Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
A transitioning Arctic surface energy budget: the impacts of solar zenith angle, surface albedo and cloud radiative forcing
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
Show others and affiliations
2011 (English)In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 37, no 7-8, 1643-1660 p.Article in journal (Refereed) Published
Abstract [en]

Snow surface and sea-ice energy budgets were measured near 87.5A degrees N during the Arctic Summer Cloud Ocean Study (ASCOS), from August to early September 2008. Surface temperature indicated four distinct temperature regimes, characterized by varying cloud, thermodynamic and solar properties. An initial warm, melt-season regime was interrupted by a 3-day cold regime where temperatures dropped from near zero to -7A degrees C. Subsequently mean energy budget residuals remained small and near zero for 1 week until once again temperatures dropped rapidly and the energy budget residuals became negative. Energy budget transitions were dominated by the net radiative fluxes, largely controlled by the cloudiness. Variable heat, moisture and cloud distributions were associated with changing air-masses. Surface cloud radiative forcing, the net radiative effect of clouds on the surface relative to clear skies, is estimated. Shortwave cloud forcing ranged between -50 W m(-2) and zero and varied significantly with surface albedo, solar zenith angle and cloud liquid water. Longwave cloud forcing was larger and generally ranged between 65 and 85 W m(-2), except when the cloud fraction was tenuous or contained little liquid water; thus the net effect of the clouds was to warm the surface. Both cold periods occurred under tenuous, or altogether absent, low-level clouds containing little liquid water, effectively reducing the cloud greenhouse effect. Freeze-up progression was enhanced by a combination of increasing solar zenith angles and surface albedo, while inhibited by a large, positive surface cloud forcing until a new air-mass with considerably less cloudiness advected over the experiment area.

Place, publisher, year, edition, pages
2011. Vol. 37, no 7-8, 1643-1660 p.
National Category
Meteorology and Atmospheric Sciences
Identifiers
URN: urn:nbn:se:su:diva-44323DOI: 10.1007/s00382-010-0937-5ISI: 000295522600022OAI: oai:DiVA.org:su-44323DiVA: diva2:360986
Note
authorCount :10Available from: 2010-11-05 Created: 2010-11-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Arctic clouds - interactions with radiation and thermodynamic structure
Open this publication in new window or tab >>Arctic clouds - interactions with radiation and thermodynamic structure
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Clouds play in important role in the climate system through their interaction with radiation. Globally, clouds tend to cool the Earth by reflecting solar radiation and shading the surface. Over the Arctic, clouds tend to have the opposite impact, where they instead warm the surface through the cloud greenhouse effect because the surface is generally quite reflective. The magnitude and overall effect of clouds on the surface varies significantly with the surface, cloud and thermodynamic characteristics and can have large impacts on the energy budget at the surface.

Low-level central-Arctic stratus clouds interact with the thermodynamics in a manner differently than sub-tropical stratus. Observations from several Arctic observatories indicate that these clouds penetrate and persist within stable temperature inversion structures, rather than being limited to the base of the stable layer as observed in the subtropics. It is hypothesized that such interactions with the thermodynamics can impact for example the cloud phase, lifetime, and their relationship with the sub-cloud layer and surface. Analysis indicates both the thermodynamic setting and the cloud properties affect the vertical location of the cloud top relative to inversion base. Hypothetical longwave radiative impacts resulting from liquid water redistributions are identified and discussed.

Clouds primarily influence the energy at the surface via interactions with radiation. Measurements from the central Arctic suggest that the transition of season from melting to freezing was largely determined by the presence, or absence, of liquid-containing clouds and the incumbent cloud longwave warming effect. The components affecting the cloud-radiative forcing are described with relation to the energy budget and the change of season. Additionally, the influence of altering cloud condensation nuclei as a mechanism for limiting cloud liquid water is shown to have strong influences on surface temperature and lower atmospheric stability.

Finally, regional climate models, RCMs, are evaluated against an annual dataset to assess the ability of RCMs to represent cloud and radiation processes in the Arctic. It is shown that both inter-model and model-observation spread are rather significant. Biases in the cloud representations yield distinct biases in the radiative fluxes, and can result in significant local climate variations solely through these parameters.

Place, publisher, year, edition, pages
Stockholm: Department of Meteorology, Stockholm University, 2010. 46 p.
Keyword
Arctic, stratus, radiation, thermodynamic structure, cloud radiative forcing, seasonal transition
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences
Identifiers
urn:nbn:se:su:diva-43935 (URN)978-91-7447-176-2 (ISBN)
Public defence
2010-12-03, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Accepted. Paper 4: Manuscript published in Atmospheric Chemistry and Physics Discussions.Available from: 2010-11-11 Created: 2010-11-01 Last updated: 2010-11-11Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Sedlar, JosephTjernström, MichaelLeck, Caroline
By organisation
Department of Meteorology
In the same journal
Climate Dynamics
Meteorology and Atmospheric Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 69 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf