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- Sjöblom, Anna, et al.
(author)
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Comparison Between Eddy-Correlation and Inertial Dissipation Methods in the Marine Atmospheric Surface Layer
- 2004
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In: Boundary-layer Meteorology. - 0006-8314 .- 1573-1472. ; 110:2, s. 141-164
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Journal article (peer-reviewed)abstract
- 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.
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| 5. |
- Sjöblom, Anna, et al.
(author)
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The turbulent kinetic budget over the sea
- 2000
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In: 14th AMS Symposium on Boundary Layer and Turbulance, 7-11 August 2000, Asoen Colorado. ; , s. 507-510
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Conference paper (other academic/artistic)
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| 6. |
- Sjöblom, Anna, et al.
(author)
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The turbulent kinetic energy budget in the marine atmospheric surface layer
- 2002
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In: Journal of Geophysical Research - Oceans and Atmospheres. - 2169-9275 .- 2169-9291. ; 107:C10, s. 616-618
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Journal article (peer-reviewed)abstract
- [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.
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| 7. |
- Sjöblom, Anna, et al.
(author)
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Vertical Structure in the Marine Atmospheric Boundary Layer and its Implication for the Inertial Dissipation Method
- 2003
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In: Boundary-layer Meteorology. - 0006-8314 .- 1573-1472. ; 109:1, s. 1-25
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Journal article (peer-reviewed)abstract
- 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.
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