or
Whatever it is - it's Wet!

 

 


West Coast of Macquarie Island
Photo:     Geof Copson

One of the key factors influencing the commercial development of Macquarie Island in the nineteenth and early twentieth centuries was the weather! It continues to be the one of the uncontrollable element that often determines what can be done on the island.

The severe storms which regularly pass over and around the island have tended to keep human beings away from this isolated spot in the Southern Ocean and have helped to deter them from completely ruining its natural environment. The flora and fauna have learned to adapt to such severe conditions without any external aids and happily survive as long as human beings keep their distance.

 

But what are the meteorological conditions that prevail on the island?
In Table 1 are the facts and figures which show statistically the average weather conditions for the past fifty two years. However, visitors to the island hold the view that these figures do not give a true picture of the real day to day weather that is experienced by parks rangers,scientists and technicians who work there.

The dense fogs, the soaking mists, the howling winds, the pounding seas, the extreme chill factor, the difficult terrain and the smell all "disappear" when looking at these statistics.

Meteorological observers on the island are busy every day collecting the data which makes up the statistical data shown in the table. Temperature, wind speed,dew point, pressure and rainfall are continually recorded while other information such as visibility and cloud cover are recorded every three or six hours.

In addition to regularlly taking air samples, the 'Met. crew' send up special instruments attached to balloons, called radiosondes, which read and send back to the station information about the conditions in the upper atmosphere.

As Ms. Ashleigh Wilson, the Meteorologist at Macquarie Island in March 2000, explains :

 

?The photograph shows a balloon and two radiosondes; the smaller of the two boxes is the Vaisala Radiosonde which records air pressure, temperature and humidity as it ascends through the atmosphere and these are sent up every 12 hours. The larger box is an ozone radiosonde which measures the amount of ozone in the atmosphere it is passing through, and these are released once a week."

 

 


Balloon being released by Ashleigh Wilson
Photo:    Alan Cheshire

 

"The balloon is inflated with enough hydrogen to make it ascend at 300 meters per minute. Each balloon flight lasts 1? to 2 hours and reaches a height of up to 37.5 kilometres. The bigger box of ozone instruments, which cost $900 each, can be reused if it is recovered, but as there is sea in all directions from Macquarie Island the chance of a recovery are very small."

"A Geographic Positioning System (GPS) unit in each box is used to continually measure the balloon?s position as it goes upwards. From this data the wind speed and direction are continuously calculated as the ballon ascends. The ozone radiosonde is just one of the special programme of experiments being run at Macquarie Island which include filtering the air for various elements."


View from the "office window"
Photo:    Doug Ross

"All the data from the radiosondes is relayed to a special receiving set here in the office where it is recorded. It is then transferred to a computer where I can view graphical charts of the air pressure, temperature, humidity, wind speed and direction as the balloon ascends."

"I convert this atmospheric information into internationally recognized code and send it to Hobart, who in turn, send it to Melbourne and other centres around the world. Similar data is collected at exactly the same time from hundreds of other observation sites around the globe, and all this information is then combined to give a very precise view of world wide weather patterns twice every day. The combined results are then used to compile weather forecasts for everyone, including aircraft and shipping."

 

Macquarie Island meteorological data is being used in a world-wide network to monitor Global Warming. Long term weather observations from such places are extremely valuable as they are unaffected by the building of cities, industrial development and changes in vegetation due to farming or logging. Observations made here can therefore more readily detect the long term trends in climate change.

The ability to assess long term trends in the worlds climate will depend on a very careful analysis of all the characteristics of the records from many locations around the world and take into account the natural variability and complexity of weather patterns which are not yet fully understood.

Glyn Roberts
April 2000

References.

Streten N. A., 1988, ?The Climate of Macquarie Island and its Role in Atmospheric Monitoring?; Royal Society of Tasmania, Vol. 122(1).

Francey R. J., Pearman G. I. & Beardsmore D. J., 1988 ?A Southern View of the Global Atmosphere?; Royal Society of Tasmania, Vol 122(1).