Why is it colder at sunrise?

Question

I always find it is really cold just before & during sunrise. Can anyone explain why this is? I figure that the sun warms the air and the hot air rises and it pushes the cold air down to the ground making it colder. Once the sun rises fully it warms the lower colder air. Am I just talking crazy talk or does theory seem correct, partially correct (or completley insane!!!)?

Answer 1

That's about right.

When the sun is up it heats the ground and atmosphere so you get the hottest time of day around sunset, this isn't strictly true because of wind chill etc.

When the sun is down, the ground radiates the heat it has absorbed and so will be it's coolest just before sunrise.

Answer 2

I'm not sure if your correct but your theory sounds really good.  I would think that you are probably right around the right answer or right there.  Good Think!!!  Intelligence is your only true freedom!

Answer 3

Your observation is correct in that the coolest time of day is usually just before/at sunrise.

On a clear night with light wind, the earth continues to cool all night due to the absence of solar radiation. If the ground is cooling all night, it would only make sense that the coolest moment would be the last possible moment: just before the sun breaks the horizon and begins warming things up once again.

There are weather events that prohibit radiational cooling from taking place completely, such as: cloud cover (greenhouse effect), high winds, or being under the influence of a warm frontal system (where it is not uncommon for the temps to rise overnight).

On the contrary, maximum heating typically takes place in the late afternoon before the sun begins setting. The precise time of day this happens changes with the seasons (later in the summer, earlier in the winter). However, a cold front passing through midday can make it so you have your max temp in the morning and then turning colder in the afternoon. There are always variables and exceptions to the rule.

As far as your reasoning behind max cooling, you're not completely off at all. During radiational cooling, the warm air does leave the surface and the surface cools. With cool air staying low, as cooler air sinks, there is usually what's called an "inversion" set up at around 1,000 feet altitude. An inversion is a layer of warmer air aloft, above a cooler layer below it. It stabilizes the atmosphere.

This is why FM radio reception can be so lousy in the early morning. The radio waves bounce off the inversion.

Good observation!

Answer 4

you mean its colder in sunrise compared to mid day? of course ! sunrise is closer to nightime. what i mean is that ,during nightime the temperature is lower than during daytime. now , at sunrise the temp at night still prevails because the sun is still about to shine, and still not gained full strenght.

Answer 5

because the roads remain empty and in the winter the sun melts the mist

Answer 6

I would have thought it is something to do with the cold air at night that hasn't seen sunlight for a fair few hours. With sunset the sun has been out and shinning all day so air temperature is warmer, but as nigh-time sets in the air cools and has to get warm again as the sun rises.

Thats what I think anyway!