Dr. Alley: (SINGING) Somewhere over the rainbow, raindrops fall. Sun and rain make a rainbow with your eyes in between, that's all. Sun falls straight on the equator, just skims the poles.
So tropical heating is greater. Air rises and sinks in rolls. Air lifted in these currents great expands as it feels lesser weight, brings cooling. Air cooling holds less H20, condenses to rain, clouds, or snow. That fall, no fooling.
When there's evaporation, it takes energy That is why perspiration drying cools you or me. Equatorial evaporation stores solar heat that's released by cloud condensation. Energy is conserved, pretty neat.
This heat from Condensation slows. Cloud cooling as it upward grows while raining. But when this air comes down, it's dry and squeezing drives its fever high. And you know from your training.
Three degrees F per 1,000 feet upward, cools and rains. Five degrees F per 1,000 feet downward warms up the downwind plains. Somewhere over the rainbow, raindrops fall.
Sun and rain make a rainbow with your eyes in between, that's all. Wet redwoods, cold sierra high above Death Valley set to fry. That's why.