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A study of the indirect aerosol effect on subarctic marine liquid low-level clouds using MODIS cloud data and ground-based aerosol measurements

Sporre, Moa LU ; Glantz, Paul; Tunved, Peter; Swietlicki, Erik LU ; Kulmala, Markku and Lihavainen, Heikki (2012) In Atmospheric Research 116. p.56-66
Abstract
Cloud microphysics is substantially affected by aerosol loading and the resulting changes in the reflective properties of the clouds can significantly affect the global radiation budget. A study of how marine low-level clouds over Barents Sea and the northern parts of the Norwegian Sea are affected by air mass origin has been performed by combining ground-based aerosol measurements with satellite cloud retrievals. Aerosol number size distributions have been obtained from measurement stations in northern Finland, and a trajectory model has been used to estimate the movement of the air masses. To identify anthropogenic influences on the clouds, the dataset has been divided according to aerosol loading. The clean air masses arrived to the... (More)
Cloud microphysics is substantially affected by aerosol loading and the resulting changes in the reflective properties of the clouds can significantly affect the global radiation budget. A study of how marine low-level clouds over Barents Sea and the northern parts of the Norwegian Sea are affected by air mass origin has been performed by combining ground-based aerosol measurements with satellite cloud retrievals. Aerosol number size distributions have been obtained from measurement stations in northern Finland, and a trajectory model has been used to estimate the movement of the air masses. To identify anthropogenic influences on the clouds, the dataset has been divided according to aerosol loading. The clean air masses arrived to the investigation area from the north and the polluted air masses arrived from the south. Satellite derived microphysical and optical cloud parameters from the Moderate Resolution Imaging Spectrometer (MODIS) have then been analyzed for days when the trajectories coincided with marine low-level clouds over the investigated area. The cloud optical thickness (tau), cloud depth (H) and droplet number concentration (N-d) were significantly higher for the polluted days compared to the clean conditions, while the opposite was found for the cloud droplet effective radius (r(e)). The H and N-d were derived from the satellite retrievals of tau and r(e). Furthermore, calculations of the aerosol cloud interaction relationship (ACI), relating N-d to boundary layer aerosol concentrations, resulted in a value of 0.17, which is in line with previous remote sensing studies. The results demonstrate that ground-based aerosol measurements can be combined with satellite cloud observations to study the indirect aerosol effect, and that the microphysics of marine sub-polar clouds can be considerably affected by continental aerosols. (C) 2011 Elsevier B.V. All rights reserved. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Aerosol-cloud interactions, Cloud satellite retrievals, MODIS, Ground-based aerosol measurements
in
Atmospheric Research
volume
116
pages
56 - 66
publisher
Elsevier
external identifiers
  • wos:000308682500006
  • scopus:84865152069
ISSN
1873-2895
DOI
10.1016/j.atmosres.2011.09.014
project
MERGE
language
English
LU publication?
yes
id
6a833afc-1f00-4cdc-9566-accce338a120 (old id 3189667)
date added to LUP
2012-12-04 14:48:43
date last changed
2017-01-08 03:06:25
@article{6a833afc-1f00-4cdc-9566-accce338a120,
  abstract     = {Cloud microphysics is substantially affected by aerosol loading and the resulting changes in the reflective properties of the clouds can significantly affect the global radiation budget. A study of how marine low-level clouds over Barents Sea and the northern parts of the Norwegian Sea are affected by air mass origin has been performed by combining ground-based aerosol measurements with satellite cloud retrievals. Aerosol number size distributions have been obtained from measurement stations in northern Finland, and a trajectory model has been used to estimate the movement of the air masses. To identify anthropogenic influences on the clouds, the dataset has been divided according to aerosol loading. The clean air masses arrived to the investigation area from the north and the polluted air masses arrived from the south. Satellite derived microphysical and optical cloud parameters from the Moderate Resolution Imaging Spectrometer (MODIS) have then been analyzed for days when the trajectories coincided with marine low-level clouds over the investigated area. The cloud optical thickness (tau), cloud depth (H) and droplet number concentration (N-d) were significantly higher for the polluted days compared to the clean conditions, while the opposite was found for the cloud droplet effective radius (r(e)). The H and N-d were derived from the satellite retrievals of tau and r(e). Furthermore, calculations of the aerosol cloud interaction relationship (ACI), relating N-d to boundary layer aerosol concentrations, resulted in a value of 0.17, which is in line with previous remote sensing studies. The results demonstrate that ground-based aerosol measurements can be combined with satellite cloud observations to study the indirect aerosol effect, and that the microphysics of marine sub-polar clouds can be considerably affected by continental aerosols. (C) 2011 Elsevier B.V. All rights reserved.},
  author       = {Sporre, Moa and Glantz, Paul and Tunved, Peter and Swietlicki, Erik and Kulmala, Markku and Lihavainen, Heikki},
  issn         = {1873-2895},
  keyword      = {Aerosol-cloud interactions,Cloud satellite retrievals,MODIS,Ground-based aerosol measurements},
  language     = {eng},
  pages        = {56--66},
  publisher    = {Elsevier},
  series       = {Atmospheric Research},
  title        = {A study of the indirect aerosol effect on subarctic marine liquid low-level clouds using MODIS cloud data and ground-based aerosol measurements},
  url          = {http://dx.doi.org/10.1016/j.atmosres.2011.09.014},
  volume       = {116},
  year         = {2012},
}