This was taken from Housesteads, looking towards Newcastle. The cloud in the middle spreads flat across to the left. Not quite the typical incus cumulonimbus anvil shape but not bad. I had an idea that it was caused by convection hitting a temperature barrier and being forced sideways. A bit of research has revealed that in the layer of air closest to the Earth which is called the troposphere, the temperature of the air does fall with height. The measure of this is called the lapse rate, in degrees Celsius per km. Hence convection works because the sunlight warms the ground and the ground warms the surface layer of air. This expands, becomes less dense and floats upwards. I teach that it will then cool, shrink, become more dense and sink. But I'm thinking about how the bubble of warm air will lose the internal energy needed to lower its temperature. How efficient would conduction be? Is it through adiabatic expansion? But the next detail I learned is that temperature goes the other way in the stratosphere, the next layer up. It is coldest where it butts up against the troposphere and then warms up as you increase in altitude. This would put a stop to convection and is why clouds spread sideways. But is the cloud in the picture really tall enough to be at the top of the troposphere? That would be 10km up. Hard to judge. I should have measured the height of the aeroplanes with my little finger method.
