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Heat Islands and Snow Storms

January 5, 2014

Temperatures are often a few degrees higher in cities
than they are in their surrounding rural areas.
This temperature discrepancy is the result of a
phenomenon known as the Urban Heat Island effect.

~~~~~~~~~ CLICK WITH MOUSE TO ENLARGE ~~~~~~~~~~~

Snow Storm Jan 5_ 2014

Snow Storm Jan 5_ 2014

Objects (buildings) can and do absorb and reflect light.
The color of an object depends on what kind of light it reflects.
A yellow object reflects yellow light and absorbs all the others.
When we look at a yellow object, we perceive it as yellow
because it reflects the yellow wavelength of color back to our eyes.

Darker colored objects are excellent absorbers of light.
In fact, black surfaces absorb almost all light.
The sides of buildings, and their roofs, impact air temperatures.

The rate at which an object can reflect solar radiation
is called its “albedo” . The bigger the albedo something has,
the better it reflects radiation.
Everyday asphalt has a low albedo, it reflects radiation poorly
and instead – absorbs it – . It then converts that light
to thermal energy, and emits it back out as heat.

This heat absorption is why the temperature difference
between cities and rural areas is highest
a few hours after sunset.
Cities hold on to more heat for a longer period of time.

Seasons change and Michigan gets all 4 of them.
People really don’t like the idea of a glaring, all white city.
Low-reflectivity colored coating offer an alternative.
These kinds of coatings reflect invisible radiation
without reflecting all frequencies of light .
So, they keep the object relatively cool.

Certain high-reflectivity coatings can also be applied to asphalt.
Asphalt chip seals, and emulsion sealcoats, are two such examples
that treat asphalt to make its surface more reflective.
The processes reduce the albedo factor of asphalt,
which is a major contributor to the urban heat island effect.

Hot summers and ice cold winters make a conundrum or
catch 22 situation for “reflective surfaces in a city”.
Keep in mind the waterways play a big role in reflectivity
and the temperature effect upon land.

UPDATED Snow Prediction Jan 5_2014

UPDATED Snow Prediction Jan 5_2014

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