Wednesday, 9 October 2013

Convection on the Wall

 
The clouds above the Tyne Valley are typical cumulus clouds. During the day, the Sun heats the land. The air above the warm earth expands and becomes less dense. It floats upwards. There is a certain amount of water vapour in air - usually so little that you don't notice it. However, when the air gets cold, the amount of water vapour that can be held without noticing it decreases. As the warm air rises, it cools. We say that the vapour becomes saturated because the cold air can hold less water vapour. Some water vapour condenses out into water droplets and a cloud forms - all because convection warmed air and sent it upwards to cool.
 
Another thing I noticed is this lovely old barn. I suspect that the idea of it was to put cattle in the left-hand side so they were safe from raiders, but also that you might sleep above your cattle. They are large portable heaters who would heat the air down below and the warm air would rise to heat your room above. A bit smelly perhaps. I've always imagined that this is the case with this barn but if anyone knows differently, please let me know.