The Atmospheric Boundary Layer during Swell: A Field Study and Interpretation of the Turbulent Kinetic Energy Budget for High Wave Ages

Abstract Analysis of the turbulent kinetic energy (TKE) budget for five slightly unstable cases with swell has been performed based on measurements of mechanical production, buoyancy production, turbulent transport, and dissipation at five levels over the sea, from 2.5 to 26 m. The time rate of chan...

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Bibliographic Details
Published inJournal of the atmospheric sciences Vol. 66; no. 9; pp. 2764 - 2779
Main Authors HÖGSTRÖM, U, SMEDMAN, A, SAHLEE, E, DRENNAN, W. M, KAHMA, K. K, PETTERSSON, H, ZHANG, F
Format Journal Article
LanguageEnglish
Published Boston, MA American Meteorological Society 01.09.2009
Subjects
Atmosphere
Atmospheric boundary layer
Boundary layers
Earth sciences
Earth, ocean, space
Exact sciences and technology
External geophysics
Field study
Geovetenskap
Height
Kinetic energy
Meteorology
NATURAL SCIENCES
NATURVETENSKAP
Physics of the high neutral atmosphere
Surface waves
Wind speed
Wind field
winds
Atmospheric boundary layer
Wind velocity
Turbulence energy
Height
swells
Travelling wave
Swell effect
buoyancy
Turbulent transport
stability
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Summary:Abstract Analysis of the turbulent kinetic energy (TKE) budget for five slightly unstable cases with swell has been performed based on measurements of mechanical production, buoyancy production, turbulent transport, and dissipation at five levels over the sea, from 2.5 to 26 m. The time rate of change and advection of TKE were found to be small, so the TKE residual is interpreted as an estimate of the pressure transport term (Tp). In two cases with high wave age, the Tp term is a gain at all heights. For three cases with smaller wave age, Tp is a loss in the TKE budget below 5–10 m and a gain for greater heights, where the decrease is exponential, thus showing the combined effects of swell waves and a range of waves traveling slower than the wind. The TKE budget for a case with growing sea but similar wind speed and stability as some of the swell cases has Tp close to zero at all heights. It is shown that the observed characteristic wind profile with either a low-level maximum in the 5–10-m range or a distinct “knee” at that height is an effect of the Tp term.
Bibliography:ObjectType-Article-2
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ISSN:0022-4928
1520-0469
1520-0469
DOI:10.1175/2009JAS2973.1