30 years old and still don’t fully understand!
In: Biology
Basically upper level clouds rub together and produce static electricity similar to how rubbing your socks on carpet lets you shock people. Eventually that static builds up enough to produce bolts of lightning. The heat from that lightning causes the air in the vicinity to heat up at an explosive rate, causing a pressure wave. That pressure wave is the thunder you hear.
Why does it happen more often in some places than others?
Air heated at ground level by the sun rises up and forms into clouds of ice and water droplets. These, bumping around against each other causes a buildup of static electricity in the clouds, which is released as lightning. The lightning super-heats the air, which rapidly expands then contracts again, causing a shockwave we hear as thunder.
Summer ones at the end of a humid day are bc the sun heats the ground which raises the air but that air is really hot and humid and carries all of it up very high and quickly too. You’ll see those big bulging clouds forming as it condenses high up. That condensation is unstable and forma storms on the spot, rains down and Cools everything off. The thunder etc someone else explained.
Hot air rises. When air rises it cools down, but humid air cools less quickly than dry air. So warm moist air that finds itself rising into dryer air will end up even warmer than its surroundings, so it will keep rising and rising. This is called an unstable atmosphere.
Humid air, when it cools, will have that humidity condense as water droplets. When a gas becomes a liquid it gives off heat (think of it like boiling in reverse, where you add heat to make it go from liquid to gas).
Now you have warm humid air that’s rising, keeps rising ever faster because it it’s warmer than the surrounding air, _and_ is being heated by all the water condensing out of it. That warm humid air that started this whole thing keeps moving upwards, and it brings more warm moist air up behind it.
Some of those water droplets merge with others to become big rain drops, but they can’t fall yet. The speed of the air rushing upwards is enough to keep them suspended in air. For now. The amount of rain drops suspended will keep increasing, and eventually that air rushing won’t be enough to hold them up. But while they’ve been up there they’ve been getting cold. Very cold. Maybe even frozen. When that updraft isn’t enough anymore the rain starts falling, all at once. And it’s cold rain, and that cold takes away the one thing that powered the updraft – heat. And so this powerful engine that had been pumping hot air upward gets shut down abruptly, and all that rain and now cold air comes crashing out of it in one giant solar – a down burst of rain and wind, sometimes called a microburst.
While all this rain and wind were bouncing around up high they made static electricity. Air isn’t particularly conductive so that electricity can’t equalize right away, so it builds up and up and up. Eventually there’s enough there to build a bridge to the ground, and that electrical bridge once made, makes it much easier for the rest of the electricity to follow. At the speed of light. All that electricity in a tiny little line of lighting makes for a ton of heat. Heat gets the air molecules moving quickly, so they radiate outwards like a little explosion – thunder.
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