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Turbulent Structure of the Marine Atmospheric Boundary Layer and Its Implications for the Inertial Dissipation Method
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In order to improve climate- and weather forecasting models, a better knowledge of the physical processes taking place in the lowest part of the atmosphere over the oceans is essential. In these models it is often assumed that the atmospheric boundary layer over sea behaves in the same way as that over land. But, the results show that the processes over sea are significantly different, which has to be accounted for in the models.

By using long term measurements it is shown that the surface waves play a very important role for the turbulent structure in the marine atmospheric boundary layer. For example, they give rise to a height structure that can not be found over land. A consequence of this is that measurements from a buoy (at a few meters above the surface) need to be treated different than measurements on a ship (at 10-30 m above the surface).

The wave influence affects the turbulent kinetic energy budget. Besides the height dependency, the imbalance between local production and local dissipation is a function of stability, wave age and wind speed, and the commonly assumed balance can therefore be questioned. This has direct implications for the so called inertial dissipation method, a method often used to determine turbulent fluxes over sea with the aid of measurements from ships and buoys. A comparison with the more direct eddy-correlation method at 10 m height gives that the inertial dissipation method works best for near neutral conditions and growing sea.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2002. , p. 26
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 704
Keywords [en]
Earth sciences
Keywords [sv]
Geovetenskap
National Category
Earth and Related Environmental Sciences
Research subject
Meteorology
Identifiers
URN: urn:nbn:se:uu:diva-1984ISBN: 91-554-5294-9 (print)OAI: oai:DiVA.org:uu-1984DiVA, id: diva2:161595
Public defence
2002-05-17, Axel Hambergsalen, Geocentrum, Villav. 16, Uppsala, 10:00
Opponent
Available from: 2002-04-26 Created: 2002-04-26Bibliographically approved
List of papers
1. The turbulent kinetic energy budget in the marine atmospheric surface layer
Open this publication in new window or tab >>The turbulent kinetic energy budget in the marine atmospheric surface layer
2002 (English)In: Journal of Geophysical Research - Oceans and Atmospheres, ISSN 0148-022A, Vol. 107, no C10, p. 616-618Article in journal (Refereed) Published
Abstract [en]

[1] The terms in the turbulent kinetic energy (TKE) budget have been analyzed according to stability, wave age, and wind speed, using long-term measurements over the sea. The measurements were performed at the island Östergarnsholm in the middle of the Baltic Sea. The results show that there is an imbalance between normalized production and normalized dissipation, also in neutral conditions, and that this imbalance depends not only on stability, which has been previously suggested, but also on wave age and wind speed. For small wave ages and high wind speeds, production is larger than dissipation at neutral conditions. For saturated waves and moderate wind speeds, the sea surface resembles a land surface, while for swell and low wind speeds, dissipation strongly exceeds production. The normalized pressure transport becomes significant during swell conditions, and is not balanced by the normalized turbulent transport. “Inactive” turbulence, where energy is being brought down to the surface from higher levels, is probably the reason for these high values of the pressure transport. The traditional “inertial dissipation method,” where the sum of the transport terms is assumed small and neglected, therefore needs to be corrected for an imbalance between production and dissipation.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-89812 (URN)10.1029/2001JC001016 (DOI)
Available from: 2002-04-26 Created: 2002-04-26 Last updated: 2017-12-14Bibliographically approved
2. Vertical Structure in the Marine Atmospheric Boundary Layer and its Implication for the Inertial Dissipation Method
Open this publication in new window or tab >>Vertical Structure in the Marine Atmospheric Boundary Layer and its Implication for the Inertial Dissipation Method
2003 (English)In: Boundary-layer Meteorology, ISSN 0006-8314, E-ISSN 1573-1472, Vol. 109, no 1, p. 1-25Article in journal (Refereed) Published
Abstract [en]

The structure of the marine atmospheric boundarylayer and the validity ofMonin–Obukhov similarity theory over the seahave been investigated using longterm measurements. Three levels of turbulencemeasurements (at 10 m, 18 mand 26 m) at Östergarnsholm in themiddle of the Baltic Sea have beenanalysed. The results show that turbulentparameters have a strong dependenceon the actual height due to wave influence.The wind profile and thus thenormalised wind gradient are very sensitiveto wave state. The lower part of theboundary layer can be divided into three heightlayers, a wave influenced layerclose to the surface, a transition layer andan undisturbed ‘ordinary’ surfacelayer; the depth of the layers is determinedby the wave state. This heightstructure can, however, not be found for thenormalised dissipation, which is onlya function of the stability, except duringpronounced swell where the actualheight also has to be accounted for. Theresults have implications for the heightvariation of the turbulent kinetic energy(TKE) budget. Thus, the imbalancebetween production and dissipation willalso vary with height according to thevariation of wave state. This, in turn,will of course have strong implicationsfor the inertial dissipation method, inwhich a parameterisation of the TKEbudget is used.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-89813 (URN)10.1023/A:1025407109324 (DOI)
Available from: 2002-04-26 Created: 2002-04-26 Last updated: 2017-12-14Bibliographically approved
3. Comparison Between Eddy-Correlation and Inertial Dissipation Methods in the Marine Atmospheric Surface Layer
Open this publication in new window or tab >>Comparison Between Eddy-Correlation and Inertial Dissipation Methods in the Marine Atmospheric Surface Layer
2004 (English)In: Boundary-layer Meteorology, ISSN 0006-8314, E-ISSN 1573-1472, Vol. 110, no 2, p. 141-164Article in journal (Refereed) Published
Abstract [en]

A comparison of momentum fluxes determined by the eddy-correlation method(ECM) and the inertial dissipation method (IDM) has been performed using longterm measurements over the sea. The measurements were made on the island ofÖstergarnsholm in the middle of the Baltic Sea. The results show that a`classical' form of the inertial dissipation method, i.e., assuming that the transportterms are negligible, and using an effective value for the Kolmogorov constant of0.55, can be used with a mean relative difference between the two methods of about15% for -1 < z/L < 0.5 (z being height and L the Obukhov length). The IDMmethod works best for high wind speeds and neutral conditions. For low windspeeds (U < 6 m s-1) the relation between the two methods is morecomplex. IDM then gives higher values than ECM on the average (about 20%),especially for swell conditions, indicating the need for an imbalance function inthe turbulent kinetic energy budget. Calculations of the effective Kolmogorovconstant, αa, suggest a dependence upon the wave age, αa increasing with increasing wave age, where the value 0.59 fits the data well for saturated waves.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-89814 (URN)10.1023/A:1026006402060 (DOI)
Available from: 2002-04-26 Created: 2002-04-26 Last updated: 2017-12-14Bibliographically approved

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