Frost On Roof Above Freezing

The phenomenon of water freezing on objects like the ground parked cars motorbikes etc is due to thermal inertia.

Frost on roof above freezing.

Frost is a thin layer of ice on a solid surface which forms from water vapor in an above freezing atmosphere coming in contact with a solid surface whose temperature is below freezing and resulting in a phase change from water vapor a gas to ice a solid as the water vapor reaches the freezing point in temperate climates it most commonly appears on surfaces near the ground as fragile. A lack of frost can indicate that heat is leaking out through your attic space onto the roof and melting the frost. So how did ice form on the roof the frost on the car effect is not just due to temperature inversions. On a long cold spell these objects will cool down to below 0 celsius.

The kentucky mesonet recently added some extra temperature sensors at varying heights that show just why this could occur. 1 initially the air and the car are at temperature 37 f and the dew point is 35. Something i implied above but didn t say explicitly is that when frost forms on the roof the roof is below freezing. Low temperatures overnight were generally in the.

Ice at least at atmospheric pressure cannot form above the melting point of water 0 celsius. As it cools below 35 degrees water condenses on it. Something i implied above but didn t say explicitly is that when frost forms on the roof the roof is below freezing. That is how we get a frost without a freeze.

In other words the sequence might be as follows. Have you ever wondered why frost can form on nights when the temperatures only fall to 36 or 37 degrees. The plot below shows a 24 hour trace of the temperature measured at 0 5 meters above the ground in blue at 2 meters above the ground in red and at 3 meters above. Mon 06 oct 2008 19 38 20 gmt frost at 35 degrees.

If the dew point is below freezing the water vapor condenses as ice freezing as frost. We had a chilly start to the day with frost in many countryside locations. So ice can form even if the temperature of the surrounding air is above freezing. The radiative cooling effect is strong enough to lower the temperature of surfaces exposed to the sky by several degrees below the ambient air temperature.

In other words the sequence might be as follows. Does your garage have a frosted roof and the rest of your home does not or vice versa. 1 initially the air and the car are at temperature 37 f and the dew point is 35. 2 the car roof cools radiatively.