The Weathermen and Friday Drinks

Every couple of weeks at Mawson, Friday drinks are hosted at a different workplace. It is a way of letting others on station know what different groups do and to understand their role at the station.

Last Friday ‘Team Met’ hosted drinks at the Met office.

Visitors started to arrive at 15:30 just in time to see the preparation of the evening weather balloon flight. The two-day Green Store stocktake of the food, cleaning and toiletries for the 2012 reorder had finished early so before long the office was crowded.

While Rolf kept the operational activities on track Dave explained the finer points of weather balloon observations. The things that interested people most were the 'how far', 'how fast' etc. So most were surprised that the balloons reached 30 km in height, expand till they burst as far as 200 km away and have recorded temperatures 18 km up at around -90 ºC in the depths of winter and recently wind speeds in excess of 300 km/hr.

The function of other instrumentation on station was also described in between cracker biscuits and home brew refills.

Then, to enable people to experience Mawson weather (if they had somehow missed out in the past 8 months), Dave walked them around the various outside meteorological instruments.

Firstly he showed the instrument shelter housing electronic sensors and the calibration checking thermometers and explained the importance of standard conditions for exposing instruments particularly at Mawson which is the longest running temperature observation site in Antarctica. Standard conditions enable changes in climate to be monitored.

Then to the sunshine recorder – an old technology instrument used for measuring sunshine hours. This instrument focusses the sun's rays through a glass sphere that burns a track onto a card with the sun's apparent movement across the sky. (It is the earth that is rotating around its axis and the sun remains stationary) Some joked that it was used as a crystal ball to forecast the weather but others had spotted the meteorological dart board in the office and suggested that it would be more comfortable inside using a dart board for forecasting.

The group then watched a helium balloon fill and release. The balloon filling shed is normally a 'no go' area because of the presence of hydrogen used to fill the balloons. Hydrogen is lighter than air and explosive so requires special systems and care in its use. Hydrogen for weather balloons is made on site using a process that separates hydrogen and oxygen from pure water.

Helium, a non-explosive gas, was used for the balloon release demonstration. When the balloon is filled a radiosonde (scientific instrument) is tied to the balloon. The radiosonde measures temperature, humidity, pressure and wind speed and direction as it is carried by the balloon at 300 metres per minute up into the atmosphere and stratosphere.

After the balloon was released it was back to the warm office to top up those glasses, watch the radiosonde data being received and plotted on the computer and ask questions about the weather. So there was a La Nina last year and the chance of another this year, and gas samples taken for CSIRO by met staff show an increasing trend for carbon dioxide, methane and other greenhouse gases at Mawson in line with global trends. The long term temperature trend at Mawson shows warmer winters with the other seasons being slightly cooler, making the temperatures averaged over the whole year to be cooling slightly in contrast to warming temperature trends measured from Australian stations.

David Morrison