When there is morning frost on ground in an open park, whys is it that none is on ground under benches?

Question

When there is morning frost on the ground in an open park, why is it likely that none is on the gorund beneath park benches?

Answer 1

Two objects which can "see" each other will transmit (mainly infrared) radiation to each other at a rate based on their temperatures. On a clear night, the open ground is having a conversation with outer space, which is pretty nippy. It therefore loses much more heat talking to space than it receives from space in the conversation.

The park bench acts like an insulator between the ground and space. The ground directly underneath it is having a "heated conversation" with the bench instead, which is much warmer than space. The ground therefore receives about as much radiant heat from the bench as it radiates to the bench, keeping its temperature from falling below freezing.

Answer 2

One of the causes of frost in the morning, is reradiation. This little quirk of nature is used by folk in the deserts to make ice at night. When the sky is clear at night, heat from the earth will reradiat back out into space. This will cause things to freeze even if the ambient temperature is above freezing.

A park bench blocks this from happening to the ground directly under it.

You can see the same thing happen with a car port. its open on all four sides but has a roof. In the late fall you will see that every ones windows are frosted but not on the car that is under the car port. Same deal.

you will also see the same thing happen to the whole area on a night when it is overcast. The cloud cover will keep the temperature from dropping as a result of this phenomina because it acts like a park bench over the whole sky.

Conversly the coldest nights in winter are the clear ones.

Answer 3

Frost forms on the ground in the open more easily because the ground cools through heat radiating away from the ground to the open sky. The underside of the bench would interrupt the heat being radiated by the ground under the bench and keep that ground a bit warmer.

Answer 4

Frost is the result of the condensation of water vapor in the air due to cooler or cold temperatures. The reason there is frost on the ground, aka grass and dirt, as opposed to the ground below the bench, is because that bench is over top the ground it sits on, protecting it from the water vapor or water droplets that fall from the air above and freeze.

Answer 5

in order to have frost, you must have dew. If there's some sort of cover to keep the dew from reaching the ground, in this case, a bench, the frost can't develope because there is no moisture under the bench to freeze.

Answer 6

The morning frost would probably be on the bench, not under it.

Answer 7

The answers from SAN, john d, and sojsail are right on target. Listen to them.

Most of the others are confused about what causes dew and frost. Some even talked about dew "falling," which is not how dew occurs.

Answer 8

I am guessing it has to do with wind. Blowing wind on the grass would make the water freeze easier. This is a guess.

Answer 9

It's warmer there, and it never reaches dew point, no moisture, no frost.

Answer 10

because its sheltered and slightly warmer under the bench maybe