This week at Mawson: 17 August 2012

Most people at the Australian Antarctic stations are employed by the Australian Antarctic Division but there are a select few who work for the Bureau of Meteorology. Eleven each year in fact. At Mawson the Met Team consists of two people, the Met Tech (electronics technician) Kelvin and the Senior Obs (technical officer observer / Officer in Charge), myself. The other stations have an additional observer and cover more observations.

The met tech works the observations roster, carries out the maintenance and repair of all the met equipment on station and writes the tech reports. The senior obs manages the observations side of the office, rosters, writes the met reports, and is a part of the station leadership team.

During the summer we provide aviation observations for pilots and forecasters as well as ship observations on the Aurora Australis. We also have extra scientific work throughout the year, like the clean air sampling done twice a month that allows the CSIRO to monitor carbon dioxide levels in the atmosphere and routine tasks for the Ionic Prediction Service (IPS).

The major observations covered each day include the synoptic surface observations and the upper air program. The data we collect is sent to Australia and shared around the world through the World Metrological Organisation (WMO). The data is used by meteorologists for real time forecasting, in forecasting models and becomes a part of the Australian Data Archive for Meteorology (ADAM) also known as the climate record.

A synoptic observation records air temperature, humidity, wind speed and direction, and surface pressure from the Automatic Weather Station (AWS) with the observers adding in the manual component of visibility, weather and cloud. Messages are coded and sent every three hours with maximum and minimum temperatures included in the 9am and 3pm observations. This is the information you’ll see on TV, the Bureau’s website or in the newspaper. There are 100 weather groups to choose from, with blowing snow being the most common at Mawson. The duty observer also has the privilege of deciding if it is officially a blizzard (also called a blizz day) or not.

The Mawson upper air program consists of one balloon flight a day. At 1115z (1615 local time) an 800g balloon is sent off with a radiosonde attached underneath. The sonde has sensors to record temperature, pressure, and humidity every two seconds. It uses GPS to calculate its position and movement and thus wind speed and direction. The data collected gives a vertical profile of the atmosphere to about 30km above the station or ideally to 5hpa. It’s primarily used for forecasting, models, climatologically and to calibrate satellites.
The Met Team works a roster, covering seven days a week, 365 days a year, with the only day off being midwinter’s day (it’s a leap year this year!). This means that no matter how bad the weather is outside, Met always gets the full Antarctic experience. Some days there is nowhere better to be working but on blizz days, with the wind howling, snow blowing and visibility down to a few metres. Trying to release the balloon is a challenge.

Once the balloon is inflated, the sonde is attached and then the fun begins. Often there is a pile of snow outside the balloon shed doors, requiring some shovel work before you can release the balloon. Blowing snow may even leak in through the door seals, piling up on the floor. With snow whizzing about, we carefully unhook the balloon and take it outside. The balloon buffets you as you carry it out the doors and on occasion you may even get dragged along before you release it, hoping it won’t be caught in a rotor. Rotors are caused by the wind gusting over and around the balloon shed, and have been known to roll a balloon along the ground, pull it back towards the balloon shed or suddenly push it into the ground destroying the sonde on impact.

In the six and a half months since we’ve been at Mawson we’ve had 15 blizz days, 40 days of blowing snow (visibility <1000m), 188 strong winds days (wind speed 22-33kts) and 123 gales (wind speed >34kts or 63km/h).
We can happily say that we’ve only missed one balloon flight this year due to adverse weather conditions, though we might have had a few second releases and even one third release in an attempt to get the balloon away.

Vicki Heinrich

Sunday 12th August was probably the last day on which we will see the sun actually rise at the station as each day it is rising further to the east and from Sunday the sun will be rising behind the ice plateau and will be out of sight from the station.  We will see the sun as soon as it clears the plateau which will be some time after it has actually risen in the morning.

On Tuesday 14th August after lunch, whilst looking out of the windows in the living quarters, I saw what looked the shape of an angel in the smooth windswept snow on the large blizz tail which runs alongside the building.  This design was made by someone lying on their back in the snow and moving their arms and legs in a circle.  When finished, the so called snow angel had the appearance of a stylised angel.  The movement of the person’s arms forming the wings and the movement of their legs forming the gown.  I found out later that the snow angel I saw was one of many made by Mel during the previous night, but what was she doing lying on the snow at night?

Monday 13th August was unusual weather wise.  We awoke to a typical Mawson blizzard blowing from the SE but by mid-afternoon the wind had dropped to a few knots blowing from the WNW and it was snowing.  When night fell the sky was illuminated by a magnificent aurora which continued for hours explaining why Mel was lying on her back in the snow, gazing at the glorious green curtains in the sky.

Pete ventured outside after midnight because of the aurora which he could see from his bedroom window.  He thought he was seeing things when all the outside lights in the station started shooting light vertically up into the sky like solar pillars.  The air was full of tiny ice crystals (diamond dust) refracting the light causing beams of light going hundreds of metres into the air.  Pete said it was quite something but only lasted 5 or so minutes.

'Diamond dust’ generally forms under clear or nearly clear skies and is referred to as clear sky precipitation.  It is most commonly observed in Antarctica and the Arctic but it can occur anywhere with a temperature well below freezing.  Diamond Dust is usually noticed by brief flashes caused by the crystals tumbling through the air, refracting light.  Vicki, our Met Senior Observer, has recorded diamond dust a few times in the still evening air and solar pillars and sun dogs, the results of diamond dust, have been observed and photographed by many.  However, seeing a vertical beam of light projected hundreds of metres into the sky from many of the outside lights has only been seen and photographed once at Mawson this year by Pete.

Diamond Dust 

by Nancy Ferguson

Bob