|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.