Friday, 26 April 2013

Our Old Friend The Jet Stream

That's the British summer over then, enjoy it? The British weather is excelling itself this week, ice cream and sleeveless on Monday, mushroom soup and a big coat on Friday.
As usual, it is our old friend the jet stream that's to blame, the same thing that ushered in a severe drought which triggered stern drought warnings by the Environment Agency last year and then several months of torrential rain produced widespread flooding.
It all makes our weather very unpredictable which is making the weather forecasters job a bit of a nightmare as the huge fluctuations make a mockery of any long range forecast.
All Meteorologists agree that the Jet Streams behaviour has changed dramatically in the past few years and has produced these lengthy bouts of extreme weather but why has the jet stream changed its behaviour, meandering more frequently where before it stayed relatively stable and slowing down and speeding up, trapping regions of high or low pressure over the same part of the globe?
The MET Office say the most likely culprit is the warming Arctic where temperatures have increased at more than twice the global rate resulting in the disappearance of 1.3m square miles of sea ice.

Here's the science bit, the air in the tropics is warmer than the Arctic and it rises. As a result, the atmosphere there is higher than it is over the Arctic and gradient is created and air slides down this atmospheric hill towards the Arctic. This flow of air, high up in the atmosphere, from the tropics to the Arctic, creating the jet stream.
The world rotates from west to east, however, and that rotation whips up this northward flow of air that descends over higher latitudes and sends it flying east round the globe as the jet stream. Until recently, this mighty stream of air flew round the planet, in a slightly wavy path, between 30 and 60 degrees north. The trouble is that the gradient between the atmosphere in the lower latitudes and in the Arctic is being disrupted and as the Arctic heats up disproportionately, so does the atmosphere at the north pole and as it warms up, it rises. The effect lessens the gradient between the tropics and the Arctic so less air pours down towards the north pole and less air is whipped up by Earth's rotation to form the jet stream and the jet stream slows and meanders up and down.

Professor Piers Forster of Leeds University warns: 'I think it is too early to say that climate change is definitely involved. The evidence suggests it might well be but we need more studies to confirm the link'.
And here was me thinking that climate change was all about governments wanting to raise green taxes in an unholy alliance with climate scientists wanting to grab more research grant money. Kinda throws a spanner in the works of the climate change deniers conspiracy theory when the climate goes all wonky and the things environmentalists and scientists have been warning about for decades comes true.

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