This week at the station
This week at Davis: 12 July 2013
Ozone sonde flights resume
We have just started doing weekly ozone sonde flights again for the all important spring season, after forgetting all about them since last December. Like our regular daily sonde flights, the purpose is to bring back data about the state of the atmosphere, with the sonde carried by a big hydrogen filled balloon, transmitting back information over radio waves to our Bureau of Meteorology computer.
A normal sonde is the size of your fist and measures temperature, humidity, and atmospheric pressure, along with a GPS which measures wind direction and speed as the balloon rises with the air at about five metres per second. We release these every day and the data is mostly for weather forecasting models and climate records. The balloons rise to a height of 20-30 kilometres before they burst. In fact some months ago I even found the remains of one on a walk about ten kilometres from station! But most will be carried much further away. The chances of one landing on your head are quite low.
The ozone sonde is another package in addition to the normal sonde which has a little pump that sucks in air. This then goes to two little chemical cells, an anode and a cathode, where strange chemistry stuff happens. Don’t ask me about chemistry, it’s only a step above alchemy as far as I’m concerned – but the result is that a tiny electrical current indicates how much ozone gas is present.
Ozone is a company based in southern France that makes great paraglider wings and kites. It is also a gas that naturally occurs as UV radiation is absorbed in the stratosphere (higher than ten kilometres). The “ozone hole” you have probably heard about was discovered in 1985 and is due to the damaging affects of aerosols for various industrial and commercial applications containing CFC’s which were then banned, with production completely phased out by 1996.
Now in 2013 it looks like after the damage done decades ago, the ozone layer may finally be starting to recover. If it turns out to be true it will be great news. Although it looks like no matter what, I’ll still have to use sunscreen for the next several decades. Nevertheless, we were told during training that ozone flights this year could be the ones to confirm whether the ozone hole recovery is a trend or an anomaly.
Now would be a good time to thank the Davis support staff. They have recently done a great job fixing the ventilation fan. This is one of the safety systems we have for working with the hydrogen gas in the balloon room. It was starting to sound more like a jet turbine than a ventilation fan, and as we didn’t have any spare parts on station, we relied on some diesel mechanic magic to fix it before it self destructed. They managed to replace fan shaft and bearings without any interruption to our balloon programme. Good job!
To set up an ozone sonde takes quite some time. It is commenced over a week before the flight, and includes various tests, measurements, and checks. The sondes are also quite expensive, so you can imagine that it is quite disappointing if you see your package hit the ground and damage the delicate sonde package when you release the balloon. Ideally the winds will be light but for my release a blow had peaked just the night before and I was a little nervous.
The weather (wind) forecast for the next few days wasn’t looking any better so I decided to give it a go, and with a little adrenaline I ran the balloon out the door and got it away safely in 25 knots. For the next few hours I kept an eye on it on the computer as it rose to a height of 27754 metres before the balloon burst. With an atmospheric pressure reaching 9.9hPa the balloon would have expanded to approximately one hundred times the original volume! That was definitely a good result, and what’s more, the instrumentation inside continued to function and deliver good data, even with outside temperatures getting as low as -89.3 degrees Celsius. Since I had to get up an hour earlier to prepare it, I was very happy it worked!
On the topic of ozone, as I write this I think I have spotted another polar stratospheric cloud (PSC). PSC’s look pretty, but they actually are associated with ozone depletion. Since they are so high, they are illuminated by the sun in twilight hours, when normal clouds (stratocumulus, altostratus, cirrus, etc) are still below the suns rays. At this time of year we have a lot of twilight hours so we see them more often. I’ve also spotted them on 3, 4, 18 June.
How deep is Deep Lake?
This weekend I went out with Doc and Rich to do the monthly depth readings of Deep Lake. Yes, we know it’s deep! But how deep?
Rich and I also did the readings last month, and the first thing we noticed is that now there is a lot less snow on the surrounding rocky slopes. With the sun not rising all month, it certainly hasn’t melted! But we suspect that the strong blizzard on June 10, which had gusts peaking at 82 knots, has blown it all away.
It makes walking easier in parts where the snow has blown away and you can walk on rocks. But in other areas the wind has packed a 5cm thick crust, which tends to break just as you put weight on it, sending you crashing through to the soft snow underneath. All part of the fun.
It was really relaxing sitting next to the lake, listening to the ripples of the water on the shore. Something we haven’t heard in a while with everything around here being frozen solid. I said we should have had our midwinter swim here, to save us digging a hole in the ice! But of course it isn’t any warmer here – being hypersaline it is actually a lot colder. No, I couldn’t convince Doc to go for a swim.
So, the question on everyone’s lips? “How deep is Deep Lake?” Well, the surface of the lake is 51 metres below sea level. I don’t know exactly how deep the bottom is but all I can say is that it is one centimetre deeper this month than it was last month! I blame the blizzard again, for blowing snow into it.
After Deep Lake we walked back to the quads and continued our busy little journey. First we stopped at Brookes hut to change out a medical kit, and then off to Bandits hut to collect my tripod which I’d strategically left there a few weeks ago. And finally we returned via the very scenic iceberg alley in the fading light, to finish off a great day trip.
Return of the Sun (almost!)
Midwinter celebration isn’t just about the swim in icy water, or the magnificent feast and feeling of camaraderie that we all share being on a huge continent that at that time of the year has a population less than a Wallabies test score. (Well not quiet, but we are all still groaning over the last Test against the Lions). Although these are all very important things to us, it also marks the Winter Solstice, or the point at which the Sun has travelled to its furthest point North and will begin to once again slip to the South. For those not technically minded, that means that before too much longer, the Sun will once again pop over the horizon and we will be treated to those things that people in most parts of the world take for granted, sunrises and sunsets.
There had been a few excited people on station taking photos and proclaiming on Facebook that the Sun had returned, for a few days, but these were likely the manifestations of mirages caused through surface inversions, bending the light at the horizon and giving the appearance of seeing the top of the Sun.
But for us at Davis, the official event occurred at 1:34pm on 10th July. Those eager to enjoy the warming (?) rays of the Sun gathered at the Heli hut to pay homage to the golden globe and work on their tan; after all, Davis does have the enviable reputation as being known as the “Riviera of the South.”
Barely had the zinc cream been applied and the mocktails poured when it once again slipped out of sight at 2:12pm. Only 38 minutes, but that was 38 minutes more than we had seen for 6 weeks, with the promise of longer days to come until the Summer Solstice in December when the station will be enjoying 24 hours of sunshine.
Well, there’s a saying back on the mainland that you should never invite a weatherman to a bbq unless you want it rained out, and it appears that in Antarctica you don’t get the weatherman to organise the sunrise party. One eighth of cloud cover and it was exactly where the Sun was due to make it’s appearance. And although the clouds did break briefly to allow a few pics, the sun bathing will have to wait for a later date.
This story was written a little in advance in order to meet the deadline for this week’s Icy News with the plans that were hatched for the day. Simply add photos and “Hey Presto”, instant story. Sure, we could have just dropped the story, or even fibbed a little and told you that that was exactly the way it went down, but integrity is something we pride ourselves on at Davis, and so, the story remains, but instead we will include a few photos taken around dawn (or was it dusk? Never can tell when the sun doesn’t actually rise) leading up to our first rays of sunshine in 6 weeks.
The world is full of coincidences
This week has seen not one, but two birthdays here at Davis. As if that wasn’t coincidence enough, one was the last day without the Sun and the other was the first day with the Sun. One was the youngest person on station, the other the oldest. One is on their first trip to Antarctica, the other likely their last and to top it all off, both were the station sparkies.
Simon has headed up to Whoop Whoop for the week in order to help in the retrieval of some gear from up there, but a combined party is planned for Saturday night to help celebrate this milestone
Big happy birthday to Simon and Colin! Ages won’t be mentioned here, though the picture of Colin with his cake may give his away. (And for the record, he is the one that is the oldest).