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Validation of very high cloud droplet number concentrations in air masses transported thousands of kilometres over the ocean

Martinsson, Bengt G. LU ; Frank, Göran LU ; Cederfelt, Sven Inge ; Berg, Olle H. ; Mentes, Besim ; Papaspiropoulos, Giorgos LU ; Swietlicki, Erik LU ; Zhou, Jingchuan LU ; Flynn, Michael and Bower, Keith N. , et al. (2000) In Tellus, Series B: Chemical and Physical Meteorology 52(2). p.801-814
Abstract


The microstructure of orographic clouds related to the aerosol present was studied during the second Aerosol Characterisation Experiment (ACE-2). Very high cloud droplet number concentrations (almost 3000 cm
-3
) were observed. These high concentrations occurred when clouds formed on a hill slope at Tenerife in polluted air masses originating in Europe that had transported the order of 1000 km over the Atlantic Ocean. The validity of the measured droplet number concentrations was investigated by comparing with measurements of the aerosol upstream of the cloud and cloud interstitial aerosol. Guided by distributions of the ratios... (More)


The microstructure of orographic clouds related to the aerosol present was studied during the second Aerosol Characterisation Experiment (ACE-2). Very high cloud droplet number concentrations (almost 3000 cm
-3
) were observed. These high concentrations occurred when clouds formed on a hill slope at Tenerife in polluted air masses originating in Europe that had transported the order of 1000 km over the Atlantic Ocean. The validity of the measured droplet number concentrations was investigated by comparing with measurements of the aerosol upstream of the cloud and cloud interstitial aerosol. Guided by distributions of the ratios between the measurements, three criteria of typically 30% in maximum deviation were applied to the measurements to test their validity. Agreement was found for 88% of the cases. The validated data set spans droplet number concentrations of 150-3000 cm
-3
. The updraught velocity during the cloud formation was estimated to 2.2 m s
-1
by model calculations, which is typical of cumuliform clouds. The results of the present study are discussed in relation to cloud droplet number concentrations previously reported in the literature. The importance of promoting the mechanistic understanding of the aerosol/cloud interaction and the use of validation procedures of cloud microphysical parameters is stressed in relation to the assessment of the indirect climatic effect of aerosols.

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published
subject
in
Tellus, Series B: Chemical and Physical Meteorology
volume
52
issue
2
pages
14 pages
publisher
Taylor & Francis
external identifiers
  • scopus:18744429641
ISSN
0280-6509
language
English
LU publication?
yes
id
999ee328-7a19-4b70-9c86-a755f7167aa8
date added to LUP
2019-05-16 08:55:40
date last changed
2019-12-03 02:09:06
@article{999ee328-7a19-4b70-9c86-a755f7167aa8,
  abstract     = {<p><br>
                            The microstructure of orographic clouds related to the aerosol present was studied during the second Aerosol Characterisation Experiment (ACE-2). Very high cloud droplet number concentrations (almost 3000 cm<br>
                            <sup>-3</sup><br>
                            ) were observed. These high concentrations occurred when clouds formed on a hill slope at Tenerife in polluted air masses originating in Europe that had transported the order of 1000 km over the Atlantic Ocean. The validity of the measured droplet number concentrations was investigated by comparing with measurements of the aerosol upstream of the cloud and cloud interstitial aerosol. Guided by distributions of the ratios between the measurements, three criteria of typically 30% in maximum deviation were applied to the measurements to test their validity. Agreement was found for 88% of the cases. The validated data set spans droplet number concentrations of 150-3000 cm<br>
                            <sup>-3</sup><br>
                            . The updraught velocity during the cloud formation was estimated to 2.2 m s<br>
                            <sup>-1</sup><br>
                             by model calculations, which is typical of cumuliform clouds. The results of the present study are discussed in relation to cloud droplet number concentrations previously reported in the literature. The importance of promoting the mechanistic understanding of the aerosol/cloud interaction and the use of validation procedures of cloud microphysical parameters is stressed in relation to the assessment of the indirect climatic effect of aerosols.<br>
                        </p>},
  author       = {Martinsson, Bengt G. and Frank, Göran and Cederfelt, Sven Inge and Berg, Olle H. and Mentes, Besim and Papaspiropoulos, Giorgos and Swietlicki, Erik and Zhou, Jingchuan and Flynn, Michael and Bower, Keith N. and Choularton, Tom W. and Mäkelä, Jyrki and Virkkula, Aki and Van Dingenen, Rita},
  issn         = {0280-6509},
  language     = {eng},
  month        = {01},
  number       = {2},
  pages        = {801--814},
  publisher    = {Taylor & Francis},
  series       = {Tellus, Series B: Chemical and Physical Meteorology},
  title        = {Validation of very high cloud droplet number concentrations in air masses transported thousands of kilometres over the ocean},
  volume       = {52},
  year         = {2000},
}