Saturday, 23 February 2008

How to Deploy an AWS on the Continent

Dave’s Mini-Antarctic Adventure (16th/17th January 2008)

A quick sidestep:..."where in the world is Halley?"

Some of you I believe may be a little confused as to where I am stationed in Antarctica. No doubt you have heard me talk about the “ice-shelf” and “the coast” and “sea-ice” and such like. Well, Halley is located on the Brunt Ice Shelf. A moving floating platform of ice which is flowing off the Antarctic mainland like a glacier.

The ice-shelf itself is moving westwards at a rate of approx 1m per day (I know so because I take a GPS reading every day), and as it is essentially a cantilever off the Antarctic mainland, it is affected by the tide and can oscillate 10m in height from week to week.

Snow accumulates on the ice-shelf at approx 1.2m per year.

These facts combined, the current Halley V station is on legs and has to be jacked up every year. It is the fifth base on the Brunt Ice shelf but the first to be on legs (as the previous bases have been designed to be buried over time but the weight of the snow and ice has eventually crushed them). Halley station has to be rebuilt several kilometres up the ice-shelf every decade or so because it gets too close to the shelf edge and risks breaking off when the shelf edge carves off.

Why not build on the continent? Mainly because the logistics of supporting a station so far “in-land” is too costly and too great a risk. And also because of science. Halley is stationed on a magnetic line of the earth’s natural magnetic field. This opens up the possibility of lots of geeky science which I do not understand or know about. But, being on the magnetic line means that Halley allows its wintering residents to see some kick-arse aurora.

Halley VI is the new generation Halley station, designed to follow the successful design of building a base to stand above the accumulation of snow. The novelty with Halley VI is that each module is built on skis which allows it to be towed every few years to keep it away from the shelf edge.

The Adventure...

I finished my last entry with the mystical and enticing cliff-hanger about my adventure on the continent. Expecting comments to start appearing on my blog about how much people were looking forward to reading about it and how I was the proverbial teaser, I was instead outstanded to find an argument had developed between my solid fan base and Mr. Schollar about who performed the best butler of Boundary Players. (we all know the truth that it is me)

Actually, just looking at my blog, I see I hadn’t left it on a cliff-hanger at all. Meh! never mind. The intention was there.


As the meteorological engineer, one of the projects I had for the summer was to deploy an Automatic Weather Station (AWS) out in the field. The AWS is designed to log the local weather conditions through a suite of sensors. The measurements it takes are temperature, pressure, humidity, wind-speed, wind direction and snow accumulation. The idea is to have it deployed at a remote site on the Antarctic continent and it will log the weather every few minutes and transmit this over a satellite link to a meteorological information pool and is then added to the World Met Organisation for inclusion into their climate models.

“Quite a nifty little project” I can imagine you are thinking to yourselves. “And one not without its risks and dangers too” you conclude your thoughts with.

For a week or so previous I had been gradually building up the AWS as a test setup to verify that all the components were operating correctly.

I then constructed the whole thing fully next to the existing AWS which is temporarily being used at Halley during the Halley VI construction to augment my meteorological observations. The idea was to compare the data sets from both systems to verify that the new one was recording the weather conditions correctly.
It took a good whole day to erect.

With the test successful, the flight to deploy it was given the go ahead. I was informed on Tuesday 15th that it was to go. So, I spent the afternoon dismantling it and prepping it for a flight out to its new home on the continent at M83.

M83 is so called because it is the location of an LPM (magnetometer) station at the 83rd degree south of the equator.

This was a science flight with a difference. Not only was I to deploy the AWS, but the plane was scheduled to stop at A80 to refuel and I was service another LPM and remove a wind generator from a defunct science station. Next stop was to M83 to deploy the AWS. And then onto M84 to service a broken wind generator with the one liberated from M80. This was to be a long day.

So, to recap, the flight was to be as follows:

Halley to A80
A80 to M83
M83 to M84
M84 to A80
A80 to Halley

Now then.
Halley is in fact approximately 1600km from the geological South Pole.

Which is a bloody long way away.

To put it into perspective...the continent of Antarctica is in fact similar in size as the whole of Europe. And a journey from Halley to the pole is approximately the same distance as London to Istanbul, Turkey.

So, once again the plane was loaded with boxes of equipment and other sciency stuff for our epic pan-Antarctica journey. Personnel were Mark the pilot, Simon the science coordinator, and myself.

1st stop was A80 to refuel and service the LPM. And after 45mins we were airborne again heading to M83 to deploy the AWS.

Being so deep on the continent the M83 site is at a height of 6000ft above sea level, and pressure was at the time 760mbar. The air is was easy to get was blowing 15kts...and it was bloody cold!! -23C to be precise.

The AWS cargo was unloaded from the plane, and the next 3 hours was spent erecting the station. Now, it isn’t particularly fun working in such conditions when you have to handle a lot of metal and screw nuts and bolts in -23C. Just the slightest touch sucks the heat from your hands and every 5 minutes you have to stop to try and warm them up again. The worst bit is having to take off the gloves to do the fiddly bits. But we persisted.

And at the end of it, there was the most magnificent looking AWS I had ever seen. I had built this erection, and I was proud. Once the battery box and solar panels were connected up, I hooked up the laptop to test if it was logging data from the sensors. The poor little laptop struggled in the chill, but after 10mins it booted up the software and confirmed my little baby was healthy and logging away.

The completed AWS
(photos courtesy of Simon Coggins)

After an emotional goodbye to the AWS, and we were off again heading to M84 to service the broken wind generator on the LPM.

We landed, Mark and Simon refuelled the plane, and I walked the 500m to the LPM. I swapped the wind generator, tied it down and turned around...and beheld a most amazing scene. It was a simple scene, but the feeling associated with it filled me with a huge sense of awe. Here I shall try to describe it as my camera battery had failed in the cold at M83 and I had forgot my spares.

I was looking at the plane in the distance 500m away. The wind was causing a moderate drift of snow up to 1ft off the ground. The sun was shining brightly with not a cloud in the sky. All around me was a pure white landscape full of sastrugi. The drifting snow snaked over the undulations of the sastrugi like a fluid. My view of the plane in the distance was obscured slightly by the drift...with it’s landing gear hidden it seemed to just float on the drift. And the sun was reflecting off its tail fin. Suddenly I realised I was standing on my own, a mere 500km from the South Pole looking at this sight. The plane was my only link to society...a lifeline to other people. I was overwhelmed with the feelings of remoteness and insignificance mixed with awe and splendour. Magnificent stuff.

I headed back and joined the others. We were soon airborne and heading back to Halley.
You can follow the link below to see a Google Maps view of the sites I visited. If you have it, follow the link to open up Google Earth. It gives a better perspecive of the sites in relation to the continent

Google Maps view of AWS trip

By the time we were flying near A80 again, weather reports from Halley were not ideal. (Ags was covering met in my absence, having been a metbabe herself at Rothera). Mark decided not to risk going back to base and landing in low visibility conditions, and so we turned back to M80 to camp the evening there instead.

Camping out in the middle of Antarctica with the Shackleton Mountains as a backdrop! Cool.

By the time we landed it was 0100hrs and we were hungry. After a bite to eat out of the man-food box, we bedded down in the plane cargo hold. Luckily the sleeping systems we have in the Antarctic are cosy, cosy, cosy. Even in -20C inside the metaphorical metal box of the Twin Otter aircraft.

In the morning we refuelled and headed back to Halley. But not without first buzzing the trailer park 20km away which is the Halley VI prep site.

Thus completing my mini-Antarctic adventure.

And since then I have been checking the data being produce by my little AWSbaby at M83 each day. The data it transmits now goes into the World Meteorological Organisation databanks and helps feed the global weather models. Forgive me if I have a little pride in helping towards that.


Anonymous said...

Great stuff as always David.


Anonymous said...

Wow David.

Mum x

Anonymous said...

What is / are sastrugi? Sounds like italian cuisine to me!


Dave Stephenson said...

Sastrugi are undulations and ridges in the snow surface caused by the erosion of the snow from wind and ice/snow particles. They are very much similar to sand dunes, only that they are on a much smaller scale and actually lie parallel to the wind which created them.

Anonymous said...

There is more than one AWS in existence?

I thought one was more than enough but, I was wrong..........?

Mum xx