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What is the Air Pressure Belt & the Earth’s Wind Belt?

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Definition of the earth’s air pressure belt

Weather-related high and low pressure areas in the atmosphere are not locally bound, but their formation tends to be global in terms of their geometric expansion. In very specific regions of the earth’s surface, high and low pressure areas of different intensity and size form at certain time intervals. This phenomenon is known as the earth’s air pressure belt.

Definition of the earth’s wind belt

The resulting air eddies in the atmosphere, the dimensions of which can take on continental dimensions, are primarily formed in certain regions of the earth. These air eddies are also not statically bound. The observation shows, however, that in certain areas of the earth the winds that are generated by air eddies always come from similar directions. This natural phenomenon is known as the earth’s wind belt.

Considerations about the Earth’s atmosphere

The earth’s atmosphere extends hundreds of kilometers into space from the earth’s surface. The atmospheric air pressure is greatest on the earth’s surface and decreases with increasing altitude. The individual air particles are set in different movements by various influencing factors, which we want to take a closer look at here. The manner of these movements are by no means similar to the rotation of the earth. But they have their indirect cause in the earth’s rotation, in the alternation of day and night and in the intensity of the solar radiation.

Effects of the earth’s rotation

The earth rotates around an imaginary line, the earth’s axis, which runs through the north and south poles. As a result of this rotation, every body on the earth’s surface experiences a peripheral speed. This circumferential speed is greatest at the equator, decreasing more and more with increasing latitude until it finally becomes completely zero at the earth’s poles. If a body moves from near the pole in the direction of the equator, it comes from zones of lower circumferential speed to zones of greater circumferential speed, even if this change of location takes place at constant speed. The body experiences a Coriolis acceleration and the associated Coriolis force (named after its discoverer, Coriolis).

Mathematically, the Coriolis acceleration is defined as:

a c = 2 * v * ω

In it is

a c is the Coriolis acceleration,

v is the relative speed from the earth’s axis in the direction of the equator,

ω is the angular velocity of the rotating earth.

It is easy to see that the Coriolis acceleration and thus also the Coriolis force is only present when the relative speed v has a value other than zero.

Effects of solar radiation

Solar radiation is greatest during the day near the equator. As a result, the warm air rises at the equator. The upward movement of air inevitably causes a flow of neighboring air layers that come from areas with greater latitudes of the earth. This means that the inflowing air masses close to the earth must pass through zones of different circumferential speeds of the earth. This means that these air masses are inevitably exposed to a Coriolis force during their movement, through which they experience an additional lateral deflection in an east-west direction.

Changes at high altitude

The air masses rising in the equatorial zone cool down again at great heights and thus sink back towards the earth. In the area of ​​the earth’s surface, these air masses heat up again and the same process is repeated. The constant air vortex in the subtropical equatorial zone extends approximately over an area from 30 ° north latitude to 30 ° south latitude. In the entire Äuatorbereich thus creates a low pressure area around the entire globe.

Three large areas of opposing air circulation for each hemisphere

In the equatorial area in the northern hemisphere, air currents from the north-east, which are also called north-east trade winds, circulate. The range of action of these northeast trade winds extends to about 30 ° north latitude. In the southern hemisphere we find mirror-image air currents from the south-east, which are known as south-east trade winds. Their range of action extends to about 30 ° south latitude.

In areas that extend around 30 ° to 60 ° north latitude and also around 30 ° to 60 ° south latitude, air circulations in the opposite direction to the trade winds from the equatorial area now occur.

In areas from about 60 ° north latitude to the North Pole, large rotating air currents, the polar easterly winds, are formed. In mirror image, the same thing happens here in the southern hemisphere from about 60 ° south latitude to the south pole.

Symbolic representation of these rotating air masses

The rotating air movements of these three described areas in the northern and southern hemisphere are roughly comparable to oversized gears that are in mesh with one another and therefore always rotate in opposite directions. Of course, these rotating air vortices are not locally bound statically, but they move within a certain framework depending on the weather development. However, the prevailing wind directions do not change significantly throughout the year.

High pressure and low pressure areas

In the polar regions there are always areas of higher air pressure, i.e. high pressure areas. Low pressure areas are always to be found close to the equatorial area. This is related to the warm air flow rising from the ground, which is caused by the strong solar radiation. In the latitudes in between, the rotating air gyroscopes, which often assume almost continental dimensions, often alternate between a high-pressure and a low-pressure area.

Conclusion

Air pressure and wind belts of the earth are essential components of the very complicated meteorology. Even in the computer age, it is not yet possible to create a reliable weather forecast over a longer period of time. This underlines the high complexity of many influencing factors on the global weather system.