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Meso-scale atmospheric flow modifications in the Baltic Sea area
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
1998 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The wind climate in coastal areas often shows large local variations. For example sea-breeze circulations, internal boundary layers (IBL) and low level jets (LLJ) may contribute to more complex wind conditions than otherwise would be expected over the sea. Case studies of wind fields affected by these factors will be treated in this thesis, based on measurements performed in the Baltic Sea area.

A series of pilot balloon trackings showed that LLJs are common in the Baltic Sea area, at least during spring and early summer. 73% of the profiles showed a wind maximum. About 2/3 of the jetlike profiles were identified to be a result of an inertial oscillation in space which develops due to frictional decoupling of the flow over the relatively cold and smooth sea surface.

A case study showed that sea-breeze circulations may strongly affect the wind field at lower levels over most of the Baltic Sea. Even without a sea breeze or a LLJ, the wind field over the Baltic Sea may be quite heterogeneous. For example measurements during spring showed that the slow growth of a stable IBL over the sea gave a wind speed decrease with distance from the coast offshore.

For two case studies during autumn, the IBL evolution inland showed a significantly wind speed decrease at the coastline. The vertical potential temperature gradient was found to be more important for the growth of the IBL than expected, with regard to the near neutral conditions. A model prediction of the IBL height agreed well with data, but a comparison with several simple methods showed that the majority of these models overestimate the IBL height, especially at larger distances.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 1998. , 40 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 381
Keyword [en]
Earth sciences
Keyword [sv]
National Category
Earth and Related Environmental Sciences
Research subject
URN: urn:nbn:se:uu:diva-903ISBN: 91-554-4265-XOAI: oai:DiVA.org:uu-903DiVA: diva2:172293
Public defence
1998-10-02, Axel Hamberg-salen, Geocentrum, Villavägen 16, Uppsala, Uppsala, 10:15
Available from: 1998-09-11 Created: 1998-09-11Bibliographically approved

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