Understanding radiation cooling makes a lot of sense (Part 1)

When I looked at the weather forecast, it said, "Tomorrow morning, it will get very cold due to radiation cooling."
I often hear words like this.
However, few people other than weather forecasters can fully understand the meaning of this word.
I think the number is quite small.
First of all, there is a website that clearly illustrates the meaning of this word.
Let's take a look at that.
http://www.jma-net.go.jp/matsue/chisiki/column/phenomena/radcooling.html
In the first place, radiation is like gravity or magnetic force, and it occurs no matter how far apart two objects are, even if there is a vacuum between them.
This represents the transfer of heat in the form of electromagnetic waves.
Thermal energy flows to cold objects (things that can be seen with the naked eye).
When the outside temperature is 0°C, most things outside will also be 0°C.
However, the average temperature in the vast expanse of space is about -270°C, which is almost absolute zero.
It's a cryogenic world.
If there are clouds, the upward radiation exchange between the ground object and the clouds will occur.
It doesn't cool that much. However, on a clear day with no clouds, the radiation exchange is
This is an exchange with the vastness of space and the extremely low temperatures. Naturally, the temperature is rapidly lost.
This is why the term radiative cooling is used when there are no clouds even in summer.
Understanding this can help you solve the mystery of a common phenomenon that occurs all around us.
In winter, if you leave your car outside without a roof, the top of the car, including the glass, roof, and hood, will be exposed.
There will be almost frost.
However, if you keep it under a roof, frost will form on the roof but not on your car.
It's common knowledge that even children know, but few people can explain why.
This can be explained by radiative cooling.
In principle, if you place it in the same outdoor temperature, it will be the same whether it is on a roof or a car.
It must be the temperature. Frost is condensation that freezes, so
For this to happen the surface must reach the dew point.
If condensation occurs on the roof but not on the car, the roof is the better.
The temperature is lower than that of the car.
There is a contradiction in the fact that they are the same temperature when placed under the same outside temperature.
The key to resolving this contradiction lies in radiation.
If there is a roof, the roof exchanges radiation with the universe, and the car exchanges radiation with the roof.
The temperature of the roof is about 0℃ at most.
Cars lose very little heat through radiative cooling.
On the other hand, the roof is cooled by radiation from the -270°C temperature.
Of course the temperature will drop significantly.
This solves the mystery of why frost doesn't form on your car when you have a roof.
It may be a little difficult, but did you understand it?