Pressure And Wind Belt1

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Pressure and wind belts

Atmospheric Pressure, also called barometric pressure, force per unit area exerted by an atmospheric column (that is, the entire body of air above the specified area). Atmospheric pressure can be measured with a mercury barometer (hence the commonly used synonym barometric pressure), which indicates the height of a column of mercury that exactly balances the weight of the column of Atmosphere over the barometer. Atmospheric pressure is also measured using an aneroid barometer, in which the sensing element is one or more hollow, partially evacuated, corrugated Metal disks supported against collapse by an inside or outside spring; the change in the shape of the disk with changing pressure can be recorded using a pen arm and a clock-driven revolving drum.

The atmosphere is held on the earth by the gravitational pull of the earth. A column of air exerts weight in terms of pressure on the surface of the earth. The weight of the column of air at a given place and time is called air pressure or atmospheric pressure. Atmospheric pressure is measured by an instrument called barometer. Now a days Fortin’s barometer and Aneroid barometer I are commonly used for measuring air pressure.

Atmospheric pressure is measured as force per unit area. The unit used for measuring pressure is called millibar. Its abbreviation is ‘mb’. One millibar is equal to the force of one gram per square centimetre approximately. A pressure of 1000 millibars is equal to the weight of 1.053 kilograms per square centimetre at sea level. It is equal to the weight of a column of mercury which is 76 centimetre high. The international standard pressure unit is the “pascal”, a force of one Newton per square meter. In practice atmospheric pressure is expressed in kilopascals, (one kpa equals 1000 Pa).

Wind belts on earth

Inter-Tropical Convergence Zone (Doldrums)

Since air is heated and rises at the equator, a zone of low pressure is formed. This zone is referred to as the equatorial trough. Air moves towards the equatorial trough, where it converges and moves aloft as a part of Hadley cell. Convergence occurs in a narrow zone, called the inter-tropical convergence zone (ITCZ).

It is the belt of equatorial calms and winds lie over the equatorial trough of low pressure. Average location of doldrums is 5°N and 5°S from the equator and this belt lies between two trade winds. As the horizontal pressure gradient is weak, therefore winds are Light and variable.

Because of the convergence of winds, convective activity is dominant. Convection becomes vary strong in the late afternoons carrying warm moist air, often forming huge cumulus clouds, which results in heavy thunderstorms.

Because of the enormous amount of latent heat released by these clouds, the atmosphere becomes hot, oppressive and sultry. Since it is the meeting zone of north easterly and south easterly trade winds, it is also called Inter Tropical Convergence Zone (ITCZ) or doldrums.

Trade Wind Pattern

This belt extends roughly from 5° to 30° N & S of equator. Here, at the surface wind flows from poles towards the equator and in the upper atmosphere, flow is towards the poles. These trade winds originate because of the pressure gradient force from sub-tropical high to equatorial low.  In the northern hemisphere, the trades are north-easterly and in the southern hemisphere, these are south easterly. These winds are regular (steady) and flow in constant direction.

The trade wind belt is also called Hadley cell after the name of the scientist as it resembles the convective model used by Hadley for the whole earth. The energy to derive this cell is believed to come from the release of latent heat during the formation of cumulonimbus clouds in the equatorial region.

The poleward moving winds in the upper atmosphere in this cell begin to subside between 20°-35°N & S latitudes. The subsidence over here may be due to the radiational cooling, because at upper levels it makes the air heavy and at the same time it begins to converge at higher levels over the middle latitudes around 30°. This convergence (piling up) of air aloft increases the mass of air above the surface.

Because of accumulation of air mass at higher levels, it starts descending around 30° latitude in both the hemispheres. This zone of descending air produces sub-tropical high pressure belts and is also known as ‘horse latitudes’ where like the doldrums the winds are light and variable.  

The descending air over the sub-tropical high, is dry and warm. As a result, subsiding air produces clear sky and high temperature. Major deserts of the world like Sahara are located in this region.

 

 

 

 

Subtropical High Pressure (Westerlies Belts)

These lie between 30° and 60°N & S latitudes in both the hemispheres. The winds move from poleward margins of sub-tropical high pressure belts. While moving to higher latitudes, these winds are deflected and become south-westerlies in northern hemisphere and north- westerlies in southern hemisphere. The westerlies of middle latitudes are more variable than trades both in direction and intensity.

These westerly winds are frequently over-powered by polar air masses and cells of Cyclones-2/”>Cyclones and anti-cyclones are formed in these areas. The surface flow of the westerlies may be interrupted by storms and irregular winds blowing from different directions, but in the upper atmosphere these are steady and blow in westerly direction.

The westerlies prevail throughout the year, but are stronger in winter season, especially over North Atlantic and North Pacific Oceans. This is because of the steep pressure gradient from the Aleution islands and icelandic low pressure areas towards the extremely cold continental interiors where the pressure is very high.  

These two semi-permanent lows are the cause of a number of cyclonic storms moving along the westerlies across the globe. In the southern hemisphere, between 40° & 60° latitudes, westerlies are persistent and powerful over water, sailors call them Roaring forties, furious fifties and screening sixties.

Polar Easterlies

Polar easterlies are the winds which move from polar highs towards sub-polar lows. Winds blowing from north pole are not regular. Because the polar high is not considered as quasi (semi)-permanent feature of arctic circulation. However, there are prevailing outflowing winds from the green land.

In winter, the easterly winds are observed from anti­cyclones of Siberia and Canada. The winds in these areas generally blow from various directions and these are largely controlled by local weather disturbances. But on the poleward side of the depressions (cyclones) that form in the northern Atlantic and northern Pacific, the easterly winds do occur.  

The easterly winds in southern hemisphere are well defined and are coherent (semi-­permanent) and regular. Easterly winds blow from the anti-cyclonic systems formed over the plateau of eastern Antarctica. The Indian ocean near the Antarctica experiences such easterly winds.

Little is known about the atmospheric motion at upper levels in high latitudes beyond 70° or 75° (i.e. 70, 80 or 90°) in both the hemispheres due to lack of the meteorological information.

 


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The Earth’s atmosphere is in constant motion, driven by the Sun’s energy and the Earth’s rotation. This motion creates pressure belts, wind belts, jet streams, and other features that shape our weather.

Pressure belts are areas of the Earth’s atmosphere where the air pressure is relatively high or low. The high-pressure belts are located at the poles and the low-pressure belts are located near the equator. The air in the high-pressure belts is sinking, which causes it to warm and dry out. The air in the low-pressure belts is rising, which causes it to cool and moisten.

Wind belts are areas of the Earth’s atmosphere where the wind blows in a consistent direction. The trade winds blow from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. The westerlies blow from the west in the mid-latitudes. The polar easterlies blow from the east in the polar regions.

Jet streams are fast-flowing bands of air in the upper atmosphere. The jet streams are located at the boundaries between the high- and low-pressure belts. They play an important role in shaping the Earth’s weather patterns.

Monsoons are Seasonal Winds that blow in opposite directions between the land and the ocean. In the summer, the monsoons blow from the ocean to the land, bringing moisture and rain. In the winter, the monsoons blow from the land to the ocean, bringing dry air.

Horse latitudes are areas of the Earth’s atmosphere where the trade winds converge. The horse latitudes are located at about 30 degrees north and south latitude. The air in the horse latitudes is sinking, which causes it to warm and dry out. This can lead to the formation of deserts.

The Intertropical Convergence Zone (ITCZ) is a band of low pressure that circles the Earth near the equator. The ITCZ is where the trade winds from the Northern and Southern Hemispheres converge. The ITCZ is often associated with thunderstorms and rain.

Hadley cells are large circulation cells in the Earth’s atmosphere. The Hadley cells are driven by the Sun’s energy and the Earth’s rotation. The Hadley cells transport heat and moisture from the equator to the poles.

Ferrel cells are smaller circulation cells in the Earth’s atmosphere. The Ferrel cells are located in the mid-latitudes. The Ferrel cells are driven by the Earth’s rotation and the difference in temperature between the equator and the poles.

Polar cells are small circulation cells in the Earth’s atmosphere. The polar cells are located at the poles. The polar cells are driven by the Earth’s rotation and the difference in temperature between the equator and the poles.

The Earth’s rotation causes the Coriolis effect, which is a force that deflects moving objects to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. The Coriolis effect is responsible for the Earth’s wind belts and jet streams.

The Ekman spiral is a pattern of ocean currents that is caused by the Coriolis effect. The Ekman spiral is strongest near the surface of the ocean and weakens with depth.

Rossby waves are large, slow-moving waves in the Earth’s atmosphere. Rossby waves are caused by the Earth’s rotation and the difference in temperature between the equator and the poles. Rossby waves play an important role in shaping the Earth’s weather patterns.

Atmospheric circulation is the movement of air in the Earth’s atmosphere. Atmospheric circulation is driven by the Sun’s energy and the Earth’s rotation. The Sun’s energy heats the Earth’s surface, which causes the air to rise. The rising air creates an area of low pressure at the surface. The air from the surrounding areas flows into the low-pressure area, creating a wind. The Earth’s rotation causes the wind to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This deflection is called the Coriolis effect. The Coriolis effect causes the wind to blow in a circular pattern around the low-pressure area. This pattern is called a cyclone. Cyclones are often associated with thunderstorms and rain.

The Earth’s atmosphere is a complex system that is constantly in motion. The Sun’s energy and the Earth’s rotation drive the movement of air in the atmosphere. This movement of air creates pressure belts, wind belts, jet streams, and other features that shape our weather.

What is wind?

Wind is the movement of air from areas of high pressure to areas of low pressure.

What causes wind?

Wind is caused by the uneven heating of the Earth’s surface by the sun. The sun heats the Earth’s surface more at the equator than at the poles. This difference in temperature creates a difference in air pressure. The air at the equator is warmer and less dense than the air at the poles, so it rises. As the air rises, it creates an area of low pressure at the surface. The air at the poles is cooler and denser than the air at the equator, so it sinks. As the air sinks, it creates an area of high pressure at the surface. The air from the high pressure areas flows towards the low pressure areas, creating wind.

What are the different types of wind?

There are two main types of wind: prevailing winds and Local Winds. Prevailing winds are winds that blow in a consistent direction over a long period of time. Local winds are winds that blow in a particular area and are caused by local conditions, such as temperature differences or the shape of the land.

What are the effects of wind?

Wind has many effects on the Earth. It can cause erosion, transport water, and create waves. Wind can also be used to generate electricity.

What are some of the benefits of wind?

Wind is a renewable resource that does not produce greenhouse gases. Wind power can help to reduce our reliance on fossil fuels.

What are some of the challenges of wind?

Wind power is intermittent, meaning that it does not always blow when we need it. Wind turbines can also be noisy and can kill birds.

What is the future of wind power?

The future of wind power is promising. The cost of wind turbines has decreased significantly in recent years, and wind power is becoming more competitive with other forms of energy. Wind power is expected to play a significant role in the future of energy production.

Sure, here are some MCQs without mentioning the topic Pressure And Wind Belt1:

  1. What is the force that causes air to move?
    (A) Gravity
    (B) Pressure
    (C) Temperature
    (D) Wind

  2. What are the three main types of pressure systems?
    (A) High pressure, low pressure, and neutral pressure
    (B) Tropical, polar, and mid-latitude pressure systems
    (C) Continental, maritime, and equatorial pressure systems
    (D) Easterly, westerly, and northerly pressure systems

  3. What is the difference between a high pressure system and a low pressure system?
    (A) A high pressure system has high pressure at the center, while a low pressure system has low pressure at the center.
    (B) A high pressure system has sinking air, while a low pressure system has rising air.
    (C) A high pressure system has clear skies, while a low pressure system has cloudy skies.
    (D) All of the above

  4. What are the four main wind belts?
    (A) The trade winds, the prevailing westerlies, the polar easterlies, and the jet streams
    (B) The tropical easterlies, the subtropical westerlies, the polar easterlies, and the polar front jet streams
    (C) The equatorial easterlies, the trade winds, the westerlies, and the polar easterlies
    (D) The polar easterlies, the subpolar lows, the subtropical highs, and the equatorial lows

  5. What is the Coriolis effect?
    (A) The apparent deflection of objects moving in a straight line due to the Earth’s rotation
    (B) The force that causes air to move from high pressure to low pressure
    (C) The force that causes air to rise at the equator and sink at the poles
    (D) The force that causes the Earth’s atmosphere to circulate

  6. What is the jet stream?
    (A) A band of strong winds that flows around the Earth at high altitudes
    (B) A band of clouds that forms at the boundary between the tropical and polar air masses
    (C) A band of thunderstorms that forms at the boundary between the cold and warm air masses
    (D) A band of rain that forms at the boundary between the dry and wet air masses

  7. What are the three main Types Of Clouds?
    (A) Cirrus, cumulus, and stratus
    (B) Cumulonimbus, stratus, and nimbostratus
    (C) Cirrus, altocumulus, and stratocumulus
    (D) Cirrus, cumulus, and nimbus

  8. What is the difference between a cumulus cloud and a stratus cloud?
    (A) A cumulus cloud is a puffy cloud, while a stratus cloud is a flat cloud.
    (B) A cumulus cloud is made of water droplets, while a stratus cloud is made of ice crystals.
    (C) A cumulus cloud forms at low altitudes, while a stratus cloud forms at high altitudes.
    (D) All of the above

  9. What is the difference between a cumulonimbus cloud and a nimbostratus cloud?
    (A) A cumulonimbus cloud is a thunderstorm cloud, while a nimbostratus cloud is a rain cloud.
    (B) A cumulonimbus cloud is tall and puffy, while a nimbostratus cloud is low and flat.
    (C) A cumulonimbus cloud forms at low altitudes, while a nimbostratus cloud forms at high altitudes.
    (D) All of the above

  10. What is the difference between a cyclone and a hurricane?
    (A) A cyclone is a Tropical Cyclone that forms in the Northern Hemisphere, while a hurricane is a tropical cyclone that forms in the Southern Hemisphere.
    (B) A cyclone is a tropical cyclone that has wind speeds of less than 74 miles per hour, while a hurricane is a tropical cyclone that has wind speeds of 74 miles per hour or more.
    (C) A cyclone is a tropical cyclone that forms over warm waters, while a hurricane is a tropical cyclone that forms over cold waters.
    (D) All of the above

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