Influence of the boundary layer height on the global air–sea surface fluxes |
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Authors: | Erik Sahlée Ann-Sofi Smedman Ulf Högström |
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Institution: | 1.Rosenstiel School of Marine and Atmospheric Science,University of Miami,Miami,USA;2.Department of Earth Sciences, Meteorology,Uppsala University,Uppsala,Sweden |
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Abstract: | Results from large-eddy simulations and field measurements have previously shown that the velocity field is influenced by
the boundary layer height, z
i
, during close to neutral, slightly unstable, atmospheric stratification. During such conditions the non-dimensional wind
profile, φ
m
, has been found to be a function of both z/L and z
i
/L. At constant z/L, φ
m
decreases with decreasing boundary layer height. Since φ
m
is directly related to the parameterizations of the air–sea surface fluxes, these results will have an influence when calculating
the surface fluxes in weather and climate models. The global impact of this was estimated using re-analysis data from 1979
to 2001 and bulk parameterizations. The results show that the sum of the global latent and sensible mean heat fluxes increase
by 0.77 W m−2 or about 1% and the mean surface stress increase by 1.4 mN m−2 or 1.8% when including the effects of the boundary layer height in the parameterizations. However, some regions show a larger
response. The greatest impact is found over the tropical oceans between 30°S and 30°N. In this region the boundary layer height
influences the non-dimensional wind profile during extended periods of time. In the mid Indian Ocean this results in an increase
of the mean annual heat fluxes by 2.0 W m−2 and an increase of the mean annual surface stress by 2.6 mN m−2. |
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Keywords: | Boundary layer height ERA-40 Latent heat flux Momentum flux Sensible heat flux |
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