High resolution flight observations and numerical simulations: horizontal variability in the wintertime boreal boundary layer |
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Authors: | H Savijärvi T Amnell |
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Institution: | (1) Department of Meteorology, University of Helsinki, Finland, FI |
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Abstract: | Summary High resolution aircraft observations made along flight tracks over inhomogeneous surface in the late wintertime boreal zone
are described and compared to 2D mesoscale model simulations with surface properties defined at 2 km resolution from maps.
All observations displayed the expected small-scale turbulence. On top of that, the near-surface wind speeds (but not directions)
showed mesoscale variations related to local topography and roughness. Upward (but not downward) SW and LW radiative fluxes
and ground temperature also displayed mesoscale variability; in SW radiation this was clearly due to local albedo changes.
In the sensible heat flux there was strong horizontal variation near the surface in correlation with surface types. The above
observed mesoscale along-track variations were reasonably well represented by the mesoscale model simulation. The track-averaged
observed sensible and latent heat flux profiles were in rough agreement with a mixing length approach, which used the track-averaged
wind, temperature and moisture profiles as input (mimicking a first-order turbulence closure scheme of a GCM).
Received September 20, 1999 Revised January 21, 2000 |
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