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Mesoscale modelling of the Antarctic katabatic wind over the Lambert Basin


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Dare, Richard Andrew 1995 , 'Mesoscale modelling of the Antarctic katabatic wind over the Lambert Basin', PhD thesis, University of Tasmania.

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The Lambert Glacier drainage basin is a large area of the Antarctic which has
been devoid of conventional meteorological observations, apart from the coastal
meteorological stations. A mesoscale atmospheric model is adapted for use over
the Antarctic continent, and is used with the coastal meteorological records to
simulate boundary layer climatologies over the region. The results are well validated
by new data from oversnow traverses and automatic stations around the
basin. The CSU-Pielke (Pielke and Martin (1981)) numerical mesoscale model
was tested for its suitability over Antarctica. Problems with the surface energy
balance iteration scheme, sea ice surface temperatures, boundary layer height parameterisation
and the representation of cloud in the radiation scheme over the
Antarctic plateau needed to be overcome. Following sensitivity tests to surface
parameters, mean summer and winter modelling results were verified using interpolated
fields from observations available around the Lambert Basin. Analyses
of the meteorological records at Mawson station showed that warm, moist blizzard
winds were associated with cyclonic forcing, and average katabatic winds
consisted of cold, dry air originating further south and flowing as a shallow surface
density current to the coast. "Katabatic-blizzard" winds were the strongest
mean winds found, forced by a combination of cyclonic and drainage flows. The
mesoscale modelling clarified the observations and showed that downslope winds
are likely to be influenced by SW - W synoptic wind directions during July.
Near-surface jets complicated relationships between surface and synoptic winds
because they are fairly independent of synoptic control, existing as relatively
dense parcels of air draining downslope from the plateau. Observations showed
that during summer, wind speed increases were accompanied by increases in thermal
stability, but during winter, by reductions in stability. During January, upper
winds directly influence surface winds through direct transfer of momentum in
the vertical, but during July, vectorial components contribute to the surface flow
forcing. The modelling explained the differences in boundary layer structure between
summer and winter, associated with the seasonal differences in synoptic
flow and also explained why Mawson station is a site of strong, persistent winds.
Once appropriately adapted for Antarctic use, the numerical model was found
to produce reasonable thermal fields with corresponding wind regimes. It then
served as a powerful tool for improving the general understanding of air flow over
Antarctica, on the regional scale, and also for explaining relationships between
surface winds and synoptic forcing over Mawson station.

Item Type: Thesis - PhD
Authors/Creators:Dare, Richard Andrew
Keywords: Wind,
Copyright Holders: The Author
Copyright Information:

Copyright 1995 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1995. Includes bibliographical references (p. 314-324)

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