WATER AND SOLAR REFLECTION /
ABSORPTION
METEOROLOGIST JEFF HABY
The earth is covered with 70% water thus the amount of solar reflection and
absorption has a profound influence on the global temperatures. What is interesting
about water is how variable the amount of reflection and absorption is. Whether the
water is liquid or solid has a significant influence. The sun angle is a prime
determinate in how much reflection and absorption take place. The concept of
reflection is explained through albedo. Albedo is how reflective a substance is. A
substance with a high albedo will reflect a high percentage of the solar radiation
striking it. A 100% albedo (highest albedo possible) would be all the solar radiation
being reflected away. A 0% albedo would mean none of the solar radiation is
reflection and thus all is absorbed into or transmitted through the substance.
First we will examine sun angle. When the sun is low on the horizon (low sun angle)
more radiation will be reflected off water (especially if it is ice). A low sun angle has
a more difficult time warming water because a great percentage of the solar
radiation is reflected away. This dramatically changes though as the sun climbs
higher in the sky. When the sun is directly overhead the liquid water will absorb
just about all the solar radiation striking it. This adds an enormous amount of heat
energy to the tropical oceans since the sun is high in the sky. The tropical oceans not
only get a denser amount of solar radiation striking it but more of that solar
radiation is absorbed as compared to polar ocean water.
Next we will examine whether the water is liquid or ice. Ice acts like a mirror to
incoming solar radiation when the sun angle is low. Less solar radiation is absorbed
by ice than into water given the same sun angle. In the polar areas the sun angle is
low and some of the land and ocean surface is covered in ice. This is a reason why
the polar areas are cold- less density of sunlight and what does get through has a
great percentage of it reflected away. The polar liquid oceans are much warmer
than the ice covered surfaces since liquid water will absorb more solar radiation.
One consequence of global warming is that the reduction in the ice caps results in
more liquid water which in turn results in much warmer temperatures. It is the
polar areas that will by far warm the most when global warming takes place since
polar ice will be replaced by land and water.
In conclusion, the state of water (liquid or ice) and the sun angle have a significant
influence on the amount of reflection that takes place. More reflection takes place
when the sun angle is low and when the surface is ice while less reflection takes place
when the sun angle is high and the water is liquid.