4801;
- 4906);
- 0320 Cloud physics and chemistry;
- 0345 Pollution: urban and regional (0305;
- 0478;
- 4251)