The influence of small aerosol particles on the properties of water and ice clouds

In this paper, results are presented of the influence of small organic- and soot-containing particles on the formation of water and ice clouds. There is strong evidence that these particles have grown from nano particle seeds produced by the combustion of oil products. Two series of field experiments are selected to represent the observations made. The first is the CLoud-Aerosol Characterisation Experiment (CLACE) series of experiments performed at a high Alpine site (Jungfraujoch), where cloud was in contact with the ground and the measuring station. Both water and ice clouds were examined at different times of the year. The second series of experiments is the CLOud Processing of regional Air Pollution advecting over land and sea (CLOPAP) series, where ageing pollution aerosol from UK cities was observed, from an airborne platform, to interact with warm stratocumulus cloud in a cloud-capped atmospheric boundary layer. Combining the results it is shown that aged pollution aerosol consists of an internal mixture of organics, sulfate, nitrate and ammonium, the organic component is dominated by highly oxidized secondary material. The relative contributions and absolute loadings of the components vary with location and season. However, these aerosols act as Cloud Condensation Nuclei (CCN) and much of the organic material, along with the other species, is incorporated into cloud droplets. In ice and mixed phase cloud, it is observed that very sharp transitions (extending over just a few metres) are present between highly glaciated regions and regions consisting of supercooled water. This is a unique finding; however, aircraft observations in cumulus suggest that this kind of structure may be found in these cloud types too. It is suggested that this sharp transition is caused by ice nucleation initiated by oxidised organic aerosol coated with sulfate in more polluted regions of cloud, sometimes enhanced by secondary ice particle production in these regions.

Schlagwörter

Fachgebiet (DDC)

Projekt

Veranstaltung

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Enddatum der Ausstellung

Startdatum der Konferenz

Enddatum der Konferenz

Datum der letzten Prüfung

ISBN

ISSN

1359-6640
1364-5498

Sprache

Englisch

Während FHNW Zugehörigkeit erstellt

Nein

Zukunftsfelder FHNW

Publikationsstatus

Veröffentlicht

Begutachtung

Peer-Review der ganzen Publikation

Open Access-Status

Closed

Lizenz

Zitation

CHOULARTON, Thomas W., Keith N. BOWER, Ernest WEINGARTNER, Ian CRAWFORD, Hugh COE, Martin W. GALLAGHER, Michael FLYNN, Jonathan CROSIER, Paul CONNOLLY, Admir Créso TARGINO, M. Rami ALFARRA, Urs BALTENSPERGER, Staffan SJÖGREN, Bart VERHEGGEN, Julie COZIC und Martin GYSEL, 2008. The influence of small aerosol particles on the properties of water and ice clouds. Faraday Discussions. 9 August 2008. Bd. 137, S. 205–222. DOI 10.1039/b702722m. Verfügbar unter: https://irf.fhnw.ch/handle/11654/46700

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