Simplified treatment of the atmospheric and oceanic boundary layer

• This thesis deals with the evolution of the atmospheric planetary boundary layer, APBL, in which momentum and heat fluxes through the APBL are determined using the bulk values of wind and temperature within the layer. Two ways were explored and tested in determining the primary variables, i.e. the bulk values of wind and temperature: a) the mean temperature is obtained by linear extrapolation from above down into the APBL as suggested by Deardorff (1972), while the mean wind is represented by the surface geostrophic value, b) the mean wind and temperature are determined by solving the integrated momentum and thermodynamic equations within the APBL. The surface transfer coefficients of momentum and heat that were used in the study are those of Deardorff (1972). They depend on the bulk Richardson number, the APBL height and the roughness length. Thus the determination of the fluxes require knowledge of the APBL height and a great deal of attention has been paid for computing the evolution of this quantity. Three different models were used in unstable conditions and three others in stable conditions. Observed Wangara data of Day 33 were used in the computation. The study also involves the application and testing one of the above mentioned APBL height models to the Baltic Sea. Experiments were performed to investigate the effects of the atmospheric forcing on the mixed layer developments. Observed data near Askö for a period of 50 days were used for verification. The study results have shown that the models are able to simulate realistic developments of the APBL and the oceanic mixed layer depths. Deficiencies and uncertainties during the transition period in the atmosphere, in particular, were discussed. 

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

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