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  • Cold air outbreak  (1)
  • Research aircraft  (1)
  • Springer  (2)
  • Elsevier
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  • Springer  (2)
  • Elsevier
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Boundary layer meteorology 84 (1997), S. 45-65 
    ISSN: 1573-1472
    Keywords: Boundary-Layer development ; Vortex rolls ; Cold air outbreak
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The development of the boundary layer during a cold air outbreak in the FramStrait is documented by aircraft measurements. The convection was organisedinto roll vortices with aspect ratios increasing from 2.9 near the ice edgeto more than 6 at 100 km further downstream. This increase coincides with anincrease of the latent heat release in the cloud layer. The stability parameter-zi/L varies from about zero at the ice edge to 30 at a distance of 200 kmdownstream over open water where the satellite picture still shows cloudstreets. The increase is mainly due to the deepening of the boundary layer.The turbulent vertical sensible and latent heat fluxes near the surface amountto 400 W m-2 within a 300 km off-ice zone. 25% of the upward heat fluxin the subcloud layer is carried out by organised roll motions. Experimentswith a 2-dimensional non-hydrostatic model show a similar roll aspect ratio inthe first 50 km, but further downstream where condensational heating is moreimportant the modelled roll wavelengths are distinctly smaller than the observedones.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Boundary layer meteorology 95 (2000), S. 211-230 
    ISSN: 1573-1472
    Keywords: Research aircraft ; Flight pattern ; Mesoscale model ; Heat flux ; Sea-ice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A method is presented for selecting the optimal flight patterns for airbornemeteorological measurements in various flow situations. The method is basedon systematic utilisation of mesoscale model fields. Flow overan Arctic sea-ice boundary zone is modelled, and it is assumed that the mesoscale model fields represent the true state of the atmosphere, and that each possible flight pattern yields a different sample of the true fields. A plan for the basic structure of the flight pattern is assumed, and then the unexplained variance, i.e., the difference between the true variance and the sample variance, of a quantity of interest is calculated for a variety of possible flight patterns. Different target quantities are considered, such as wind speed, air temperature, and the turbulent fluxesof momentum and sensible heat. The optimal flight pattern is defined byminimisation of the unexplained variance, and often depends on the quantitywe are interested in. For sawtooth patterns, the optimal flight pattern was sensitive to the maximum ascent angle of the aircraft. In flight patterns designed for turbulence measurements, the optimal pattern was different for the unexplained variance of the turbulent fluxes and for the unexplained total heat content of the convective layer.
    Type of Medium: Electronic Resource
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