Why the Weather Changes

Dear Tom,
Why does the weather change?
Dorrease Williams
Dear Dorrease,
The unequal application of heat energy to the Earth's atmosphere drives
weather changes, and almost all the energy that fuels the weather comes
ultimately from heat energy contained in sunlight.
Because the Earth is a sphere whose polar axis is approximately
perpendicular to the sun's rays, its equatorial regions receive much more
heat from sunlight than do its polar regions. Therefore, the Earth's
equatorial regions are warm and the polar regions are cold.
It's crucial to the explanation to realize that warm air is less dense,
relative to cold air. Air density differences established by temperature
contrasts drive global wind patterns that attempt to equalize atmospheric
density differences and reduce temperature contrasts. The ongoing interplay
of warm and cool air masses causes what we refer to as "the weather."