The three wind patterns of the Earth
- 12 April 2017 | Windsurfing
What are the major wind systems of the world? Are there specific global wind patterns for different regions of the Earth? What is the behavior of the wind belts that travel the planet?
The wind is the result of an interaction between the sun's energy and the Earth. But our planet is not uniform - land and water are distributed unevenly.
The unequal heating of the surface of the planet, i.e., the temperature differences between the Equator and the Poles, combined with the Earth's rotation is responsible for the creation and development of six major air circulation patterns, three in each hemisphere.
They are the Polar Easterlies, the Prevailing Westerlies, and the Trade Winds. Each one of them rules roughly 30 degrees of latitude, like wind belts around the Earth.
Because it receives the sun's most direct rays, the Equator has the globe's warmest temperatures. On the opposite ends, the two Poles receive the most disperse radiation, i.e., extremely low temperatures.
So, there's high-pressure on the Poles (cold air) and low-pressure on the Equator (warm air).
What happens is that hot air in the Equator rises and moves toward the Poles, while the cooler air at the Poles sinks and travels toward the Equator creating a continuing wind system.
As Earth rotates from west to east and the Coriolis Effect kicks in, the winds on the Northern Hemisphere curve to the right, and the winds on the Southern Hemisphere curve to the left.
Generally, prevailing wind patterns around the world are westerly - going from west to east - so, for example, in the United States, it's not unusual for California weather to be headed in a few days to New York.
So, how do these huge wind belts form and move? Let's observe the formation of wind patterns in detail.
The wind typically moves from areas of high pressure to areas of low pressure. So, the first air current moves from 90 degrees (North Pole and South Pole) and heats up quickly at 60 degrees (northern and southern hemispheres) - the air expands, rises, and cycles back in a counterclockwise loop. These are the so-called Polar Easterlies.
An identical process occurs between the Equator line (0 degrees) and 30 degrees (northern and southern hemispheres). These are the so-called Trade Winds.
But because between 30 degrees and 60 degrees the air gets trapped, a new convection current begins to take shape, this time in clockwise mode. These are the so-called Prevailing Westerlies.
The wind doesn't go across the equator very often. It's almost like a no-wind zone. Sailors call it the "doldrums."
But sailing problems also take place in the area between the Prevailing Westerlies and the Trade Winds zone, about 30 degrees north. In the past, sailors would get weight out off caravels by dumping horses overboard, to try to travel faster. That is why 30th parallel north ended up being called the Horse Latitude.
Last but not least, the collision between the Polar Easterlies (high-pressure air) and the Prevailing Westerlies (lower pressure air) forms a fast, powerful wind that moves from the west to the east - the Jet Stream.
The Jet Stream moves in a swirl pattern and changes on a daily basis. It is responsible for the transportation of weather systems.
All six wind patterns travel north in the northern summer, and south in the northern winter. However, because there are higher temperature differences and more landmass in the northern hemisphere, the regions located north of the Equator observe more extreme wind currents and weather events than the southern hemisphere.