Mesoscale Heat Transport Over Complex Terrain By Slope Winds – A Conceptual Model And Numerical Simulations |
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| Authors: | Heike Noppel Franz Fiedler |
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| Institution: | (1) Institute for Meteorology and Climate Research, Universität Karlsruhe/Forschungszentrum Karlsruhe, Kaiserstr. 12, D-76128 Karlsruhe, Germany |
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| Abstract: | Vertical heat fluxes induced by mesoscale thermally driven circulations maycontribute significantly to the subgrid-scale fluxes in large-scale models (e.g.,general circulation models). However, they are not considered in these modelsyet. To gain insight into the importance and possible parameterisation of themesoscale flux associated with slope winds, an analytical (conceptual) modelis developed to describe the relationship between the mesoscale heat flux andatmospheric and land-surface characteristics. The analytical model allows usto evaluate the mesoscale flux induced by slope winds from only a few profilemeasurements within a domain. To validate the analytical model the resultingheat flux profiles are compared to profiles of highly resolved wind and temperaturefields obtained by simulations with a mesoscale numerical model.With no or moderate synoptic wind the mesoscale heat flux generated by the slopewind circulation may be as large as, or even larger than, the turbulent fluxes at thesame height. At altitudes lower than the crest of the hills the mesoscale flux is alwayspositive (upward). Generally it causes cooling within the boundary layer and heatingabove. Despite the simplifications made to derive the analytical model, it reproducesthe profiles of the mesoscale flux quite well. According to the analytical model, themesoscale heat flux is governed by the temperature deviation at the slope surface, thedepth of the slope-wind layer, the large-scale lapse rate, and the wavelength of thetopographical features. |
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| Keywords: | Analytical model Heat flux Mesoscale circulations Numerical model Slope winds |
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