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Highway & Road Deicer Consultant & Expert Trainer
Expert Advice on Pavement Temperature vs. Air Temperature
Typically pavement temperature will move similar to the air temperature and normally with some thermal lag.
The curve usually looks like the following diagram with the air temperature changing often rapidly, while the
ground temperature follows.
Some exceptions to this are
This is an idealized diagram
and it should be noted that
several factors can and do
significantly affect the
pavement vs. air temperature
The two most significant are
subsurface or ground
temperature and the presence
or lack of solar radiation.
The subsurface – if the
subsurface is warmer or cooler
than the air and pavement it can affect the air-roadway temperature relationship. Two examples:
1. In the fall, the subsurface is still above freezing when the air temperature is below freezing. The reason is that
often during these conditions, the cooler air temperature cannot remove enough heat from the roadway surface
and the subsurface to drop the pavement below freezing. The pavement is drawing heat from the subsurface.
2. In the late winter or early spring the subsurface temperature is often below freezing while the air
temperature is above freezing. In this case the air cannot transfer enough heat to the pavement to offset the
colder subsurface. This is especially true with the reduction of solar radiation such as cloud cover and/or
Solar radiation –The effect of sunshine can significantly affect the pavement temperature depending on the time
of year, cloud cover, shading from vegetation, and the color of the roadway surface. Typically, the darker the
roadway surface color the warmer the surface temperature will become. Without the presence of shade, sunshine
at times can raise the pavement temperature significantly above the ambient air temperature. Three examples:
1. In the summer under bright sunshine and no shading pavement temperatures can be much warmer than the air
temperature, especially if it is new asphalt and is very dark in color.
2. In the winter, bright sunshine on a pavement surface when the air temperature is slightly lower than freezing
can raise the pavement surface temperature to above freezing.
3. In the winter, the angle of the sun and the presence of cloud cover can prevent the sunshine from reaching the
roadways surface. This allows the air temperature to rise while the roadway surface stays cold. This explains
why the air temperature can be above freezing while the roadway surface temperature is at the freezing point of
Pavement Temperature vs. Air Temperature
by Dale Keep, Highway & Road Deicer Consultant & Expert Trainer