Convection?

[Cheviotranger]

Hi

I am wondering whether there is any difference between normal convection heating air and thermal convection?

Regards

[chrisbell-nottheweatherman]

Hi - I'm still very much a beginner myself, but my understanding is that warming air causes convection rather than the other way around. Most of the time, heating is caused by the effect of sunlight warming the ground and therefore the air close to the ground. That warm air rises in the same way a hot air balloon does, and will keep rising until the temperature of the rising air drops to the same temperature as the surrounding air, at which point it will stop rising.

In conditions where the atmosphere is cold at upper levels and relatively warm at lower levels (i.e. a steep lapse rate) the rising pocket of warm air will rise rapidly and will keep going for longer as the temperature of the air around it will be dropping rapidly. Although the temperature of the rising pocket will also drop as it ascends, if the lapse rate is steep enough, the temperature around it will be dropping at least as quickly, so the temperatures don't equal out until the rising air has risen a long way and cooled substantially. If the pocket of air is moist, its temperature may drop below its dew point, i.e. the relative humidity of the air hits 100%. It can't hold any more moisture, so that moisture starts to condense, forming clouds and precipitation.

This explains why thunderstorms associated with heavy, showery downpours occurr most frequently happen either during the summer when strong sunlight heats the ground significantly, or during winter or spring when weaker ground heating is combined with very cold upper air. In both cases a steep lapse rate is formed.

No doubt one of our experts will soon correct me and provide a more detailed explanation, but that's my take for what its worth.

Edited January 27, 2010 by chrisbell0033944

[Cheviotranger]

Hi Chris

Thankyou very much for your reply!