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Here is an essay an ‘Winds’ for class 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Winds’ especially written for school and college students.
Essay on Winds
Essay # 1. Planetary Winds:
These winds move in one direction throughout the year. They move from high pressure areas of major pressure belts to low pressure areas. These winds are also known as stable winds. Eastern or Equatorial winds, Trade winds, Western winds and Polar winds are examples of these winds.
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(a) Eastern or Equatorial Winds:
Region between 5°N latitude to 5°S latitude is known as Equatorial low pressure belt. This belt receives vertical rays of sun because of which temperature is very high and moreover the temperature of air present near the surface of Earth increases and air starts moving upward. These are known as equatorial winds or Doldrums.
In this belt mostly the winds move vertically and daily in the afternoon they bring heavy thunder showers, this region is also known as Inter-tropical convergence zone (IICZ) because trade winds of both hemispheres join here.
(b) Trade Winds:
Region of trade winds extends from Equatorial low pressure belt to 30° North and South latitude. In this region winds move from sub-tropical high pressure areas to low pressure areas of equatorial low pressure belt.
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Earth rotates an its axis from west to east and in northern hemisphere these winds deflect towards right under the coriolis effect and according to the rule/law of Farrel because of which these are known as North-Eastern trade winds. On the other hand in southern hemisphere these winds deflect towards left therefore these are known as south western trade winds.
According to the myth the name ‘Trade’ winds has been derived from the word ‘Track’ of German language which means a definite/particular path. Trade winds blow continuously in one direction with a definite speed. In ancient times sailors sail from one place to another with the help of these winds. These winds cross the oceans and bring rainfall in the eastern parts of continents while reaching upto western parts these become dry because of which mostly the deserts are found on the western parts.
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(c) Sub-Tropical Equatorial Winds:
The region is situated between 30° to 35°latitudes in both the hemispheres. This region matches to the vertical wind direction of equatorial region winds while in direction being exactly opposite to it. Hot air rises up in the equatorial regions but in this region air begins to descend toward the surface which results in cool and dry weather.
This region is also known as ‘Horse latitudes’ because according to a myth, in ancient times when sailors were dependent on winds for the movement of ships, they face problem in movement due to the reduction of speed of wind in this region. They used to drop their horses in the sea so that the weight of ship could be reduced and they could save it from sinking.
(d) Westerly’s:
Westerly’s are the prevailing winds in the middle latitudes (i.e. between 35 and 65 degree) in both hemispheres like Trade winds; these winds also change their direction due to Coriollis Effect. In northern hemisphere these blow from south west and in southern hemisphere these blow from North West. These winds bring rainfall in the western parts of continents.
Variations are found in speed and direction of these winds due to the irregular division of water and land in northern hemisphere. On the other hand most of southern hemisphere is covered by water in these latitudes because of which these winds are more strong and regular in this sphere. These winds also have some local names given by sailors like. Roaring Forties for 40° latitude, “Furious Fifties” (50 to 60 degrees south) and Shirking sixties for 60° latitude.
(e) Polar Winds:
Polar winds blow from high pressure polar regions to low pressure sub polar regions. Polar regions have low temperature and these are covered by ice. These winds are dry and do not bring rainfall because these are cold and do not attain moisture.
Polar regions are extremely cold and no one is living there because of which we do not have much information about these regions. But still we can say that as westerly’s these winds are more regular in southern hemisphere as compare to northern hemisphere.
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Shifting of Wind Belts:
Circulation of wind on the earth’s relief is quite different from the above mentioned conditions. We all know that earth rotates on its axis and it also revolves around sun and moreover it is inclined at 23 1/2°. Because of this the position of sun on Earth changes continuously in a year. Sun rays fall vertically on Equator as well as on Tropic of Cancer and Tropic of Capricorn.
Commonly we say that sun rays fall vertically on equator but if we study world air pressure maps for the month of January and July, we will come to know that air pressure belts change their position during these months.
On June 21 sun rays fall vertically on Tropic of Cancer. During these days Northern hemisphere has summer season and Southern hemisphere has winter season. Equatorial high temperature and low pressure regions shift towards north. Similarly other air pressure regions in northern hemisphere shit toward north and regions in southern hemisphere shift towards Equator.
Average situations are found twice in a year when sun rays fall directly on the Equator i.e. March 21 and September 23. This region has high temperature and low air pressure. Air pressure belts also shift on December 22 but their direction is opposite to the direction of June 21.
Due to the change in the situation of Sun and Earth, air pressure and wind belts shift from their definite position because of which various effect have been observed in white world.
Some of which are as follows:
i. Region which extends from 5° to 10° latitude on the both sides of equator remains hot and humid due to low air pressure in summer and in winters it remains dry by the effect of trade winds.
ii. The western parts of the continents which lie between 30° to 45° latitudes in both the hemispheres remain dry in summers due to effect of north eastern and south eastern Trade winds. When air pressure belts shift towards Equator in Northern hemisphere, Westerly’s bring rainfall in the western parts of the continents.
iii. Change in positioning of sun brings some difference in weather and seasons particularly in the regions falling between 60° and 70° latitudes in both the hemispheres. In Northern hemisphere where these higher latitudes find effect of Westerly’s, snow melts and vegetation starts growing. Similarly, cold effect in winter brings dry weather with Polar winds.
Generally Western winds bring rain while Polar winds bring dry spell with them.
iv. Regions of monsoon winds have been created in India and world due to the shifting of air pressure belts and wind belts. Moreover due to this effect these winds blow completely opposite to each other in summer and winter.
Essay # 2. Seasonal or Temporary Winds:
Seasonal winds are effected by the change in temperature and air pressure according to the change in season Monsoon winds are the finest example of these winds.
Origin of Indian Monsoon:
The Term ‘Monsoon’ has been derived from the Arabic word ‘mausim’ – meaning ‘Season’. Monsoon is a wind system in which there is complete reversal of prevailing direction of winds after every six months, i.e. from summer to winter and Vice Versa.
Concepts about the Origin of Monsoon:
Monsoon is a complex meteorological phenomenon.
Some of the important concepts about the origin of monsoon have been discussed as under:
The Thermal Concept or Classical theory was propounded of Halley in 1686. According to this concept, Monsoons are the extended land breeze and sea breeze on a large sale, produced by the differential heating of continents and ocean bodies. During the summers in northern hemisphere, When the sun rays are vertical over tropic of cancer, the huge landmass of Asia heats quickly and develops a strong low pressure centre near lake Baikal (Siberia) and Peshwara (Pakistan).
Moreover the pole ward shift of the Inter tropical Convergence Zone (ITCZ) to a position over Southern Asia reinforces the thermally induced low pressure centre in comparison to this, the pressure over the oceans towards the Indian and Pacific oceans is relatively high. Under these conditions, a sea to land pressure gradient develops.
Consequently, the surface air flow is from the high pressure over the ocean towards the low pressure areas over the heated land. Contrary to this during the winter season in the northern hemisphere these develops a high pressure over near Baikal (Siberia) and Peshwar and Indian and Pacific oceans are comparatively warm having a low pressure. The winds blow from Land to Sea.
Dynamic Concept:
The Dynamic Concept about the origin of Monsoon was put forward by Flohn in 1951. In his opinion, The Monsoon is the result of Seasonal Migration of Planetary Winds and pressure belts (fig.) The Inter-Tropical Convergence Zone At the time of Summer Solstice (21 June), when the sun rays are vertical over the tropic of cancer the North ITCZ is extended upto 30°N latitude, covering South and South-East Asia and thus equatorial westerly’s are established over these Areas. The equatorial westerly’s are established over these areas (fig.) The equatorial westerly’s become South-West or Summer Monsoon. The NITCZ is associated with numerous atmospheric streams (Cyclones).
Recent Concepts:
Tibetan Plateau and the circum Polar whirl. In 1973, the Monsoon Expedition (Monex) was organized under the Joint Venture of the former Soviet Moon and India. On the basis of investigation the meteorologists arrived at the conclusion that the Tibet Plateau plays a vital role in initiating the monsoon circulation over the Indian Subcontinent.
Tibet Plateau is a high table land with dimensions 2000 x (600 – 1000) square Kilometer it has an average height of 4 Kilometer.
Tibet Plateau affects the atmosphere in two ways:
(i) As a physical barrier, and
(ii) As a high level heat source.
At the beginning of June the Sub tropical Jet Stream disappears completely over northern India. (fig.).
At this time the Jet Stream shifts to the north of Himalayas and Tibet and takes up a position at about 40°N. The plateau of Tibet accentuates the northward displacement of Jet Stream. Thus the abrupt onset of Summer Monsoon at the beginning of June is prompted by the hydro-dynamic effect of the Himalayas and not by the thermally induced low pressure centre over north West India in the middle of October the Plateau Proves to be the most important factor in causing the advance of the Jet Stream South of Himalayas or bifurcate it into two parts.
EL Nino and Monsoon:
EL Nino meaning ‘Child Christ’ is a warm ocean current appearing along the Peru (South America) coast generally in December. It replaces the cold Peru or Humboldt current flowing along the Perm coast in normal years. Under Normal conditions, the Peru is Cold Water Current, while over the Western Pacific (Indonesia and Eastern Australia) the ocean current is warm and deep. (Fig.). The appearance of EL-Nino ‘reversal’ the condition’ these develops warm conditions over the eastern Pacific (Peru Coast) and Cold conditions in Western Pacific.
Whenever this usually warm ocean current (EL-Nino) is produced near the Peruvian Coast in South America, the amount of Precipitation in the coastal regions is usually high while the Australian and Indonesian coasts record drought conditions in brief, the occurrence of EL-Nino results into weak Monsoon causing droughts floods and failure of crops.
The Indian Ocean has been warming at a rate faster than ever before (1.2°C during the Past Century). It is also the largest consistent contributor to the global ocean warming trends. The Western Indian Ocean, traditionally thought to have cooler sea surface temperatures than the central and eastern Indian Ocean, is surprisingly showing an even stronger summer warming trend over the whole of the 20th Century then the central and eastern Indian Ocean.
El-Nino is abnormal warming of sea surface of south east Pacific Ocean during El-Nino event, Plankton does not flourish luxuriantly. Krill fish disappears. Penguins in Antarctica climate observe baby depression. Wild purple flower are found everywhere on Atacama sands. Thermocline either goes deeper or changes its ends. Tropical diseases increase manyfold. Landslides interrupt the system of life over piedmont plains of Andes or the western coast of South America.
South east Pacific ocean always remain a zone of confrontation between counter equatorial current and Humboldt cold ocean current, they tend to overpower each other. The constant upwelling of the cold water of Humboldt current generates cold sea surface and high air pressure. If west wind drift does not push sufficient cold water to it, counter equatorial current establishes its warm water over the larger areas and raises sea surface temperature and induces El Nino conditions.
A recent study focused on the causes of its warming and found that it was mainly due to EL-Nino events. Which are getting longer and more frequent during recent decades, possibly due to changing climate. These EL Nino events taken the summer westerly winds over the Indian Ocean. Winds have the effect of cooling the sea surface. Strong winds cause evaporation and loss of latent heat from the ocean leading to cooling. When the winds are weakened the opposite happens – The ocean warms.
The study published recently in the ‘Journal of Climate’ was undertaken by Dr. Roxy Mathew Koll of the Indian institute of Tropical Meteorology, Pune and has found that the ocean atmospheric Phenomenon-The EL-Nino, and the influence on the walker circulation were responsible for periodic weakening of Monsoon Westerly’s and led to abnormally high summer sea surface temperature in Western Indian Ocean.
The study has found that ‘The Frequency and magnitude of El-Ninos have also increased in the recent decades. Possibly due to global warming. This means a piling up of heat on the Indian Ocean. Mostly this effect has been observed in Asian countries like India, Malaysia, China, Korea, Japan and Taiwan. Moreover, we can also see this effect in USA, Northern Australia and Western Africa.
These winds originate due to the difference between the temperature of land and water regions. Moreover, shifting of air pressure belts due to change in the position of sun and Earth also act as a major reason for the origin of these winds.
Research about these winds is going on at world level with advanced scientific techniques so that we can understand the nature of these winds accurately. Study about the higher atmospheric activities is also going on, specially about the role of Jet stream.
La Nina:
The sea surface temperature of south east pacific ocean subsides by 3° to 5° Celsius. it leads to stronger Walker circulation. Robust, south east trade winds carry more moisture and all the places will be wetter than normal conditions on the eastern margins of the continents. Western margins will exhibit excessive drought conditions. Pre advent of Monsoon, excessive rainfall over south east and Eastern Africa are frequently associated with La-Nina.
It occurs when counter equatorial current is weak and west wind drift pushes more water in Humboldt current protracted La Nina conditions takes place on occasions. Mid 1998 to early 2001, the sea surface temperature of south east Pacific ocean remains excessively below normal. Last L Nina occurs in 2010-11 it is expected, 2017 is having an extra ordinary La-Nina year.
Essay # 3. Local Winds:
Local winds originate due to the difference between local relief and temperature and their effect is also local. These winds are limited upto particular region and local people give name of these winds. Name of these winds describe the affect on that particular region.
These winds can be further classified into two parts:
(i) Hot winds
(ii) Cold winds
(i) Hot Winds:
Hot winds originate by advection of hot air from warm source region and its movement toward adjacent region and moreover temperature of wind rises when it descends in mountainous region.
a. Foehn:
Fohn or Foehn is a type of dry, warm, down slope wind that occurs in the northern slopes of Alps mountain for its heal and dryness is its dry adiabatic rate which increases temperature even upto 10°C per kilometer while descending from mountain tops. In spring season these winds increase the temperature because of which the ice melts and conducive environment is created for the cultivation of wheat and growth of fodder for animals. Increase is temperature and decrease in humidity brings soothing effect in weather.
b. Chinook:
These are the hot and dry winds which descend toward Prairie plains from Rocky mountains of North America, particularly in Colorado, Wyoming, British Colombia and Montana states in spring season locally known as ‘Chinook’. ‘Chinook’ means ‘snow eater’ for locals. Like Foehn winds these are also very helpful for local people. These winds create conducive environment for the cultivation of crops, fodder for animals and also give relief from cold. Canadian Punjabis have given them a new name, ‘Shoonkan’.
c. Santa Ana:
These are hot and dry down slope winds like Foehn and Chinook, they blow in southern parts of California (USA) from Santa Ana mountainous regions to coastal plains. But these are harmful for orchards and other vegetation’s in plains and trees start dying because of dryness.
d. Loo:
These are hot and dry winds which blow in parts of northern India i.e. Punjab, Haryana, UP and Bihar during the month of May and June. These are very harmful for human beings and every year large number of people die because of these winds.
e. Khamsin:
These are hot and dry winds which blow in Egypt (Africa) from April to June and they carry dust particles with them. At times the blow off big dwellings.
f. Sirocco:
Hot, dry and dusty winds which blow towards north from Sahara desert are known as ‘Sirocco’ winds. These winds cross the Mediterranean sea and enter in Italy and Spain. These winds attain moisture while crossing the sea and bring rain laden with dust. This rainfall is harmful for crops.
g. Harmattan:
Harmattan winds are hot and dry and they blow from Sahara desert to Gulf of Guinea and carry dust particles with them. These winds decrease the humidity on the western coasts because of which local people have given the name ‘doctors’ to these winds.
(ii) Cold Winds:
a. Mistral:
Cold and dry winds blowing in Spain and France during winter season are known as Mistral winds. These winds blow from Mediterranean plateaus to valleys of Rhone. These winds decrease the temperature abruptly which affects the crops and human life.
b. Berg:
Cold and dry winds descending from the southern slopes of Alps mountain range are known as ‘Berg’. These winds affect the eastern coasts of ‘Adriatic Sea'(Italy).
c. Blizzard:
Cold and dry snowy winds blowing in snow/ice covered Polar Regions are known as Blizzard. As dust storms these winds also decrease the visibility. These winds blow in USA, Canada, Siberia and Antarctica.