Size-resolved aerosol composition and its link to hygroscopicity at a forested site in Colorado

Autor(en)

E. J. T. Levin, A. J. Prenni, B. B. Palm, D. A. Day, P. Campuzano-Jost, P. M. Winkler, S. M. Kreidenweis, P. J. DeMott, J. L. Jimenez, J. N. Smith

Abstrakt

Aerosol hygroscopicity describes the ability of a particle to take up water

and form a cloud droplet. Modeling studies have shown sensitivity of

precipitation-producing cloud systems to the availability of aerosol

particles capable of serving as cloud condensation nuclei (CCN), and

hygroscopicity is a key parameter controlling the number of available CCN.

Continental aerosol is typically assumed to have a representative

hygroscopicity parameter, κ, of 0.3; however, in remote locations

this value can be lower due to relatively large mass fractions of organic

components. To further our understanding of aerosol properties in remote

areas, we measured size-resolved aerosol chemical composition and

hygroscopicity in a forested, mountainous site in Colorado during the

six-week BEACHON-RoMBAS (Bio-hydro-atmosphere interactions of Energy, Aerosols,

Carbon, H_{2O, Organics and Nitrogen–Rocky Mountain Biogenic}

Aerosol Study) campaign. This campaign followed a year-long

measurement period at this site, and results from the intensive campaign

shed light on the previously reported seasonal cycle in aerosol

hygroscopicity. New particle formation events were observed routinely at

this site and nucleation mode composition measurements indicated that the

newly formed particles were predominantly organic. These events likely

contribute to the dominance of organic species at smaller sizes, where

aerosol organic mass fractions were between 70 and 90%. Corresponding

aerosol hygroscopicity was observed to be in the range κ = 0.15–0.22,

with hygroscopicity increasing with particle size. Aerosol chemical

composition measured by an aerosol mass spectrometer and calculated from

hygroscopicity measurements agreed very well during the intensive study, with

an assumed value of κ_org = 0.13 resulting in the best

agreement.

 

Organisation(en)

Aerosolphysik und Umweltphysik

Externe Organisation(en)

University of Eastern Finland, Colorado State University, University of Colorado, Boulder

Journal

Atmospheric Chemistry and Physics

Band

14

Seiten

2657-2667

Anzahl der Seiten

11

ISSN

1680-7316

DOI

https://doi.org/10.5194/acp-14-2657-2014

Publikationsdatum

03-2014

Peer-reviewed

Ja

ÖFOS 2012

103037 Umweltphysik

Schlagwörter

ASJC Scopus Sachgebiete

Atmospheric Science

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/86d6896b-4c45-4aa6-8dcb-97b85621c02d