Analysis on the Interaction between Turbulence and Secondary Circulation of the Surface Layer at Jinta Oasis in Summer |
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| Authors: | HAN Bo LU Shihua and AO Yinhuan |
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| Institution: | Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000,Cold and Arid Regions Environmental and Engineering Research Institute,Chinese Academy of Sciences, Lanzhou 730000,Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000 |
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| Abstract: | The kinetic energy variations of mean flow and turbulence
at three levels in the surface layer were calculated by using eddy
covariance data from observations at Jinta oasis in 2005 summer. It is found
that when the mean horizontal flow was stronger, the turbulent kinetic
energy was increased at all levels, as well as the downward mean wind at the
middle level. Since the mean vertical flow on the top and bottom were both
negligible at that time, there was a secondary circulation with convergence
in the upper half and divergence in the lower half of the column. After
consideration of energy conversion, it was found that the interaction
between turbulence and the secondary circulation caused the intensification
of each other. The interaction reflected positive feedback between
turbulence and the vertical shear of the mean flow. Turbulent sensible and
latent heat flux anomaly were also analyzed. The results show that in both
daytime and at night, when the surface layer turbulence was intensified as a
result of strengthened mean flow, the sensible heat flux was decreased while
the latent heat flux was increased. Both anomalous fluxes contributed to the
cold island effect and the moisture island effect of the oasis. |
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| Keywords: | heterogeneous atmospheric boundary layer turbulent kinetic energy equations energy conversion secondary circulation oasis effect |
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