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A total turbulent energy closure model for neutrally and stably stratified atmospheric boundary layers
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
University of Helsinki. Division of Atmospheric Sciences, Department of Physical Sciences.
Nansen Environmental and Remote Sensing Center, Bergen.
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2007 (English)In: Journal of the Atmospheric Sciences, ISSN 0022-4928, Vol. 64, no 11, 4113-4136 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a turbulence closure for neutral and stratified atmospheric conditions. The closure is based on the concept of the total turbulent energy. The total turbulent energy is the sum of the turbulent kinetic energy and turbulent potential energy, which is proportional to the potential temperature variance. The closure uses recent observational findings to take into account the mean flow stability. These observations indicate that turbulent transfer of heat and momentum behaves differently under very stable stratification. Whereas the turbulent heat flux tends toward zero beyond a certain stability limit, the turbulent stress stays finite. The suggested scheme avoids the problem of self-correlation. The latter is an improvement over the widely used Monin–Obukhov-based closures. Numerous large-eddy simulations, including a wide range of neutral and stably stratified cases, are used to estimate likely values of two free constants. In a benchmark case the new turbulence closure performs indistinguishably from independent large-eddy simulations.

Place, publisher, year, edition, pages
2007. Vol. 64, no 11, 4113-4136 p.
National Category
Meteorology and Atmospheric Sciences
Research subject
Meteorology
Identifiers
URN: urn:nbn:se:su:diva-24080DOI: 10.1175/2007JAS2294.1ISI: 000251283000024OAI: oai:DiVA.org:su-24080DiVA: diva2:196697
Note
Part of urn:nbn:se:su:diva-6585Available from: 2007-02-01 Created: 2007-02-01 Last updated: 2010-01-22Bibliographically approved
In thesis
1. On the Arctic Boundary Layer: From Turbulence to Climate
Open this publication in new window or tab >>On the Arctic Boundary Layer: From Turbulence to Climate
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The boundary layer is the part of the atmosphere that is in direct contact with the ground via turbulent motion. At mid-latitudes the boundary layer is usually one or a few kilometers deep, while in the Arctic it is much more shallow, typically a few hundred meters or less. The reason is that here the absolute temperature increases in the lowest kilometer, making the boundary layer semi-permanently stably stratified. The exchange of heat, momentum and tracers between the atmosphere, ocean and ground under stable stratification is discussed from an observational, modeling and climate-change point of view. A compilation of six observational datasets, ordered by the Richardson number (rather than the widely used Monin-Obukhov length) reveals new information about turbulence in the very stably stratified regime. An essentially new turbulence closure model, based on the total turbulent energy concept and these observational datasets, is developed and tested against large-eddy simulations with promising results. The role of mesoscale motion in the exchange between the atmosphere and surface is investigated both for observations and in idealized model simulations. Finally, it is found that the stably stratified boundary layer is more sensitive to external surface forcing than its neutral and convective counterparts. It is speculated that this could be part of the explanation for the observed Arctic amplification of climate change.

Place, publisher, year, edition, pages
Stockholm: Meteorologiska institutionen (MISU), 2007. 165 p.
Keyword
Atmospheric boundary layers, Turbulence, Stable stratification, Gravity waves, Mesoscale motion, Arctic climate
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences
Identifiers
urn:nbn:se:su:diva-6585 (URN)91-7155-373-8 (ISBN)
Public defence
2007-02-23, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 10:00
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Supervisors
Available from: 2007-02-01 Created: 2007-02-01Bibliographically approved

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