Atmosphere: Structure, air pressure and air flow
2. 2. What are the main layers of the atmosphere according to the chemical composition of gases? Also briefly describe the characteristics of these layers.
Answer: Gases in the atmosphere are divided into two main categories according to their chemical composition:
(1) Homo sphere and (2) The heterosphere.
This lower layer is called the homosphere because the chemical composition of the gases in the atmosphere is often the same up to an altitude of about 80 km above the surface. Due to differences in some of the characteristics according to altitude, the homosphere layer is again divided from the surface into the troposphere, statosphere and mesosphere, respectively.
On the other hand, this layer is called the heterosphere because the gases in the atmosphere undergo special chemical changes beyond the mesosphere layer, ie above an altitude of 80 km. In this layer of the atmosphere, nitrogen, oxygen, helium and hydrogen gases form four layers according to their molecular masses. These layers are the nitrogen layer (80 km to 200 km), the oxygen layer (1125 km), the helium layer (3540 km) and the hydrogen layer (about 10,000 km). The density of air in this layer of the atmosphere is negligible.
3. The How many other layers can the atmosphere be divided into based on altitude and temperature fluctuations? Write with pictures and briefly describe the characteristics of each level.
Answer: The atmosphere can be divided into five layers based on altitude and temperature rise and fall and they are: troposphere, statosphere, mesosphere, thermosphere and exosphere.
the temperature of the atmosphere
1. Troposphere: The troposphere is the lowest layer of the atmosphere attached to the Earth's surface. The troposphere alone contains about three-fourths of the total gases in the atmosphere and almost all of the water vapor and dust. The temperature is higher at the bottom of this layer of the atmosphere and gradually decreases with increasing altitude. Almost all weather activities such as clouds, rain, cyclones, storms, etc. take place in this troposphere.
2) Stratosphere: The stratosphere is the layer just above the troposphere. The wind speed in this cloudless layer is almost horizontal and the sky paths are designed through this layer. This layer of the atmosphere contains a layer of ozone gas. Ozone gas molecules absorb ultraviolet rays from the sun that are harmful to life and cause air temperatures to rise in the stratosphere.
3) Mesosphere: The mesosphere is the upper limit of the stratosphere, the layer just above the stratosphere. The main characteristic of this layer is that the air temperature decreases with increasing altitude.
4. Thermosphere: The thermosphere is the upper boundary of the mesosphere, the layer just above the mesopause. In this layer, the air temperature rises to about 1650°C and the density of the air decreases to almost zero. It is noteworthy that this layer contains electrically charged ion particles. Radio waves sent from the Earth's surface are also reflected from this layer.
5) Exosphere: The topmost layer of the atmosphere above the thermosphere is called the exosphere. This layer extends from an altitude of 400 km to an altitude of 10,000 km. At such altitudes, the density of air molecules is very low. Air is very thin in this layer due to the predominance of hydrogen and helium gases only.
4. . Discuss the causes of atmospheric pressure variations with examples.
Answer: There are two main factors that cause atmospheric pressure to vary - air temperature and Earth's surface elevation.
1) Air temperature: The distribution of heat on the Earth's surface is not the same everywhere. This heat value mainly depends on the geographical location of the place, i.e. latitude. Such variations in heat distribution result in cold, temperate and hot regions of the Earth. Such temperature differences also cause pressure differences in the atmosphere adjacent to the Earth. Air expands as temperature increases and its density decreases as air expands. When the density decreases, the air becomes thinner. Such thin air pressure is also low. Warm air, on the other hand, has a higher water vapor retention capacity. When warm air becomes humid by extracting water vapor from the water body, the pressure of such humid air decreases. In contrast, cool air has a low water vapor capacity and dry air with low water vapor pressure is high. Higher temperatures reduce air pressure. This is why the air pressure increases from the equator to the bipolar regions.
2. Earth's surface elevation: The higher you go above sea level, the deeper the atmosphere, ie the amount of gas in the atmosphere, decreases. When the depth of the atmosphere decreases, it loses its mass and consequently the pressure of the air. This means that the atmospheric pressure decreases with increasing altitude and therefore the atmospheric pressure is lower at higher altitudes and relatively higher at lower altitudes. Air pressure decreases by 1 inch, or about 34 millibars, for every 900 feet of altitude. Therefore, the temperature varies due to the difference in altitude between the places. Such temperature differences also cause atmospheric pressure to fluctuate.
5. 5. Discuss the characteristics of the major pressure zones of the Earth with the help of diagrams.
Answer: The Earth's pressure zone Four main pressure zones have been identified on the Earth's surface according to the relative differences in atmospheric pressure:
a) Equatorial low pressure zone
b) Subtropical high pressure zone
c) Sub- polar low pressure zone
d) Polar high-pressure belt
a) Neutral Low Pressure Zone: This region has more water than land. Also, because of the higher temperatures, the air in this region contains more water vapor and therefore reduces the air pressure in this region. For this reason, the atmospheric pressure is locally low in the equatorial region. The air in this region is relatively warm, making it thinner and decreasing in density. In the equatorial low pressure region, the air heats up and rises.
b) Subtropical High Pressure Zone: Cold and heavy air also comes from the two polar regions. Near the northern Cancer and southern tropics, such heavy air and cold air combine to form high pressure circles. The wind speed in this area is predominantly downward and therefore wind or airflow is felt. The subtropical high pressure zone extends seasonally, sometimes slightly north and sometimes slightly south.
c) Sub-polar low pressure zone: The air in the sub-polar regions is dispersed towards the sub-tropical regions and then the air volume in the two sub-polar regions decreases and low pressure is created there. This pressure zone, however, moves sometimes slightly north and sometimes slightly south seasonally.
D. Polar High Pressure Zone: Both the poles of the Earth are covered with ice and extremely cold due to lack of direct sunlight. The air is very cool here. Due to extreme cold, water in this area freezes in the form of ice. The air in this region contains almost no water vapor. As a result, there is permanent high air pressure in the two polar regions.
6. . Write about the importance of the atmosphere in creating a favorable natural environment on Earth.
Answer: The atmosphere is a very important component of the Earth's natural environment. The soil and water, ie the lithosphere and hydrosphere, as well as the atmosphere, provide a favorable environment for the creation, development and habitation of life on Earth. This is called the biosphere. In addition to providing the gases needed by humans and plants in life, the atmosphere helps in the distribution and transport of heat and water vapor on the Earth's surface. The gases in the Earth's atmosphere are in the right proportions, so the surface temperature is conducive to humans and other living things. There is also some relief from the extreme cold and heat in many places due to the movement of the wind. This atmosphere prevents the ultraviolet rays from the sun, which are very deadly to life, from reaching the Earth. Weather and climate are created and changed within the atmosphere. The atmosphere is responsible for the rainfall on Earth and for the survival of plants and animals. In short, without the atmosphere, life on Earth is inconceivable.
7. What is airflow? Discuss the factors that cause airflow.
Answer: Air is never at steady state in the atmosphere. When air moves, it is called airflow. According to meteorology, when air moves parallel to the surface, it is called wind or air current.
The influence on the airflow of a place depends mainly on the difference in atmospheric temperature and the associated atmospheric pressure.
The main forces or factors in the generation of airflow are:
1) Compressive strength,
2) Gravity,
3) Centrifugal force,
4) Frictional strength
1. Pressure energy: The energy generated by the difference in atmospheric pressure at the surface of the earth mainly causes airflow. This is called compression force. In fact, the rate of difference in atmospheric pressure between two places is called pressure. The higher the pressure difference between the two places, the higher the airflow velocity. However, the longer the distance, the lower the speed. Again, since air always blows from a high pressure region to a low pressure region, the pressure between two places also determines the direction of air flow. Studying the pressure of an area gives information about the direction and speed of the wind prevailing there. High pressure in an area increases wind speed and creates an unstable atmospheric condition. When the pressure is very low, there is almost zero airflow and the atmosphere is calm.
2. Gravity: The earth's gravity does not seem to play a significant role directly in airflow. However, like the Sun, the Earth's gravity acts as a driving force in the airflow. In fact, the Earth's gravity holds the entire atmosphere around it. In addition, the weight or pressure of air depends mainly on the force of gravity. Since the gravitational force that attracts and holds air decreases with altitude, the air becomes thinner and the air pressure decreases as altitude increases. Thus, there is also a vertical flow of air from high to low pressure in the atmosphere. This is the difference in pressure due to the differences in the height of different landforms on the Earth's surface and this causes air to flow from the plains to the mountains. In addition, due to gravity, among other forces, the movement of air from one place to another is not completely straight but slightly curved.
3. Centrifugal force: Because the Earth rotates around its spine, an outward force arises from its center. This is called centrifugal force. This centrifugal force causes some deflection of the wind direction. This force is known as the Coriolis force because it was first discovered in 1844 by a French mathematician named Gaspard de Coriolis. The Coriolis force, along with the wind, has the same effect on all moving objects or phenomena on the surface. However, the value of the Coriolis force is not the same everywhere in the world. This force has a value of zero at the equator and gradually increases poleward, finally reaching a maximum at the poles. This means that the airflow anywhere on Earth except in the equatorial region is influenced by the Earth's rotation. Therefore, it can be said that the airflow we see actually originated in the context of the rotating Earth.
4. Friction force: The effect of friction force on airflow is very important. Friction acts negatively on wind speed. If the surface is full of mountains, plains, or trees, tall buildings, etc., the frictional force is high and the velocity is significantly reduced when air flows through such a surface. Therefore, when air flows slightly above the surface, the friction is significantly reduced and the wind speed increases. Similarly, when wind blows over a water surface or snow-covered area, its velocity is much less affected by friction.
8. What is the main cause of airflow? Briefly state the factors that determine its speed and direction.
Answer: The main cause of airflow is compressive force. This pressure first determines the direction and speed of the wind.
1. Pressure energy: The energy generated by the difference in atmospheric pressure at the surface of the earth mainly causes airflow. This is called compression force. In fact, the rate of difference in atmospheric pressure between two places is called pressure. The greater the pressure difference between the two places, the greater the airflow velocity. However, the longer the distance, the lower the speed. Again, since air always blows from a high pressure region to a low pressure region, the pressure between two places also determines the direction of airflow. Studying the pressure of an area gives information about the direction and speed of the wind prevailing there. High pressure in an area increases wind speed and creates an unstable atmospheric condition. When the pressure is very low, there is almost zero airflow and the atmospheric conditions are calm.
2. Gravity: The earth's gravity does not seem to play a significant role directly in airflow. However, like the Sun, the Earth's gravity acts as a driving force in the airflow. In fact, the entire atmosphere around the Earth is held by the Earth's gravity. In addition, the weight or pressure of air depends mainly on the force of gravity. Since the gravitational force that attracts and holds air decreases with altitude, the air becomes thinner and the air pressure decreases as altitude increases. Thus, there is also a vertical airflow from high pressure to low pressure in the atmosphere. This is the difference in pressure due to the differences in the height of different landforms on the Earth's surface and this causes air to flow from the plains to the mountains. In addition, due to gravity, among other forces, the movement of air from one place to another is not completely straight but slightly curved.
3. Centrifugal force: Because the Earth rotates around its spine, an outward force arises from its center. This is called centrifugal force. This centrifugal force causes some deflection of the wind direction. This force is known as the Coriolis force because it was first discovered in 1844 by a French mathematician named Gaspard de Coriolis. The Coriolis force, along with the wind, has the same effect on all moving objects or phenomena on the surface. However, the value of the Coriolis force is not the same everywhere in the world. This force has a value of zero at the equator and gradually increases poleward, finally reaching a maximum at the poles. This means that the airflow anywhere on Earth except in the equatorial region is affected by the Earth's rotation. Therefore, it can be said that the airflow we see actually originated in the context of the rotating Earth.
4. Friction force: The effect of friction force on airflow is very important. Friction acts negatively on wind speed. If the surface is filled with mud or trees, tall buildings, etc., the frictional force is high and the velocity is significantly reduced when air flows through such a surface. Therefore, when air flows slightly above the surface, the friction is significantly reduced and the wind speed increases. Similarly, when wind blows over a water surface or snow-covered area, its velocity is much less affected by friction.
9. What is the Coriolis Ball? Briefly describe its role in determining the direction of wind with diagrams.
Answer: Wind deflection under the influence of the Coriolis force Centrifugal force: Because the Earth rotates around its spine, an outward force arises from its center. This is called centrifugal force. This centrifugal force causes some deflection of the wind direction. This force is known as the Coriolis force because it was first discovered in 1844 by a French mathematician named Gaspard de Coriolis. The Coriolis force, along with the wind, has the same effect on all moving objects or phenomena on the Earth's surface. However, the value of the Coriolis force is not the same everywhere in the world. This force has a value of zero at the equator and gradually increases poleward, finally reaching a maximum at the poles. This means that the airflow anywhere on Earth except in the equatorial region is influenced by the Earth's rotation. Therefore, it can be said that the airflow we see actually originated in the context of the rotating Earth.
10. . What does 'pressure energy' mean? What is its role in airflow?
Answer: Air currents are primarily generated by forces arising due to differences in atmospheric pressure at the land surface. This is called compression force. In fact, the rate of difference in atmospheric pressure between two places is called pressure. The higher the pressure difference between the two places, the higher the airflow velocity. However, the longer the distance, the lower the speed. Again, since air always blows from a high pressure region to a low pressure region, the pressure between two places also determines the direction of air flow. Studying the pressure of an area gives information about the direction and speed of the wind prevailing there. High pressure in an area increases wind speed and creates an unstable atmospheric condition. When the pressure is very low, there is almost zero airflow and the atmosphere is calm.
11 . Briefly write about the role of Earth's gravity in airflow.
Answer: Earth's gravity does not seem to play a direct role in airflow. However, like the Sun, the Earth's gravity acts as a driving force in the airflow. In fact, the entire atmosphere around the Earth is held by its gravity. In addition, the weight or pressure of air depends mainly on the force of gravity. Since the gravitational force that attracts and holds air decreases with altitude, the air becomes thinner and the air pressure decreases as altitude increases. Thus, there is also a vertical flow of air in the atmosphere from high to low pressure. This is the difference in pressure due to the differences in the height of different landforms on the Earth's surface and this causes air to flow from the plains to the mountains. In addition, due to gravity, among other forces, the movement of air from one place to another is not completely straight but slightly curved.
12. What does it mean to name the wind? How is the air flowing over a place named?
Answer: The wind is named after the direction from which it blows. That is called wind naming. Winds are named according to the direction of flow.
The wind blowing from the west is called the west wind, and the wind blowing from the northeast is called the northeast wind. The air mass collects the physical properties of the area over which the wind blows, such as temperature and humidity. Therefore, the air flowing over the ocean contains a lot of water vapor. On the other hand, the air flowing over tropical deserts is dry and warm. The direction from which the wind comes from the surface is called windward and the direction from which it blows is called windward. This is how the air flowing over a place is named.
13. How is the wind speed determined? What are the units of its velocity?
Answer: Knowledge of wind speed and direction is very important in meteorological studies. However, the wind direction of a place can be determined by the movement of clouds, smoke, water waves, etc. However, a device called a wind vane can be used to determine the exact direction of the wind. Wind direction is usually expressed in degrees in terms of magnetic north. Wind speed is measured by an instrument called an anemometer. Nowadays, however, there are many types of anemometers. The anemograph automatically records the direction and speed of the wind. In 1805, the British scientist Sir Francis Beaufort developed a scale of 0-12 to measure the nature and effects of wind speed. This is called the Beaufort scale. The wind speed is expressed in knots. Wind speed is one knot, which means 1 nautical mile per hour. That is 1.854 km per hour or 30 km per minute. 9 meters.
14 . How are winds classified? Briefly discuss with examples.
Answer: Broadly or air currents or winds can be divided into three categories depending on their extent - - -
1. Main or primary ventilation
2. Secondary airflow
3. Local ventilation
1. Main or Primary Air Current: Primary or Primary Air Current is the air that usually circulates throughout the Earth depending on the distribution of the pressure zone permanently on the Earth's surface. Trade winds, westerly winds and polar winds belong to the primary air currents.
2. Secondary Winds: Secondary air currents are generally the air currents formed in different parts of the Earth due to differences in the nature of the landforms and the extent of land and water and regional and seasonal pressure and temperature differences. Cyclones, anticyclones, cyclones, air masses, wind fronts, monsoon winds, etc. are mainly secondary currents. Such air currents cause significant changes in the weather in a particular area and sometimes destabilize the atmosphere.
3. Local air currents: Local air currents or tertiary air currents are air currents that are formed over a limited area due to entirely local factors such as topography and higher variations. Its scope is very limited. These include water winds, land winds, mountain winds, etc.
15. 15 . What is primary airflow? Show the distribution of primary airflow in a figure. Mention its characteristics.
Answer: The primary or main air current is the air that usually circulates throughout the Earth depending on the distribution of pressure zones permanently on the Earth's surface.
Its main features are as follows -
1) The primary airflow creates the environment for other low-level airflows.
2. Such permanent air currents are constantly running from the subtropical and polar high pressure zones to the equatorial and subpolar low pressure zones in both hemispheres of the Earth.
Image:
16. What is a secondary wind? Describe its role in determining the climate of a place with examples.
Answer: Secondary winds are air currents formed in different parts of the Earth due to differences in the nature of the landforms and the extent of land water and regional and seasonal pressure and temperature differences. Cyclones, air masses, wind chills, monsoons, etc. are mainly secondary winds.
Secondary winds cause significant changes in the weather in a region and sometimes make the atmosphere unstable. External tropical cyclones cause frequent changes in the weather, mainly in temperate regions. Such cyclones cause dense clouds and heavy rains. When the air at high altitudes is too cold, thunderstorms with hail and lightning occur. But after a while the rain and clouds disappeared and the sky opened up. However, it feels a little cold as the wind is blowing. In summer, the subtropical cyclone enters the southern United States through the Gulf of Mexico, causing some rainfall in the region. Thus, rainfall occurs in many tropical coastal regions of the world. However, the eastward-moving air is warmed by the partially permanent countercyclones in the subtropics. Such air currents create an unusually warm dry weather. The central and southeastern United States experience almost such warm dry weather. In winter, the dry northeast monsoon winds absorb water vapor from the Bay of Bengal and then give some rainfall off the coast of Tamil Nadu in southern India.
17 . What is local wind? How local winds affect the weather of a place. Briefly discuss with examples.
Answer: Local wind is the air current that covers a limited area due to differences in topography and altitude.
Local warming in the tropics and subtropics causes low pressure centers. The strong attraction of such temporary low pressure centers causes some airflow. The chirocco is an extremely hot and dry southerly air current that originates in the Sahara Desert in North Africa. In Egypt such winds are called Khamsin and in Arabia Chimukh. This air is so high and dry that for several consecutive days, the skin of the human body begins to crack, the soil cracks and the trees begin to dry up and fall off. When such winds blow through the dry desert background, they carry large amounts of dust and sand and cause frequent dust storms. When such air currents created in the Thar Desert due to increased daytime temperatures in summer enter the Ganges plain region of northern India, they are called Lu. In winter, on the other hand, the mistral is a heavy cool breeze that blows from the highlands of southwestern Europe along the southern slopes to the Mediterranean coast. Thus, local winds bring about changes in the weather of an area at a local level.
18 . What is a 'cyclone'? What are the types and what are they? Briefly describe its effects on the weather or climate of a place.
Answer: A cyclone is a state of atmospheric flow in which strong winds move in a circular motion around a low pressure.
There are two main types of cyclones -
1) tropical cyclones,
2. Extratropical or intertropical cyclones.
These cyclones can occur at any time of the year. Such cyclones cause dense clouds and heavy rains. When the air at high altitudes is too cold, thunderstorms with hail and lightning occur. But after a while the rain and clouds disappeared and the sky opened up. The weather or climate in temperate regions changes frequently and appears unstable mainly due to external tropical cyclones.
19 . What is the 'air mass'? How is it classified ? What is its role in determining the climate of a place?
Answer: An air mass is a large mass of air with the same properties of heat, humidity, etc. They can be divided into four main categories depending on the air mass.
1. Continental air masses in the tropics.
2. Tropical ocean air masses.
3. Continental air masses in the polar regions.
4. Oceanic air masses in the polar regions.
The formation of a certain air mass determines the weather of the area over which it flows. Vertical heat distribution indicates the cooling and temperature of the air as well as the stability and instability of the atmosphere. When an air mass flows away from its source, the heat distribution varies, but its source can be identified by studying the horizontal heat and moisture distribution of the air mass. As air moves away from the highlands, it not only changes the weather but also changes its own temperature and humidity.
20 . What does 'Batagra' mean? How is it created? Briefly discuss the relationship between climate and wind speed.
Answer: When two masses of air with opposite properties of temperature, humidity, pressure, density etc. meet, a separating air surface or separating line is formed between the two without direct mixing. This is called Batagra.
The two air masses require special conditions to form a windstorm -
1. One of the two masses of air must be cooler and heavier than the other.
2. The airflow must be convergent so that the two air masses flow towards each other from opposite directions.
When two such masses of air with opposite properties meet, the relatively warm light air lands on top of the cool heavy air and remains in a stable state. In the windward region, the reversal of the pressure causes the air to dissipate and as the wind direction changes, clouds are formed in the windward region due to changes in the temperature and humidity of the associated air.
21 . What does it mean to be a 'monsoon' wind? How is it created? In which parts of the world is its impact most evident?
Answer: Monsoon winds are temporary air currents that flow seasonally, ie depending on the change of seasons. A monsoon is a type of surface air current whose direction of movement in summer is completely opposite to that in winter.
The direction of monsoon flow changes due to temperature and pressure variations depending on seasonal changes. Seasonal flows are most common in regions of the world that are surrounded by oceans (such as South Asia, Southeast Asia, Southeast China, etc.).
The monsoon effect is most pronounced and strongest in the southern and southeastern parts.
22 . Write the answer giving the reason:
(a) Why does weather activity occur mainly in the troposphere?
Answer: The troposphere alone contains about three-quarters of the total gases in the atmosphere and almost all of the water vapor and dust particles. The temperature at the bottom of this layer of the atmosphere is high and the temperature decreases gradually with increasing altitude. Almost all weather activities such as clouds, rain, cyclones, storms, etc. take place in this troposphere.
(b) What will be the consequences of an increase in the amount of carbon dioxide in the atmosphere?
Answer: An increase in the amount of carbon dioxide in the atmosphere will cause an increase in the temperature of the atmosphere.
(c) What is the pressure difference between moist air and dry air?
Answer: When warm air becomes moist by absorbing water vapor from the water body, the pressure of the moist air decreases. In contrast, cool air has a low water vapor holding capacity and dry air with low water vapor content has a high pressure. Therefore, the pressure of dry air is higher than that of moist air.
(d) How does the ozone layer benefit life?
Answer: Ozone gas at an altitude of about 40-50 km above the atmosphere absorbs ultraviolet rays which are very harmful to plants and animals and protects life from potential dangers.
(e) Why is the air pressure at sea level the highest?
Answer: The air pressure at sea level is highest because the sea floor is at low altitude, as the air pressure at low altitude is higher.
(f) Why is the vertical extent of the tropospheric layer different in the polar regions and the equatorial regions?
Answer: The vertical extent at the troposphere varies with latitude in the polar regions and equatorial regions.
(g) Why is wind blowing parallel to the surface not usually felt in the equatorial low pressure zone?
Answer: In the equatorial low pressure region, the air heats up and rises. In such circumstances, a wind blows parallel to the surface in this area.
23 . Answer the following questions briefly.
(a) How high does the atmosphere extend?
Answer: The atmosphere extends up to about 10,000 km from the Earth's surface.
(b) Up to what altitude above the Earth's surface do the chemical compositions of the gases in the atmosphere remain almost the same?
Answer: The chemical composition of the gases in the atmosphere is almost the same up to 80 km from the surface.
(c) What is the name of the boundary between the homosphere and the heterosphere?
Answer: The boundary between the homosphere and the heterosphere is called the mesopause.
(d) What is Ferrell’s formula ?
Answer: The Coriolis force caused by the Earth's rotation deflects the air currents in the Northern Hemisphere clockwise and the air currents in the Southern Hemisphere counterclockwise to the left. This is called Ferrell's formula.
( e ) What is the Beaufort Scale ? Briefly explain the usefulness of this scale with examples.
Answer: The scale of 0-12 developed by the British scientist Sir Francis Beaufort in 1805 measures the nature and effects of wind speed according to its value. This is called the Beaufort scale.
This scale is used to measure the nature and effects of wind speed. Wind speed is expressed in knots. Example - Beaufort Number 0; Wind speed as knots 1;nature of wind slow wind, effect of wind - smoke rises vertically.
( f ) Briefly define lapse rate.
Answer: The temperature is higher at the bottom of the troposphere and decreases gradually with increasing altitude. In general, the air temperature decreases by 6.5°C per km of altitude. This is called the lapse rate.
24 . Write a brief ?
a) Homosphere: This lower layer of the atmosphere is called the homosphere because the chemical composition of the gases in the atmosphere is often the same up to an altitude of about 80 km above the surface. Due to differences in some of the characteristics according to altitude, the homosphere layer is again divided from the surface into the troposphere, stratosphere and mesosphere, respectively.
b) Heterosphere: This layer is called the heterosphere because the gases in the atmosphere undergo special chemical changes from behind the mesosphere layer, i.e. from an altitude of 80 km upwards, creating a distinct state. In this layer of the atmosphere, nitrogen, oxygen, helium and hydrogen gases form four layers according to their molecular masses. The density of air in this layer of the atmosphere is negligible.
c) Relationship between air temperature, surface elevation and air pressure: Air is a gaseous substance. Because it has mass or weight, it also has pressure. Again, since the atmosphere is the aggregate of air; There is also atmospheric pressure. This atmospheric pressure is felt at the Earth's surface. The density of air varies due to its expanding and contracting properties. As the density of air increases, its pressure also increases. This means that the density and pressure of the atmosphere decreases from the surface.
d) Polar high pressure zone: In the absence of direct sunlight, both poles of the Earth are covered with ice and extremely cold. The air is very cool here. Due to extreme cold, water in this area freezes in the form of ice. The air in this region contains almost no water vapor. As a result, there is locally high air pressure in the two polar regions. Therefore, this region is called the polar high pressure zone.
e) Airflow system: Airflow is an essential medium of many activities in the atmosphere that constantly transport heat, moisture and many other physical properties of the atmosphere from one place to another. Hence, in a broad sense, it is called the ventilation system.
f) Pressure: Air currents are primarily generated by forces arising due to differences in atmospheric pressure at the land surface. This is called compression force. In fact, the rate of difference in atmospheric pressure between two places is called pressure. The greater the pressure difference between the two places, the greater the airflow velocity. However, the longer the distance, the lower the speed. Again, since air always blows from a high pressure region to a low pressure region, the pressure between two places also determines the direction of air flow. Studying the pressure of an area gives information about the direction and speed of the wind prevailing there. High pressure in an area increases wind speed and creates an unstable atmospheric condition. When the pressure is very low, there is almost zero airflow and the atmosphere is calm.
g) Trade: Trade winds are surface winds that flow from the subtropical high pressure zone around 30°N and 30°S latitude toward the equatorial low pressure zone. Due to the Coriolis force, the wind blows from northeast to southwest in the Northern Hemisphere and from southeast to northwest in the Southern Hemisphere. Therefore, it is called the Northeast Trade Wind in the Northern Hemisphere and the Southeast Trade Wind in the Southern Hemisphere.
H) Horse-latitude: There is also a calm zone of slow airflow in the part of the subtropical high pressure zone from which trade winds and westerly winds blow. The wind is outward from this region but in the middle of it the wind is almost motionless and calm. This region of the Earth's hemisphere, especially between 30° and 35° latitude, is called the horse latitude.
i) Roaring forty: The southern hemisphere, especially the region of 40° to 60° latitude, is covered by the ocean and therefore the intensity of the reverse winds is high in this part. Therefore, ocean mariners call the area of latitude in the forties the roaring forties.
j) Anti-cyclone: A countercyclone is when a high pressure circle is formed over a large area and a circular diverging air current is formed from its center. It is also called a high pressure center because the pressure is highest at the center of the countercyclone. In fact, a countercyclone is an atmospheric condition that is the exact opposite of a cyclone. Countercyclones occur in the subtropical and high latitude regions of both hemispheres. There are two main types of countercyclones -
1. Subtropical warm anticyclones and
2. High latitude cold anticyclone
k) Jet flow: A strong eastward wind blows through the upper layers of the tropics, similar to the westerly current. This is called the jet stream. Jet streams radically change the weather and climate of a place.
l) Equilateral line: When the pressure is very low, there is almost zero airflow and the atmospheric conditions are calm. When such conditions prevail over many areas, the isotope line (line connecting places with equal air pressure) is almost not visible on the isotope map of the area.
d) Tropical cyclones A tropical cyclone is a cyclone that occurs when strong winds from surrounding high pressure areas form a severe form around the low pressure in the tropics. Due to the rotation of the Earth, such cyclones rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. Tropical cyclones have speeds of 120 to 280 km per hour. Such cyclones are dangerous, destructive and harmful because a full-scale tropical cyclone releases very high amounts of energy. It is known as a cyclone on the eastern Pacific coast, a cyclone in the Indian Ocean region, and a rainbow in Assam.
25 Write the difference?
a) Horizontal flow and vertical flow
Answer: The motion of air is always horizontal.
When air rises, it is called a vertical flow.
The horizontal flow of air in the atmosphere is many times greater than the vertical flow.
b) Airflow and air mass:
Answer: When air moves, it is called wind or air current. This air flow is parallel to the surface. Airflow is an essential medium of many activities in the atmosphere that constantly transport heat, moisture and many other physical properties of the atmosphere from one place to another.
A mass of air is a large mass of air with the same properties of temperature and humidity.
c) Tropical cyclones and extratropical cyclones
Answer: A tropical cyclone is a cyclone when strong winds from the surrounding high pressure regions take a severe form around the low pressure in the tropics.
Cyclones that form in temperate and high latitude regions are called extratropical cyclones.
d) Hydrowind and land wind
Answer: Hydrowind is the flow from water to land during the day.
On the other hand, the current from land to water at night is called land wind.
e) Mountain winds and plain winds
Answer: The river flows up the mountain slopes from the valley or plain during the day The current is called the plain wind.
At night, the air in the highlands is cooler and heavier than in the plains. As a result, this air descends along the mountain slopes to the plains. This is called the wind in the mountains.
f) Cyclones and countercyclones
Answer: A cyclone is a state of atmospheric flow in which strong winds move in a circular motion around a low pressure. The wind speed is intensified because the surrounding atmospheric pressure is much higher than the low pressure at the center of the cyclone.
A countercyclone is when a high pressure circle forms over a large area and a circular diverging airflow from its center is formed.
Countercyclones play a negligible role in determining the weather of a place compared to cyclones.
g) Cold winds and warm winds
Answer: A wind front that displaces cold air is called a cold wind front.
On the other hand, a warm front is a front in which the leading warm air flows over the cold air and displaces it.
h) Troposphere and stratosphere: The troposphere is the lowest layer of the atmosphere attached to the Earth's surface. Almost all weather activities occur at this stage.
The stratosphere is the layer just above the troposphere. No weather activity, including cloud formation, is observed at this layer.
26. . Select the correct answer:
(a) Where is the ozone layer located?
(1) The troposphere
(2) The stratosphere.
(3) Mess ' sphere
(4) Thermosphere
Answer: 2) The stratosphere.
( b ) How much oxygen is in the atmosphere by volume ?
(1) 20. 98%
(2) 23. 01%
(3) 32. 07
(4) 78. 08%
Answer: 1) 20.94%
(c) The main cause of airflow is —
(1) Differences in appreciation
(2) Pressure variations
(3) Gravitational force
(4) Centrifugal force
Answer: 2) Pressure variation.
( d ) The wind speed measuring device is —
(1) Wind vane
(2) Anemometer
(3) Beaufort scale.
(4) Hydrometer.
Answer: 2) Anemometer.
( e ) The unit of wind speed is —
(1) Not
(2) millibars |
(3) Percentage.
(4) Degree
Answer: 1) Not.
(f) Monsoon winds belong to which of the following categories?
(1) Local wind.
(2) Primary Batah
(3) Secondary Batah
(4) Regular batah
Answer: 3) Secondary wind
(g) The name of the cyclone along the eastern Pacific coast is —
(1) Chaikl'n.
(2) Hurricanes
(3) Willy Willy
(4) Typhoon
Answer: 4) Typhoon.
Editing By:- Lipi Medhi
