Facts of the Matter
Transfer of heat is at heart of weather
The transfer of heat from the equator to the poles is the cause of weather. It might manifest as gentle rain, wind, thunderstorms, hurricanes or tornadoes.
It is all ultimately caused by water vapor, which evaporates from the surface, takes heat with it as it rises and releases the heat higher in the atmosphere when clouds condense.
When there is a heat imbalance, or any kind of energy gradient, it will cause movement -- whether it is water flowing downhill, electricity flowing from high to low voltage, or heat flowing from warm to cool.
A steeper gradient creates a stronger flow, just as water flowing down a steep slope flows faster and with more turbulence than water flowing down a gentle slope.
Think of rapids as opposed to a slowly flowing river.
The kinds of changes in storms that are predicted as global temperatures increase are due to an increasingly steeper heat gradient between equator and poles.
As Earth's heat balance gets more and more out of equilibrium, predictions do not indicate that there will be more hurricanes and other storms, as one might expect.
It is not the number of storms that will increase, but rather the intensity of the storms. The results of studies in the field of nonequilibrium thermodynamics can help to understand why.
Most of the seminal work on thermodynamics and entropy was done on systems that were at or near equilibrium. Nature is never in equilibrium, although all natural processes occur in such a way as to achieve it.
The more out of equilibrium a system is, the stronger the gradient, the more organized the structures that form.
Consider a bottle of water sitting on a table. It is in equilibrium since there is no force acting to disturb it.
But remove the cap and turn the bottle upside down. Now there is a strong gravitational gradient that acts to empty the bottle. As a result, bubbles of air surge into the bottle to replace the water that surges out.
This chaotic state is unorganized, as would be the heat transfer on the globe if Earth were not spinning on its axis.
Give the water in the bottle a little circular motion, and the water will organize itself into an inverted tornado.
In the same way, the rotation of Earth imparts a small spin to air and water that causes hurricanes, tornadoes and temperate storms to rotate and organize into the patterns that we see on weather maps.
On the other hand, and seemingly contrary, more tornadoes are spawned by more violent hurricanes. The greater the heat gradient, the more violent the hurricane, the more turbulent the air flow, and the more likely that tornadoes will occur.
There have already been more tornadoes in the first two days of September than normally in the whole month of September.
Of course, statistics are almost irrelevant when it comes to weather, just as in coin tosses. Weather statistics are the basis of climate, which is nothing more than weather averaged over long time periods.
professor of science at Honolulu Community College, teaches earth and physical science and investigates life and the universe. "Facts of the Matter"
is published on the first and third Mondays of every month. E-mail questions and comments to email@example.com