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23 Degrees team Colorado update: thermals and paragliding

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Stephen Marsh Stephen Marsh | 08:30 UK time, Friday, 8 July 2011

Distance travelled ~ 486'259'200 km: day 189

Back on day 161 Helen and the 23 Degrees team ventured to Colorado to study and film thermals, another complexity of our atmosphere.


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When sunlight hits the surface of the Earth it’s absorbed by the ground, and then radiated back up into the atmosphere as heat. This heat warms the air above it, which expands and becomes less dense than the surrounding cooler air.  The warm less dense air rises in what’s called a thermal column. And it’s these thermal columns that support the Paraglider carrying it up into the sky.
Thermals are a bit of a free lift, and many birds have evolved to use them to travel huge distances without expending energy by having to flap their wings. Thermals tend to be stronger in the afternoon when the earth has absorbed enough solar energy to heat the air above it.  

Thermals reveal on a small scale what’s happening to our climate across the Earth because they create a heat gradient between hot and cold air. While warm air is rising, cooler, denser, air flows in to replace this rising column of warm air, until it is also warms, becomes less dense and starts to rise. This action causes the atmosphere to be in a continual state of flux, with warm and cool air moving up and down and horizontally. This constant movement of air transfers energy within the atmosphere and it is this process that drives weather. 
Heat gradients form the basis of all weather on planet Earth because nature hates gradients. It likes balance so if one part of the planet is getting more solar energy and heating up the atmosphere, creating a heat gradient cooler air will rush in to cancel it out.  And this movement or air getting rid of heat differences in the atmosphere that generates huge weather patterns powering events like thunderstorms, Tornadoes and even snowstorms



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