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Michael Pook
and
Lance Cowled

Abstract

The first Special Observing Period (SOP-1) of the Antarctic First Regional Observing Study of the Troposphere (FROST) was completed in July 1994 and provided a unique opportunity to assemble a comprehensive dataset for the Antarctic region. Data obtained from this intensive collection effort have been undergoing analysis at several centers around the world, including Hobart in Australia. The synoptic analysis program for SOP-1 has been completed in Hobart and, additionally, a reanalysis of a “special week” (22–28 July) has been undertaken, enabling 500-hPa contour fields to be constructed for the region south of 50°S. Results of these analyses for continental Antarctica are presented and comparisons made with operational analyses from numerical models.

Satellite imagery from the Defense Meteorological Satellite Program (DMSP) was employed in the special week reanalysis and has provided evidence of several vortices that moved southward over East Antarctica during the latter part of July 1994 and appeared to decay over the high plateau. Observations from the network of automatic weather stations (AWSs) over East Antarctica were combined with satellite imagery to infer the movement inland of these cyclones.

It is demonstrated that broadscale and synoptic-scale influences contributed to the migration of cyclones over East Antarctica during SOP-1 and, in particular, an association is established between the incidence of atmospheric blocking activity in the Tasman Sea and the inland penetration of lows. The early identification of circulation features in satellite cloud imagery when a favorable broadscale environment has been established and the interpretation of anomaly fields using Antarctic AWSs offer possibilities for the better prediction of the tracks of these small but significant systems.

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John Turner
,
Stephen Pendlebury
,
Lance Cowled
,
Kieran Jacka
,
Marjorie Jones
, and
Philip Targett

The First International Symposium on Operational Weather Forecasting in Antarctica was held in Hobart, Australia, from 31 August to 3 September 1998. There were 40 attendees at the meeting from Australia, Belgium, Brazil, China, France, Italy, Russia, and the United Kingdom. In recent years there has been considerable growth in the requirement for weather forecasts for the Antarctic because of the increases in complex scientific research activities and the rapid growth of tourism to the continent. At many of the research stations there are now sophisticated forecasting operations that make use of the data available from drifting buoys and automatic weather stations, the output from numerical weather prediction systems, and high resolution satellite imagery. The models have considerable success at predicting the synoptic-scale depressions that occur over the ocean and in the coastal region. However, the many mesoscale systems that occur, which are very important for forecasting local conditions, are not well represented in the model fields and their movement is mainly predicted via the satellite data. In the future it is anticipated that high resolution, limited-area models will be run for selected parts of the continent. The symposium showed that great advances had been made during recent years in forecasting for the Antarctic as a result of our better understanding of atmospheric processes at high latitudes, along with the availability of high resolution satellite imagery and the output of numerical models. Outstanding problems include the difficulty of getting all of the observations to the main analysis centers outside the Antarctic in a timely fashion, the lack of upper air data from the Antarctic Peninsula and the interior of the continent, and the poor representation of the Antarctic orography and high latitude processes in numerical models. An outcome of the symposium will be a weather forecasting handbook dealing with the entire continent.

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John Turner
,
Steven Leonard
,
Gareth J. Marshall
,
Michael Pook
,
Lance Cowled
,
Richard Jardine
,
Stephen Pendlebury
, and
Neil Adams

Abstract

The quality of the Antarctic operational analyses that were distributed over the Global Telecommunications System during the First Regional Observing Study of the Troposphere project special observing period of July 1994 is considered. Numerical analyses from the U.K. Meteorological Office, the European Centre for Medium-Range Weather Forecasts, the Australian Bureau of Meteorology, and the U.S. National Centers for Environmental Prediction are compared with high quality analyses prepared using all available late data and high-resolution satellite imagery. The subjective assessment of the analyses indicated that no large, synoptic-scale systems were missing, but major discrepancies were found in terms of the depth of the lows, location errors, and failures to resolve the complexities of systems. Generally, the central pressures of the lows were handled better than the locations of the centers. Only 4 lows out of a total of 161 in the Eastern Hemisphere during the period 22–28 July had to be relocated more than 500 km. High-quality satellite imagery was very important in correcting the locations of the lows and in resolving the structure of multicentered systems, which were often found to be much more complex than analyzed on the operational charts. The satellite imagery was of less value over the continent since some of the lows here, which were analyzed using automatic weather station data, had no cloud associated with them as a result of the atmosphere being very dry. Few changes were made to the positions of anticyclones and only minor modifications to ridges were required. The mean pressure at mean sea level fields for July 1994 as produced by the four models were all very similar, but the Australian model stood out as slightly different over the Amundsen Sea because of large differences in the handling on one large low during the early part of the month. The Phillpot technique for the analysis of the 500-hPa surface over the interior of the continent was of particular value in resolving structure in the circulation.

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Hugh A. Hutchinson
,
T. Stephen Dixon
,
Neil Adams
,
Kieran Jacka
,
Stephen F. Pendlebury
,
Lawrence Marsh
,
Lance H. Cowled
,
Henry R. Phillpot
,
Michael J. Pook
, and
John Turner

Abstract

An overview is presented of the analysis procedures and problems encountered in the FROST reanalysis of weather charts poleward of latitude 50°S carried out in Hobart by the Australian Bureau of Meteorology, with advice from the Institute of Antarctic and Southern Ocean Studies. A summary of findings as a result of the FROST exercise is given and some topics for research projects in the future are identified.

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