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What are Planetary Winds? How are they classified?.
Planetary Winds
The winds that flow throughout the year from one latitude to another latitude because of latitudinal differences in the air pressure are called planetary winds. They are also called prevailing winds. Planetary winds blow from a single direction over a specific area over the earth.
The areas in which the planetary winds meet are called convergence zones. They generally blow east to west rather than blowing north to south. This usually happens because the earth’s rotation generates the Coriolis effect. The Coriolis effect makes wind systems twist anticlockwise in the Northern hemisphere and clockwise in the southern hemisphere.
Planetary winds also known as permanent winds and are being controlled by the pressure belts, located at the lower part of the atmosphere and blow towards the same direction throughout the whole year. In other terms, they are also called primary winds or prevailing winds. They blow in the direction from high pressure to low pressure. The planetary wind is of three types namely, - the trade wind, the westerlies and the polar wind.
Types of Planetary Winds
In the planetary wind system, there are three main types of planetary winds - The Trade Winds, The Westerlies, and The Easterlies.
The Trade Winds
The sun''s rays fall vertically on the equator which causes the air to heat up, and it rises upwards. Due to the low upward pressure, the rising air has room to expand, resulting in cold and dense air. Due to the warm air on the ground, the cold air could not go straight down. As a result, air travels north and south through the upper atmosphere. At altitudes up to 30°, some of this air comes down and blows towards the low-pressure belt on the equator. This part of the air is known as the trade winds. According to Ferrell''s Law, trade winds blow from the northeast in the northern hemisphere and from the southeast in the southern hemisphere. They are called tropical easterlies as well.
The Westerlies
Some of the air from latitude 30 ° blows toward the poles on the surface of the earth, reaches latitude 60 ° and is then exposed to the cold, dense air coming from the poles. In comparison, warm, light air from the tropics rises above the dense, cold polar air and blows partially towards the polar low-pressure belt; this wind is called westerly wind. It blows from the southwest in the northern hemisphere and from the northwest in the southern hemisphere. Due to the large land area in the Northern Hemisphere, there are some local changes in air movement. However, in the Southern Hemisphere, the largest area is covered with water, so you can move unimpeded by the westerly wind. Westerlies speeds reach their highest between 40 ° S and 50 ° S. This area is called the Roaring Forties and the movement of air is known as Brave Westwinds.
The Easterlies or the Polar Easterlies
The polar easterlies are the dry, cold prevailing winds that blow from the high-pressure areas of the polar region and south poles towards low-pressure areas within the Westerlies at high latitudes. Cold air sinks to the poles, creating high pressures that allow the air to escape south (north of the Southern Hemisphere) toward the equator. They are very cold winds that do not cause rainfall. These prevailing winds then blow from east to west, as this outflow is diverted west by the Coriolis effect. The wind comes from the east, so it is called the easterlies. Unlike mid-latitude westerlies, polar easterlies are often weak and irregular.
POSTED ON 18-07-2022 BY ADMIN
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