Tonight there was a lecture by a French group which uses balloons to study the stratosphere. They fill large, thin balloons with helium, attach a bunch of instruments and launch them into the atmosphere to a height of about 20 km (~60,000 ft). The balloons fly at an altitude where their density equals the density of the air around them - if two things have the same density neither will sink or float they will just stay there. These balloons will then travel in an air mass collecting data for up to three months. By putting these balloons up there, this group is hoping to get more information about ozone depletion, how waves travel through the atmosphere and how cold air that gets trapped near Antarctica mixes with warmer air from the north.
This group has launched a number of balloons so far and they have a quite a few more to go. I saw one of the balloons as it was released. It was pretty cool. When it is launched it looked almost empty, but when it gets to its maximum altitude it is a perfect sphere.
Ozone Hole
The basic idea is this...the atmosphere is broken into different layers. Each layer is defined by how the temperature changes. In the troposhere, the lowest layer where we live, as you go higher the temperature decreases. In the stratosphere, the second layer, as you go up the temperature increases. In the next layer, the temperature decreases and the top layer the temperature increases again.
Except for the ozone that is created by pollution in the troposphere, the majority of the ozone is found in the stratosphere. This is the famous ozone layer and where the ozone hole occurs. Ozone absorbs much of the UV light that comes in from the sun which protects life on Earth (this is also why the temperature increases in the stratosphere).
In the austral winter (winter down south, our summer), it is obviously very cold. This cold air gets trapped in a vortex in the atmosphere. Basically, there is a huge mass of very cold air spinning about Antarctica during the winter. This air is trapped it cannot get out. So then comes pollution, especially CFCs (chloroflourocarbons), these also get trapped in this vortex. Once the air starts to warm up and sunlight hits it again, the CFCs react with the ozone which destroys the ozone. The chlorine from the CFCs break off and attack the ozone.
The presenter showed us a before and after picture of ozone levels from this year. It was remarkable to see a normal level of ozone and then a month or so later, the ozone was gone. There was an international treaty to limit the use of CFCs, according to the presenter these probably won't have a significant impact on the ozone hole until about 2030. This is simply because it takes so long for the CFCs to make their way from wherever they are created to where they cause damage.
2 comments:
In the early 1900s, the first balloon was sent into the sky which could record data. In the 1920s, some sort of radio thing was figured out which automatically transmitted data. Now they use satellites. A signal is sent from the balloon with all the data, there is also a GPS aboard so they know where the balloon is.
When the balloon dies, they do not recover it. There is some mechanism to cut the balloon from the instruments, I imagine that they would retrieve the instruments whenever possible.
After the balloon is cut, it is lost. It doesn't seem to environmentally friendly, does it?
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