whole_DareRichardAndrew1995_thesis.pdf (17.53 MB)
Mesoscale modelling of the Antarctic katabatic wind over the Lambert Basin
thesisposted on 2023-05-26, 22:13 authored by Dare, Richard Andrew
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."
Rights statementCopyright 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). Thesis (Ph.D.)--University of Tasmania, 1995. Includes bibliographical references (p. 314-324)