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An improved Ekman layer Approximation For Smooth Eddy Diffusity Profiles
Stockholm University, Faculty of Science, Department of Meteorology .
Aeronautical Meteorological Division, Croatia Control Ltd., Zagreb .
Stockholm University, Faculty of Science, Department of Meteorology .
2005 (English)In: Boundary-Layer Meteorology, ISSN 0006-8314, Vol. 115, no 3, 399-407 p.Article in journal (Refereed) Published
Abstract [en]

The Ekman boundary-layer model is extended analytically for a gradually varying eddy diffusivity K(z) ≥ 0, z ≥ 0. A solution for the Ekman layer is provided having similar structure to the constant-K case; that is, exponentially decaying sine functions for the two horizontal wind components. The analytical asymptotic solution compares well with its numerical counterpart for various K(z). The result can be useful in theoretical studies such as Ekman pumping, for efficient estimation of the Ekman layer profiles in various analyses with near-neutral stratifications, or for a rapid initialization of mesoscale models

Place, publisher, year, edition, pages
Springer , 2005. Vol. 115, no 3, 399-407 p.
Keyword [en]
Boundary-layer pumping, Lambert’s W, WKB
National Category
Meteorology and Atmospheric Sciences
Research subject
Meteorology
Identifiers
URN: urn:nbn:se:su:diva-23223DOI: 10.1007/s10546-004-5940-0OAI: oai:DiVA.org:su-23223DiVA: diva2:190802
Note
Part of urn:nbn:se:su:diva-197Available from: 2004-05-25 Created: 2004-05-25 Last updated: 2010-01-22Bibliographically approved
In thesis
1. Near surface atmospheric flow over high latitude glaciers
Open this publication in new window or tab >>Near surface atmospheric flow over high latitude glaciers
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis various descriptions of the near surface atmospheric flow over a high latitude glacier is used in an effort to increase our understanding of the basic flow dynamics there.

Through their contribution to sea-level change, mountain glaciers play a significant role in Earth’s climate system. Properties of the near surface atmospheric flow are important for understanding glacier response to climate change.

Here, the near surface atmospheric flow is studied from several perspectives including the effects of both rotation and slope. Rotation is an important aspect of most atmospheric flows and its significance for mesoscale flows have gained recognition over the last years. Similarly, the very stable boundary layer (VSBL) has lately gained interest. Within a VSBL over sloping terrain katabatic flow is known to be usual and persistent. For the present thesis a combination of numerical and simple analytical models as well as observations from the Vatnajökull glacier on Iceland have been used. The models have continuously been compared to available observations. Three different approaches have been used: linear wave modeling, analytic modeling of katabatic flow and of the Ekman layer, and numerical simulations of the katabatic flow using a state of the art mesoscale model. The analytic models for the katabatic flow and the Ekman layer used in this thesis both utilizes the WKB method to allow the eddy diffusivity to vary with height. This considerably improves the results of the models. Among other findings it is concluded that: a large part of the flow can be explained by linear theory, that good results can be obtained for surface energy flux using simple models, and that the very simple analytic models for the katabatic flow and the Ekman layer can perform adequately if the restraint of constant eddy diffusivity is relieved.

Place, publisher, year, edition, pages
Stockholm: Meteorologiska institutionen (MISU), 2004. 22 p.
Keyword
Stable boundary layer, Ekman layer, Katabatic flow, gravity wave, low-level jets
National Category
Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:su:diva-197 (URN)91-7265-913-0 (ISBN)
Public defence
2004-06-15, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 8 C, Stockholm, 10:00
Opponent
Supervisors
Available from: 2004-05-25 Created: 2004-05-25 Last updated: 2011-02-17Bibliographically approved

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