The world is connected by heat that travels by cooling …
At the centre of the earth the solar heating is so great that the only way out for the air at the surface near the equator is to rise up above the tropical currents and be squeezed out over the tropics down to "higher latitudes".
These "higher latitudes" are about 20 to 30 degrees from the equator.
What happens is that between the tropics all the air eventually heats up expanding until it reaches the tropopause. It is ripped away from this height by the mechanics of the moisture in it. The celss of heated air cool. And fall.
Originally posted by OnlineConversion.com:
The nautical mile was based on the circumference of the earth at the equator.
The earth is 360 degrees around.
Degrees are broken into 60 "minutes"each.
There are 360 x 60 "minutes" of longitude around the earth.
This is the basis for the nautical mile.
1 minute of longitude at the equator is equal to 1 nautical mile.
The earth is, by definition, 21,600 nautical miles in circumference at the equator.
The earth is therefore 21,600 "minutes" of longitude in circumference at the equator.
It takes the air 12 to 18 hundred miles to cross the tropics and cool sufficiently to fall down the the surface again.
When it falls it reheats and pushes the air beneath it out of the way.
This displaced air becomes the trade winds. They move south, south west to be more exact. It just so happens that a ship hugging the coast of Africa can sail out to the middle of the ocean from just north of the tropics and pick up these winds and cross the ocean by means of them.
As you can imagine the equatorial current is upward shifting. But the tropical ones can move in a variety of different directions.
In fact interaction with the equatorial currents and the trade winds make sure they regularly unsettle. This interaction is the first appreciable weather.
Something similar happens over the horse latitudes. Some 30 degrees north and south, a similar lassitude allows moist water to rise to the tropopause once again and extend to the north and south jumping over the same sort of distances before falling to earth once again. These currents are far more seasonal.
And because they are less constant they are more erratic.
Actually they behave more according to the other factors that affect weather in a less intense way than solar radiation over the equator. They provide a less stable northern trade route.
Because the maths fits it has become a socially accepted mistake that the spin of the earth provides the rotation of storms.
This is obviously not what is happening when you come to realise that cyclones move not around the earth but around anticyclones.
In the tropics and immediately north of them, the cyclones move east to west. The same way that the trade winds in the region go.
But farther north in the region of the northern trade winds the cyclones move west to east.
What happens in a cyclone is that the main currents in them move up and down. This movement is intensified by the heights the columns reach and by the mechanics of the water they contain.
Huge amounts of heat is evolved and reabsorbed inside them and is the movement of these currents that drive the vortex. It is the same process that causes water to dain in a circular motion from a container.
And it is a process that is easily disturbed.
For all their power, a shearing wind aloft will quickly put an end to them.