Why is it the coldest temperature right as the sun is coming up as opposed to 12- 3 am when its the darkest?
In: Other
The amount of heat reaching the ground from the sun is very close to zero from sunset until sunrise. Once the sun is fully above the horizon the average heat from solar radiation increases smoothly until noon and then decreases in the same way but, once the sun is fully below the horizon, the heat drops to practically zero. This means the temperature keeps decreasing until at least sunrise, on average.
Imagine you put a glass of water into the fridge for 1 hour, and then take it out. When is it the coldest? It’s not in the middle of the hour, it’s right before you take it out of the fridge.
So, the temperature is the coldest just when the sun is about to heat up the place.
While you might think the coldest time of the day is before the sun rises, it’s actually about 30 minutes after that happens. That’s because the radiation from the sun isn’t yet strong enough to exceed the amount of heat being radiated by the earth.
The Earth is losing heat to space constantly.
Until the sun comes up it’s been losing heat constantly through the night without getting more from the sun. Thus it has the minimum amount of heat just before the sun rises.
The way I picture it is as follows: imagine the Earth is a glass, and the current “heat” of the Earth is the water in the glass.
The Earth constantly dissipates heat into the atmosphere : there is a hole in the bottom of the glass from which water drips out.
The Sun heats the Earth: it’s adding water into the glass to fill it up.
When the sun is very low over the horizon, it fills the glass more slowly than the glass is being emptied by the hole at the bottom. When the sun is reasonably high over the horizon, it fills the glass more rapidly than it is being emptied by the hole.
So essentially from the end of the day, the glass starts emptying, getting more and more empty through the night and indeed continuing to empty for a while after sunrise, at which point the level is at its lowest before the sun tops it up and the process restarts.
Latest Answers