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Improvements to meteorological analysis over the Antarctic and Southern Ocean region from the inclusion of additional observing systems

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Jacka, K (2003) Improvements to meteorological analysis over the Antarctic and Southern Ocean region from the inclusion of additional observing systems. Research Master thesis, University of Tasmania.

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Abstract

The in situ meteorological observing network in the Antarctic and Southern Ocean
region is sparsely populated relative to other continents. Numerical weather
prediction skill in Antarctica is poor, and as a scientific community our
understanding of Antarctic atmospheric processes is underdeveloped. Yet the
atmospheric dynamics occurring in the Antarctic region impact greatly on the
weather of populated continents further north. Here several meteorological analysis
and forecasting problems are investigated with close attention to the Antarctic
continent and the surrounding Southern Ocean.
Scatterometer wind data, derived from satellite measurements of microwave
backscatter by the ocean surface, are an important modern source of data for
Southern Ocean Meteorology. Wind speed and direction estimates from the
scatterometer instrument flown on-board the European Space Agency ERS-1
satellite are tested for accuracy against numerical model fields. Alternative
algorithms have been developed by several meteorological agencies to deduce
surface wind speed and direction from microwave backscatter measurements.
Comparison is made between 10m wind estimates generated by two alternative
algorithms and co-located data from the European Centre for Medium Range
Weather Forecasts' numerical analyses. Some limitations in the derivation
algorithms, unique to the Southern Ocean, are detected. A data impact study, conducted within the framework of the Australian Bureau of
Meteorology global data assimilation and prediction system (GASP), was
conducted to assess the influence of ERS-1 scatterometer winds on numerical
analyses and forecasts. The study identified several cases of substantial analysis
impact, predominantly over the Southern Ocean. Mean impact statistics from 120
six-hourly assimilation cycles indicated a small positive impact on 24 and 48 hour
forecast skill. The number of positive impact events exceeded the number of
negative impact events and the inclusion of scatterometer data reduced the
magnitude of forecast errors. The majority of large impact events arose from simultaneous assimilation of two or
more observing systems coincident in time and space. Large discrepancies between
model air-pressure predictions and drifting buoy reports often resulted in the
elimination of the latter on quality control grounds. On numerous occasions the
superposition of scatterometer winds provided sufficient supporting evidence for
the inclusion to proceed and subsequently generate improved analyses and
forecasts.
Another valuable form of remotely sensed atmospheric data comes from the TIROS
Operational Vertical Sounder (TOVS). Estimates of thickness between pressure
surfaces, variously from the surface to 250hPa, were used heavily for
meteorological analysis during the Antarctic First Regional Observing Study of the
Troposphere (1-ROST). Here TOVS estimates are compared with co-incident
radiosonde data from Antarctic and sub-Antarctic meteorological stations,
supporting their validation. The representation of the Antarctic surface temperature inversion in the GASP
analyses is measured against results from observational studies. Improved
boundary layer structure in later versions of the model is confirmed and surface
wind forecasting skill has improved. Fluctuations in inversion depth and strength in
successive model analyses and prognoses is identified as a wind strength
forecasting aid for coastal locations.
The forecast skill of numerical weather prediction systems has increased steadily
over the past two decades. The GASP system, on which the bulk of this work
focuses, has also seen substantial skill increases. Improvements in forecast skill of
the Australian global system have come from a combination of incremental changes
over many years. While horizontal and vertical resolution has increased
substantially, skill improvements in the Antarctic and Southern Ocean region have
also come from the marked increase in data supply and usage. Particularly
important are remotely sensed data, automatic weather stations and drifting buoys.
The potential for further dramatic skill improvement in the years ahead is real.
Proposed future satellite missions will offer a great deal to Antarctic Atmospheric Science. Significant new satellite systems will include NPOESS (USA; programme
beginning 2005), COSMIC (USA/Taiwan; programme beginning 2005), ADEOS-II
(Japan; launch planned for 2002), ENVISAT (European Space Agency; launched
March 2002), Coriolis (USA; launch planned for August 2002) and MetOp-1
(European Space Agency; launch planned for 2005). Together they will provide the
Meteorological Community with advanced atmospheric profiling technology,
improved quality and resolution surface wind data, higher resolution multi-channel
imagery and more. These remote sensing advances will come alongside an
expanding network of automatic weather stations on the Antarctic continent and
ongoing improvements to numerical modelling systems. Antarctic Meteorology is
set to continue to benefit from the incorporation of existing observing systems as
well as from new systems as they become available.

Item Type: Thesis (Research Master)
Keywords: Meteorology
Copyright Information:

Copyright 2003 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 (M.Sc.)--University of Tasmania, 2003. Includes bibliographical references

Date Deposited: 19 Dec 2014 02:45
Last Modified: 23 Sep 2016 01:17
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