General circulation of the atmosphere The pattern of the movement of the planetary winds is called the general circulation of the atmosphere. The general circulation of the atmosphere also sets in motion the ocean water circulation which influences the earth’s climate. Hadley Cell The air at the Inter Tropical Convergence Zone (ITCZ) rises because of the convection currents caused by low pressure. Low pressure in turn occurs due to high insolation. The winds from the tropics converge at this low pressure zone. The converged air rises along with the convective cell. It reaches the top of the troposphere up to an altitude of 14 km, and moves towards the poles. This causes accumulation of air at about 30° N and S. Part of the accumulated air sinks to the ground and forms a subtropical high. Another reason for sinking is the cooling of air when it reaches 30° N and S latitudes. Down below near the land surface the air flows towards the equator as the easterlies. The easterlies from either side of the equator converge in the Inter Tropical Convergence Zone (ITCZ). Such circulations from the surface upwards and vice-versa are called cells. Such a cell in the tropics is called Hadley Cell. Ferrel Cell In the middle latitudes the circulation is that of sinking cold air that comes from the poles and the rising warm air that blows from the subtropical high. At the surface these winds are called westerlies and the cell is known as the Ferrel cell. Polar Cell At polar latitudes the cold dense air subsides near the poles and blows towards middle latitudes as the polar easterlies. This cell is called the polar cell. These three cells set the pattern for the general circulation of the atmosphere. The transfer of heat energy from lower latitudes to higher latitudes maintains the general circulation. The general circulation of the atmosphere also affects the oceans. The large-scale winds of the atmosphere initiate large and slow moving currents of the ocean. Oceans in turn provide input of energy and water vapors into the air. These interactions take place rather slowly over a large part of the ocean. Walker Cell Warming and cooling of the Pacific Ocean is most important in terms of general atmospheric circulation. The warm water of the central Pacific Ocean slowly drifts towards South American coast and replaces the cool Peruvian current. Such appearance of warm water off the coast of Peru is known as the El Nino. The El Nino event is closely associated with the pressure changes in the Central Pacific and Australia. This change in pressure condition over Pacific is known as the southern oscillation. The combined phenomenon of southern oscillation and El Nino is known as ENSO. In the years when the ENSO is strong, large-scale variations in weather occur over the world. The arid west coast of South America receives heavy rainfall, drought occurs in Australia and sometimes in India and floods in China. This phenomenon is closely monitored and is used for long range forecasting in major parts of the world. (El-Nino in detail later) Classification of Winds Permanent winds or Primary winds or Prevailing winds or Planetary Winds The trade winds, westerlies and easterlies. Secondary or Periodic Winds Seasonal winds: These winds change their direction in different seasons. For example monsoons in India. Periodic winds: Land and sea breeze, mountain and valley breeze. Local winds These blow only during a particular period of the day or year in a small area. Winds like Loo, Mistral, Foehn, Bora. Primary Winds or Prevailing Winds or Permanent Winds or Planetary Winds These are the planetary winds which blow extensively over continents and oceans. The two most well- understood and significant winds for climate and human activities are trade winds and westerly winds. Trade Winds The trade winds are those blowing from the sub-tropical high pressure areas towards the equatorial low pressure belt. Therefore, these are confined to a region between 30°N and 30°S throughout the earth’s surface. They flow as the north-eastern trades in the northern hemisphere and the south-eastern trades in the southern hemisphere. This deflection in their ideally expected north-south direction is explained on the basis of Coriolis force and Farrells law. Trade winds are descending and stable in areas of their origin (sub-tropical high pressure belt), and as they reach the equator, they become humid and warmer after picking up moisture on their way. The trade winds from two hemispheres meet at the equator, and due to convergence they rise and cause heavy rainfall. The eastern parts of the trade winds associated with the cool ocean currents are drier and more stable than the western parts of the ocean. Westerlies The westerlies are the winds blowing from the sub-tropical high pressure belts towards the sub polar low pressure belts. They blow from south­west to north-east in the northern hemisphere and north-west to south-east in the southern hemisphere. The westerlies of the southern hemisphere are stronger and persistent due to the vast expanse of water, while those of the northern hemisphere are irregular because of uneven relief of vast land-masses. The westerlies are best developed between 40° and 65°S latitudes. These latitudes are often called Roaring Forties, Furious Fifties, and Shrieking Sixties – dreaded terms for sailors. The poleward boundary of the westerlies is highly fluctuating. There are many seasonal and short-term fluctuations. These winds produce wet spells and variability in weather. Polar easterlies The Polar easterlies are dry, cold prevailing winds blowing from north-east to south-west direction in Northern Hemisphere and south-east to north-west in Southern Hemisphere. They blow from the polar high-pressure areas of the sub-polar lows. Secondary Winds or Periodic Winds These winds change their direction with change in season. Monsoons are the best example of large-scale modification of the planetary wind system. Other examples of periodic winds include land and sea breeze, mountain and valley breeze, cyclones and anticyclones, and air masses. Monsoons Monsoons were traditionally explained as land and sea breezes on a large scale. Thus, they were considered a convectional circulation on a giant scale. The monsoons are characterized by seasonal reversal of wind direction. During summer, the trade winds of southern hemisphere are pulled northwards by an apparent northward movement of the sun and by an intense low pressure core in the north-west of the Indian sub­continent. While crossing the equator, these winds get deflected to their right under the effect of Coriolis force. These winds now approach the Asian landmass as south-west monsoons. Since they travel a long distance over a vast expanse of water, by the time they reach the south-western coast of India, they are over-saturated with moisture and cause heavy rainfall in India and neighboring countries. During winter, these conditions are reversed and a high pressure core is created to the north of the Indian subcontinent. Divergent winds are produced by this anticyclonic movement which travels southwards towards the equator. This movement is enhanced by the apparent southward movement of the sun. These are north-east or winter monsoons which are responsible for some precipitation along the east coast of India. The monsoon winds flow over India , Pakistan, Bangladesh, Myanmar (Burma), Sri Lanka, the Arabian Sea, Bay of Bengal, south­eastern Asia, northern Australia, China and Outside India, in the eastern Asiatic countries, such as China and Japan, the winter monsoon is stronger than the summer monsoon. (we will study about monsoons in detail while studying Indian Climate) Land Breeze and Sea Breeze The land and sea absorb and transfer heat differently. During the day the land heats up faster and becomes warmer than the sea. Therefore, over the land the air rises giving rise to a low pressure area, whereas the sea is relatively cool and the pressure over sea is relatively high. Thus, pressure gradient from sea to land is created and the wind blows from the sea to the land as the sea breeze. In the night the reversal of condition takes place. The land loses heat faster and is cooler than the sea. The pressure gradient is from the land to the sea and hence land breeze results. Valley Breeze and Mountain Breeze In mountainous regions, during the day the slopes get heated up and air moves upslope and to fill the resulting gap the air from the valley blows up the valley. This wind is known as the valley breeze. During the night the slopes get cooled and the dense air descends into the valley as the mountain wind. The cool air, of the high plateaus and ice fields draining into the valley is called katabatic wind. Another type of warm wind (katabatic wind) occurs on the leeward side of the mountain ranges. The moisture in these winds, while crossing the mountain ranges condense and precipitate. When it descends down the leeward side of the slope the dry air gets warmed up by adiabatic process. This dry air may melt the snow in a short time. Local Winds Local differences of temperature and pressure produce local winds. Such winds are local in extent and are confined to the lowest levels of the troposphere. Some examples of local winds are discussed below. Loo Harmful Wind In the plains of northern India and Pakistan, sometimes a very hot and dry wind blows from the west in the months of May and June, usually in the afternoons. It is known as Its temperature invariably ranges between 45°C and 50°C. It may cause sunstroke to people. Foehn or Fohn Beneficial Wind Foehn is a hot wind of local importance in the Alps. It is a strong, gusty, dry and warm wind which develops on the leeward side of a mountain range. As the windward side takes away whatever moisture there is in the incoming wind in the form of orographic precipitation, the air that descends on the leeward side is dry and warm (Katabatic Wind). The temperature of the wind varies between 15°C and 20°C. The wind helps animal grazing by melting snow and aids the ripening of grapes. Chinook Beneficial Wind Foehn like winds in USA and Canada move down the west slopes of the Rockies and are known as It is beneficial to ranchers east of the Rockies as it keeps the grasslands clear of snow during much of the winter. Mistral Harmful Wind Mistral is one of the local names given to such winds that blow from the Alps over France towards the Mediterranean Sea. It is channeled through the Rhine valley. It is very cold and dry with a high speed. It brings blizzards into southern France. Sirocco Harmful Wind Sirocco is a Mediterranean wind that comes from the Sahara and reaches hurricane speeds in North Africa and Southern Europe. It arises from a warm, dry, tropical air mass that is pulled northward by low-pressure cells moving eastward across the Mediterranean Sea, with the wind originating in the Arabian or Sahara deserts. The hotter, drier continental air mixes with the cooler, wetter air of the maritime cyclone, and the counter-clockwise circulation of the low propels the mixed air across the southern coasts of Europe. The Sirocco causes dusty dry conditions along the northern coast of Africa, storms in the Mediterranean Sea, and cool wet weather in Europe.

General circulation of the atmosphere The pattern of the movement of the planetary winds is called the general circulation of the atmosphere. The general circulation of the atmosphere also sets in motion the ocean water circulation which influences the earth’s climate. Hadley Cell The air at the Inter Tropical Convergence Zone (ITCZ) rises because of the convection currents caused by low pressure. Low pressure in turn occurs due to high insolation. The winds from the tropics converge at this low pressure zone. The converged air rises along with the convective cell. It reaches the top of the troposphere up to an altitude of 14 km, and moves towards the poles. This causes accumulation of air at about 30° N and S. Part of the accumulated air sinks to the ground and forms a subtropical high. Another reason for sinking is the cooling of air when it reaches 30° N and S latitudes. Down below near the land surface the air flows towards the equator as the easterlies. The easterlies from either side of the equator converge in the Inter Tropical Convergence Zone (ITCZ). Such circulations from the surface upwards and vice-versa are called cells. Such a cell in the tropics is called Hadley Cell. Ferrel Cell In the middle latitudes the circulation is that of sinking cold air that comes from the poles and the rising warm air that blows from the subtropical high. At the surface these winds are called westerlies and the cell is known as the Ferrel cell. Polar Cell At polar latitudes the cold dense air subsides near the poles and blows towards middle latitudes as the polar easterlies. This cell is called the polar cell. These three cells set the pattern for the general circulation of the atmosphere. The transfer of heat energy from lower latitudes to higher latitudes maintains the general circulation. The general circulation of the atmosphere also affects the oceans. The large-scale winds of the atmosphere initiate large and slow moving currents of the ocean. Oceans in turn provide input of energy and water vapors into the air. These interactions take place rather slowly over a large part of the ocean. Walker Cell Warming and cooling of the Pacific Ocean is most important in terms of general atmospheric circulation. The warm water of the central Pacific Ocean slowly drifts towards South American coast and replaces the cool Peruvian current. Such appearance of warm water off the coast of Peru is known as the El Nino. The El Nino event is closely associated with the pressure changes in the Central Pacific and Australia. This change in pressure condition over Pacific is known as the southern oscillation. The combined phenomenon of southern oscillation and El Nino is known as ENSO. In the years when the ENSO is strong, large-scale variations in weather occur over the world. The arid west coast of South America receives heavy rainfall, drought occurs in Australia and sometimes in India and floods in China. This phenomenon is closely monitored and is used for long range forecasting in major parts of the world. (El-Nino in detail later) Classification of Winds Permanent winds or Primary winds or Prevailing winds or Planetary Winds The trade winds, westerlies and easterlies. Secondary or Periodic Winds Seasonal winds: These winds change their direction in different seasons. For example monsoons in India. Periodic winds: Land and sea breeze, mountain and valley breeze. Local winds These blow only during a particular period of the day or year in a small area. Winds like Loo, Mistral, Foehn, Bora. Primary Winds or Prevailing Winds or Permanent Winds or Planetary Winds These are the planetary winds which blow extensively over continents and oceans. The two most well- understood and significant winds for climate and human activities are trade winds and westerly winds. Trade Winds The trade winds are those blowing from the sub-tropical high pressure areas towards the equatorial low pressure belt. Therefore, these are confined to a region between 30°N and 30°S throughout the earth’s surface. They flow as the north-eastern trades in the northern hemisphere and the south-eastern trades in the southern hemisphere. This deflection in their ideally expected north-south direction is explained on the basis of Coriolis force and Farrells law. Trade winds are descending and stable in areas of their origin (sub-tropical high pressure belt), and as they reach the equator, they become humid and warmer after picking up moisture on their way. The trade winds from two hemispheres meet at the equator, and due to convergence they rise and cause heavy rainfall. The eastern parts of the trade winds associated with the cool ocean currents are drier and more stable than the western parts of the ocean. Westerlies The westerlies are the winds blowing from the sub-tropical high pressure belts towards the sub polar low pressure belts. They blow from south­west to north-east in the northern hemisphere and north-west to south-east in the southern hemisphere. The westerlies of the southern hemisphere are stronger and persistent due to the vast expanse of water, while those of the northern hemisphere are irregular because of uneven relief of vast land-masses. The westerlies are best developed between 40° and 65°S latitudes. These latitudes are often called Roaring Forties, Furious Fifties, and Shrieking Sixties – dreaded terms for sailors. The poleward boundary of the westerlies is highly fluctuating. There are many seasonal and short-term fluctuations. These winds produce wet spells and variability in weather. Polar easterlies The Polar easterlies are dry, cold prevailing winds blowing from north-east to south-west direction in Northern Hemisphere and south-east to north-west in Southern Hemisphere. They blow from the polar high-pressure areas of the sub-polar lows. Secondary Winds or Periodic Winds These winds change their direction with change in season. Monsoons are the best example of large-scale modification of the planetary wind system. Other examples of periodic winds include land and sea breeze, mountain and valley breeze, cyclones and anticyclones, and air masses. Monsoons Monsoons were traditionally explained as land and sea breezes on a large scale. Thus, they were considered a convectional circulation on a giant scale. The monsoons are characterized by seasonal reversal of wind direction. During summer, the trade winds of southern hemisphere are pulled northwards by an apparent northward movement of the sun and by an intense low pressure core in the north-west of the Indian sub­continent. While crossing the equator, these winds get deflected to their right under the effect of Coriolis force. These winds now approach the Asian landmass as south-west monsoons. Since they travel a long distance over a vast expanse of water, by the time they reach the south-western coast of India, they are over-saturated with moisture and cause heavy rainfall in India and neighboring countries. During winter, these conditions are reversed and a high pressure core is created to the north of the Indian subcontinent. Divergent winds are produced by this anticyclonic movement which travels southwards towards the equator. This movement is enhanced by the apparent southward movement of the sun. These are north-east or winter monsoons which are responsible for some precipitation along the east coast of India. The monsoon winds flow over India , Pakistan, Bangladesh, Myanmar (Burma), Sri Lanka, the Arabian Sea, Bay of Bengal, south­eastern Asia, northern Australia, China and Outside India, in the eastern Asiatic countries, such as China and Japan, the winter monsoon is stronger than the summer monsoon. (we will study about monsoons in detail while studying Indian Climate) Land Breeze and Sea Breeze The land and sea absorb and transfer heat differently. During the day the land heats up faster and becomes warmer than the sea. Therefore, over the land the air rises giving rise to a low pressure area, whereas the sea is relatively cool and the pressure over sea is relatively high. Thus, pressure gradient from sea to land is created and the wind blows from the sea to the land as the sea breeze. In the night the reversal of condition takes place. The land loses heat faster and is cooler than the sea. The pressure gradient is from the land to the sea and hence land breeze results. Valley Breeze and Mountain Breeze In mountainous regions, during the day the slopes get heated up and air moves upslope and to fill the resulting gap the air from the valley blows up the valley. This wind is known as the valley breeze. During the night the slopes get cooled and the dense air descends into the valley as the mountain wind. The cool air, of the high plateaus and ice fields draining into the valley is called katabatic wind. Another type of warm wind (katabatic wind) occurs on the leeward side of the mountain ranges. The moisture in these winds, while crossing the mountain ranges condense and precipitate. When it descends down the leeward side of the slope the dry air gets warmed up by adiabatic process. This dry air may melt the snow in a short time. Local Winds Local differences of temperature and pressure produce local winds. Such winds are local in extent and are confined to the lowest levels of the troposphere. Some examples of local winds are discussed below. Loo Harmful Wind In the plains of northern India and Pakistan, sometimes a very hot and dry wind blows from the west in the months of May and June, usually in the afternoons. It is known as Its temperature invariably ranges between 45°C and 50°C. It may cause sunstroke to people. Foehn or Fohn Beneficial Wind Foehn is a hot wind of local importance in the Alps. It is a strong, gusty, dry and warm wind which develops on the leeward side of a mountain range. As the windward side takes away whatever moisture there is in the incoming wind in the form of orographic precipitation, the air that descends on the leeward side is dry and warm (Katabatic Wind). The temperature of the wind varies between 15°C and 20°C. The wind helps animal grazing by melting snow and aids the ripening of grapes. Chinook Beneficial Wind Foehn like winds in USA and Canada move down the west slopes of the Rockies and are known as It is beneficial to ranchers east of the Rockies as it keeps the grasslands clear of snow during much of the winter. Mistral Harmful Wind Mistral is one of the local names given to such winds that blow from the Alps over France towards the Mediterranean Sea. It is channeled through the Rhine valley. It is very cold and dry with a high speed. It brings blizzards into southern France. Sirocco Harmful Wind Sirocco is a Mediterranean wind that comes from the Sahara and reaches hurricane speeds in North Africa and Southern Europe. It arises from a warm, dry, tropical air mass that is pulled northward by low-pressure cells moving eastward across the Mediterranean Sea, with the wind originating in the Arabian or Sahara deserts. The hotter, drier continental air mixes with the cooler, wetter air of the maritime cyclone, and the counter-clockwise circulation of the low propels the mixed air across the southern coasts of Europe. The Sirocco causes dusty dry conditions along the northern coast of Africa, storms in the Mediterranean Sea, and cool wet weather in Europe.

Abhimanyusir.blogspot.com #AbhimanyuDahiya #UlimateGeography #Abhimanyusir Class 10 Social Science Class 12 Geography Previous Year Paper

Types of Winds: Permanent, Secondary & Local Winds

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General circulation of the atmosphere The pattern of the movement of the planetary winds is called the general circulation of the atmosphere. The general circulation of the atmosphere also sets in motion the ocean water circulation which influences the earth’s climate. Hadley Cell The air at the Inter Tropical Convergence Zone (ITCZ) rises because of the convection currents caused by low pressure. Low pressure in turn occurs due to high insolation. The winds from the tropics converge at this low pressure zone. The converged air rises along with the convective cell. It reaches the top of the troposphere up to an altitude of 14 km, and moves towards the poles. This causes accumulation of air at about 30° N and S. Part of the accumulated air sinks to the ground and forms a subtropical high. Another reason for sinking is the cooling of air when it reaches 30° N and S latitudes. Down below near the land surface the air flows towards the equator as the easterlies. The easterlies from either side of the equator converge in the Inter Tropical Convergence Zone (ITCZ). Such circulations from the surface upwards and vice-versa are called cells. Such a cell in the tropics is called Hadley Cell. Ferrel Cell In the middle latitudes the circulation is that of sinking cold air that comes from the poles and the rising warm air that blows from the subtropical high. At the surface these winds are called westerlies and the cell is known as the Ferrel cell. Polar Cell At polar latitudes the cold dense air subsides near the poles and blows towards middle latitudes as the polar easterlies. This cell is called the polar cell. These three cells set the pattern for the general circulation of the atmosphere. The transfer of heat energy from lower latitudes to higher latitudes maintains the general circulation. The general circulation of the atmosphere also affects the oceans. The large-scale winds of the atmosphere initiate large and slow moving currents of the ocean. Oceans in turn provide input of energy and water vapors into the air. These interactions take place rather slowly over a large part of the ocean. Walker Cell Warming and cooling of the Pacific Ocean is most important in terms of general atmospheric circulation. The warm water of the central Pacific Ocean slowly drifts towards South American coast and replaces the cool Peruvian current. Such appearance of warm water off the coast of Peru is known as the El Nino. The El Nino event is closely associated with the pressure changes in the Central Pacific and Australia. This change in pressure condition over Pacific is known as the southern oscillation. The combined phenomenon of southern oscillation and El Nino is known as ENSO. In the years when the ENSO is strong, large-scale variations in weather occur over the world. The arid west coast of South America receives heavy rainfall, drought occurs in Australia and sometimes in India and floods in China. This phenomenon is closely monitored and is used for long range forecasting in major parts of the world. (El-Nino in detail later) Classification of Winds Permanent winds or Primary winds or Prevailing winds or Planetary Winds The trade winds, westerlies and easterlies. Secondary or Periodic Winds Seasonal winds: These winds change their direction in different seasons. For example monsoons in India. Periodic winds: Land and sea breeze, mountain and valley breeze. Local winds These blow only during a particular period of the day or year in a small area. Winds like Loo, Mistral, Foehn, Bora. Primary Winds or Prevailing Winds or Permanent Winds or Planetary Winds These are the planetary winds which blow extensively over continents and oceans. The two most well- understood and significant winds for climate and human activities are trade winds and westerly winds. Trade Winds The trade winds are those blowing from the sub-tropical high pressure areas towards the equatorial low pressure belt. Therefore, these are confined to a region between 30°N and 30°S throughout the earth’s surface. They flow as the north-eastern trades in the northern hemisphere and the south-eastern trades in the southern hemisphere. This deflection in their ideally expected north-south direction is explained on the basis of Coriolis force and Farrells law. Trade winds are descending and stable in areas of their origin (sub-tropical high pressure belt), and as they reach the equator, they become humid and warmer after picking up moisture on their way. The trade winds from two hemispheres meet at the equator, and due to convergence they rise and cause heavy rainfall. The eastern parts of the trade winds associated with the cool ocean currents are drier and more stable than the western parts of the ocean. Westerlies The westerlies are the winds blowing from the sub-tropical high pressure belts towards the sub polar low pressure belts. They blow from south­west to north-east in the northern hemisphere and north-west to south-east in the southern hemisphere. The westerlies of the southern hemisphere are stronger and persistent due to the vast expanse of water, while those of the northern hemisphere are irregular because of uneven relief of vast land-masses. The westerlies are best developed between 40° and 65°S latitudes. These latitudes are often called Roaring Forties, Furious Fifties, and Shrieking Sixties – dreaded terms for sailors. The poleward boundary of the westerlies is highly fluctuating. There are many seasonal and short-term fluctuations. These winds produce wet spells and variability in weather. Polar easterlies The Polar easterlies are dry, cold prevailing winds blowing from north-east to south-west direction in Northern Hemisphere and south-east to north-west in Southern Hemisphere. They blow from the polar high-pressure areas of the sub-polar lows. Secondary Winds or Periodic Winds These winds change their direction with change in season. Monsoons are the best example of large-scale modification of the planetary wind system. Other examples of periodic winds include land and sea breeze, mountain and valley breeze, cyclones and anticyclones, and air masses. Monsoons Monsoons were traditionally explained as land and sea breezes on a large scale. Thus, they were considered a convectional circulation on a giant scale. The monsoons are characterized by seasonal reversal of wind direction. During summer, the trade winds of southern hemisphere are pulled northwards by an apparent northward movement of the sun and by an intense low pressure core in the north-west of the Indian sub­continent. While crossing the equator, these winds get deflected to their right under the effect of Coriolis force. These winds now approach the Asian landmass as south-west monsoons. Since they travel a long distance over a vast expanse of water, by the time they reach the south-western coast of India, they are over-saturated with moisture and cause heavy rainfall in India and neighboring countries. During winter, these conditions are reversed and a high pressure core is created to the north of the Indian subcontinent. Divergent winds are produced by this anticyclonic movement which travels southwards towards the equator. This movement is enhanced by the apparent southward movement of the sun. These are north-east or winter monsoons which are responsible for some precipitation along the east coast of India. The monsoon winds flow over India , Pakistan, Bangladesh, Myanmar (Burma), Sri Lanka, the Arabian Sea, Bay of Bengal, south­eastern Asia, northern Australia, China and Outside India, in the eastern Asiatic countries, such as China and Japan, the winter monsoon is stronger than the summer monsoon. (we will study about monsoons in detail while studying Indian Climate) Land Breeze and Sea Breeze The land and sea absorb and transfer heat differently. During the day the land heats up faster and becomes warmer than the sea. Therefore, over the land the air rises giving rise to a low pressure area, whereas the sea is relatively cool and the pressure over sea is relatively high. Thus, pressure gradient from sea to land is created and the wind blows from the sea to the land as the sea breeze. In the night the reversal of condition takes place. The land loses heat faster and is cooler than the sea. The pressure gradient is from the land to the sea and hence land breeze results. Valley Breeze and Mountain Breeze In mountainous regions, during the day the slopes get heated up and air moves upslope and to fill the resulting gap the air from the valley blows up the valley. This wind is known as the valley breeze. During the night the slopes get cooled and the dense air descends into the valley as the mountain wind. The cool air, of the high plateaus and ice fields draining into the valley is called katabatic wind. Another type of warm wind (katabatic wind) occurs on the leeward side of the mountain ranges. The moisture in these winds, while crossing the mountain ranges condense and precipitate. When it descends down the leeward side of the slope the dry air gets warmed up by adiabatic process. This dry air may melt the snow in a short time. Local Winds Local differences of temperature and pressure produce local winds. Such winds are local in extent and are confined to the lowest levels of the troposphere. Some examples of local winds are discussed below. Loo Harmful Wind In the plains of northern India and Pakistan, sometimes a very hot and dry wind blows from the west in the months of May and June, usually in the afternoons. It is known as Its temperature invariably ranges between 45°C and 50°C. It may cause sunstroke to people. Foehn or Fohn Beneficial Wind Foehn is a hot wind of local importance in the Alps. It is a strong, gusty, dry and warm wind which develops on the leeward side of a mountain range. As the windward side takes away whatever moisture there is in the incoming wind in the form of orographic precipitation, the air that descends on the leeward side is dry and warm (Katabatic Wind). The temperature of the wind varies between 15°C and 20°C. The wind helps animal grazing by melting snow and aids the ripening of grapes. Chinook Beneficial Wind Foehn like winds in USA and Canada move down the west slopes of the Rockies and are known as It is beneficial to ranchers east of the Rockies as it keeps the grasslands clear of snow during much of the winter. Mistral Harmful Wind Mistral is one of the local names given to such winds that blow from the Alps over France towards the Mediterranean Sea. It is channeled through the Rhine valley. It is very cold and dry with a high speed. It brings blizzards into southern France. Sirocco Harmful Wind Sirocco is a Mediterranean wind that comes from the Sahara and reaches hurricane speeds in North Africa and Southern Europe. It arises from a warm, dry, tropical air mass that is pulled northward by low-pressure cells moving eastward across the Mediterranean Sea, with the wind originating in the Arabian or Sahara deserts. The hotter, drier continental air mixes with the cooler, wetter air of the maritime cyclone, and the counter-clockwise circulation of the low propels the mixed air across the southern coasts of Europe. The Sirocco causes dusty dry conditions along the northern coast of Africa, storms in the Mediterranean Sea, and cool wet weather in Europe.

General circulation of the atmosphere The pattern of the movement of the planetary winds is called the general circulation of the atmosphere. The general circulation of the atmosphere also sets in motion the ocean water circulation which influences the earth’s climate. Hadley Cell The air at the Inter Tropical Convergence Zone (ITCZ) rises because of the convection currents caused by low pressure. Low pressure in turn occurs due to high insolation. The winds from the tropics converge at this low pressure zone. The converged air rises along with the convective cell. It reaches the top of the troposphere up to an altitude of 14 km, and moves towards the poles. This causes accumulation of air at about 30° N and S. Part of the accumulated air sinks to the ground and forms a subtropical high. Another reason for sinking is the cooling of air when it reaches 30° N and S latitudes. Down below near the land surface the air flows towards the equator as the easterlies. The easterlies from either side of the equator converge in the Inter Tropical Convergence Zone (ITCZ). Such circulations from the surface upwards and vice-versa are called cells. Such a cell in the tropics is called Hadley Cell. Ferrel Cell In the middle latitudes the circulation is that of sinking cold air that comes from the poles and the rising warm air that blows from the subtropical high. At the surface these winds are called westerlies and the cell is known as the Ferrel cell. Polar Cell At polar latitudes the cold dense air subsides near the poles and blows towards middle latitudes as the polar easterlies. This cell is called the polar cell. These three cells set the pattern for the general circulation of the atmosphere. The transfer of heat energy from lower latitudes to higher latitudes maintains the general circulation. The general circulation of the atmosphere also affects the oceans. The large-scale winds of the atmosphere initiate large and slow moving currents of the ocean. Oceans in turn provide input of energy and water vapors into the air. These interactions take place rather slowly over a large part of the ocean. Walker Cell Warming and cooling of the Pacific Ocean is most important in terms of general atmospheric circulation. The warm water of the central Pacific Ocean slowly drifts towards South American coast and replaces the cool Peruvian current. Such appearance of warm water off the coast of Peru is known as the El Nino. The El Nino event is closely associated with the pressure changes in the Central Pacific and Australia. This change in pressure condition over Pacific is known as the southern oscillation. The combined phenomenon of southern oscillation and El Nino is known as ENSO. In the years when the ENSO is strong, large-scale variations in weather occur over the world. The arid west coast of South America receives heavy rainfall, drought occurs in Australia and sometimes in India and floods in China. This phenomenon is closely monitored and is used for long range forecasting in major parts of the world. (El-Nino in detail later) Classification of Winds Permanent winds or Primary winds or Prevailing winds or Planetary Winds The trade winds, westerlies and easterlies. Secondary or Periodic Winds Seasonal winds: These winds change their direction in different seasons. For example monsoons in India. Periodic winds: Land and sea breeze, mountain and valley breeze. Local winds These blow only during a particular period of the day or year in a small area. Winds like Loo, Mistral, Foehn, Bora. Primary Winds or Prevailing Winds or Permanent Winds or Planetary Winds These are the planetary winds which blow extensively over continents and oceans. The two most well- understood and significant winds for climate and human activities are trade winds and westerly winds. Trade Winds The trade winds are those blowing from the sub-tropical high pressure areas towards the equatorial low pressure belt. Therefore, these are confined to a region between 30°N and 30°S throughout the earth’s surface. They flow as the north-eastern trades in the northern hemisphere and the south-eastern trades in the southern hemisphere. This deflection in their ideally expected north-south direction is explained on the basis of Coriolis force and Farrells law. Trade winds are descending and stable in areas of their origin (sub-tropical high pressure belt), and as they reach the equator, they become humid and warmer after picking up moisture on their way. The trade winds from two hemispheres meet at the equator, and due to convergence they rise and cause heavy rainfall. The eastern parts of the trade winds associated with the cool ocean currents are drier and more stable than the western parts of the ocean. Westerlies The westerlies are the winds blowing from the sub-tropical high pressure belts towards the sub polar low pressure belts. They blow from south­west to north-east in the northern hemisphere and north-west to south-east in the southern hemisphere. The westerlies of the southern hemisphere are stronger and persistent due to the vast expanse of water, while those of the northern hemisphere are irregular because of uneven relief of vast land-masses. The westerlies are best developed between 40° and 65°S latitudes. These latitudes are often called Roaring Forties, Furious Fifties, and Shrieking Sixties – dreaded terms for sailors. The poleward boundary of the westerlies is highly fluctuating. There are many seasonal and short-term fluctuations. These winds produce wet spells and variability in weather. Polar easterlies The Polar easterlies are dry, cold prevailing winds blowing from north-east to south-west direction in Northern Hemisphere and south-east to north-west in Southern Hemisphere. They blow from the polar high-pressure areas of the sub-polar lows. Secondary Winds or Periodic Winds These winds change their direction with change in season. Monsoons are the best example of large-scale modification of the planetary wind system. Other examples of periodic winds include land and sea breeze, mountain and valley breeze, cyclones and anticyclones, and air masses. Monsoons Monsoons were traditionally explained as land and sea breezes on a large scale. Thus, they were considered a convectional circulation on a giant scale. The monsoons are characterized by seasonal reversal of wind direction. During summer, the trade winds of southern hemisphere are pulled northwards by an apparent northward movement of the sun and by an intense low pressure core in the north-west of the Indian sub­continent. While crossing the equator, these winds get deflected to their right under the effect of Coriolis force. These winds now approach the Asian landmass as south-west monsoons. Since they travel a long distance over a vast expanse of water, by the time they reach the south-western coast of India, they are over-saturated with moisture and cause heavy rainfall in India and neighboring countries. During winter, these conditions are reversed and a high pressure core is created to the north of the Indian subcontinent. Divergent winds are produced by this anticyclonic movement which travels southwards towards the equator. This movement is enhanced by the apparent southward movement of the sun. These are north-east or winter monsoons which are responsible for some precipitation along the east coast of India. The monsoon winds flow over India , Pakistan, Bangladesh, Myanmar (Burma), Sri Lanka, the Arabian Sea, Bay of Bengal, south­eastern Asia, northern Australia, China and Outside India, in the eastern Asiatic countries, such as China and Japan, the winter monsoon is stronger than the summer monsoon. (we will study about monsoons in detail while studying Indian Climate) Land Breeze and Sea Breeze The land and sea absorb and transfer heat differently. During the day the land heats up faster and becomes warmer than the sea. Therefore, over the land the air rises giving rise to a low pressure area, whereas the sea is relatively cool and the pressure over sea is relatively high. Thus, pressure gradient from sea to land is created and the wind blows from the sea to the land as the sea breeze. In the night the reversal of condition takes place. The land loses heat faster and is cooler than the sea. The pressure gradient is from the land to the sea and hence land breeze results. Valley Breeze and Mountain Breeze In mountainous regions, during the day the slopes get heated up and air moves upslope and to fill the resulting gap the air from the valley blows up the valley. This wind is known as the valley breeze. During the night the slopes get cooled and the dense air descends into the valley as the mountain wind. The cool air, of the high plateaus and ice fields draining into the valley is called katabatic wind. Another type of warm wind (katabatic wind) occurs on the leeward side of the mountain ranges. The moisture in these winds, while crossing the mountain ranges condense and precipitate. When it descends down the leeward side of the slope the dry air gets warmed up by adiabatic process. This dry air may melt the snow in a short time. Local Winds Local differences of temperature and pressure produce local winds. Such winds are local in extent and are confined to the lowest levels of the troposphere. Some examples of local winds are discussed below. Loo Harmful Wind In the plains of northern India and Pakistan, sometimes a very hot and dry wind blows from the west in the months of May and June, usually in the afternoons. It is known as Its temperature invariably ranges between 45°C and 50°C. It may cause sunstroke to people. Foehn or Fohn Beneficial Wind Foehn is a hot wind of local importance in the Alps. It is a strong, gusty, dry and warm wind which develops on the leeward side of a mountain range. As the windward side takes away whatever moisture there is in the incoming wind in the form of orographic precipitation, the air that descends on the leeward side is dry and warm (Katabatic Wind). The temperature of the wind varies between 15°C and 20°C. The wind helps animal grazing by melting snow and aids the ripening of grapes. Chinook Beneficial Wind Foehn like winds in USA and Canada move down the west slopes of the Rockies and are known as It is beneficial to ranchers east of the Rockies as it keeps the grasslands clear of snow during much of the winter. Mistral Harmful Wind Mistral is one of the local names given to such winds that blow from the Alps over France towards the Mediterranean Sea. It is channeled through the Rhine valley. It is very cold and dry with a high speed. It brings blizzards into southern France. Sirocco Harmful Wind Sirocco is a Mediterranean wind that comes from the Sahara and reaches hurricane speeds in North Africa and Southern Europe. It arises from a warm, dry, tropical air mass that is pulled northward by low-pressure cells moving eastward across the Mediterranean Sea, with the wind originating in the Arabian or Sahara deserts. The hotter, drier continental air mixes with the cooler, wetter air of the maritime cyclone, and the counter-clockwise circulation of the low propels the mixed air across the southern coasts of Europe. The Sirocco causes dusty dry conditions along the northern coast of Africa, storms in the Mediterranean Sea, and cool wet weather in Europe.

The best social studies projects available online for free for students in grades k-12, including videos and links to project-based learning resources.

#Abhimanyusir #AbhimanyuDahiya #UlimateGeography 9th Social Science Class 10 Social Science Class 11 Geography Class 12 Geography Previous Year Paper

General circulation of the atmosphere The pattern of the movement of the planetary winds is called the general circulation of the atmosphere. The general circulation of the atmosphere also sets in motion the ocean water circulation which influences the earth’s climate. Hadley Cell The air at the Inter Tropical Convergence Zone (ITCZ) rises because of the convection currents caused by low pressure. Low pressure in turn occurs due to high insolation. The winds from the tropics converge at this low pressure zone. The converged air rises along with the convective cell. It reaches the top of the troposphere up to an altitude of 14 km, and moves towards the poles. This causes accumulation of air at about 30° N and S. Part of the accumulated air sinks to the ground and forms a subtropical high. Another reason for sinking is the cooling of air when it reaches 30° N and S latitudes. Down below near the land surface the air flows towards the equator as the easterlies. The easterlies from either side of the equator converge in the Inter Tropical Convergence Zone (ITCZ). Such circulations from the surface upwards and vice-versa are called cells. Such a cell in the tropics is called Hadley Cell. Ferrel Cell In the middle latitudes the circulation is that of sinking cold air that comes from the poles and the rising warm air that blows from the subtropical high. At the surface these winds are called westerlies and the cell is known as the Ferrel cell. Polar Cell At polar latitudes the cold dense air subsides near the poles and blows towards middle latitudes as the polar easterlies. This cell is called the polar cell. These three cells set the pattern for the general circulation of the atmosphere. The transfer of heat energy from lower latitudes to higher latitudes maintains the general circulation. The general circulation of the atmosphere also affects the oceans. The large-scale winds of the atmosphere initiate large and slow moving currents of the ocean. Oceans in turn provide input of energy and water vapors into the air. These interactions take place rather slowly over a large part of the ocean. Walker Cell Warming and cooling of the Pacific Ocean is most important in terms of general atmospheric circulation. The warm water of the central Pacific Ocean slowly drifts towards South American coast and replaces the cool Peruvian current. Such appearance of warm water off the coast of Peru is known as the El Nino. The El Nino event is closely associated with the pressure changes in the Central Pacific and Australia. This change in pressure condition over Pacific is known as the southern oscillation. The combined phenomenon of southern oscillation and El Nino is known as ENSO. In the years when the ENSO is strong, large-scale variations in weather occur over the world. The arid west coast of South America receives heavy rainfall, drought occurs in Australia and sometimes in India and floods in China. This phenomenon is closely monitored and is used for long range forecasting in major parts of the world. (El-Nino in detail later) Classification of Winds Permanent winds or Primary winds or Prevailing winds or Planetary Winds The trade winds, westerlies and easterlies. Secondary or Periodic Winds Seasonal winds: These winds change their direction in different seasons. For example monsoons in India. Periodic winds: Land and sea breeze, mountain and valley breeze. Local winds These blow only during a particular period of the day or year in a small area. Winds like Loo, Mistral, Foehn, Bora. Primary Winds or Prevailing Winds or Permanent Winds or Planetary Winds These are the planetary winds which blow extensively over continents and oceans. The two most well- understood and significant winds for climate and human activities are trade winds and westerly winds. Trade Winds The trade winds are those blowing from the sub-tropical high pressure areas towards the equatorial low pressure belt. Therefore, these are confined to a region between 30°N and 30°S throughout the earth’s surface. They flow as the north-eastern trades in the northern hemisphere and the south-eastern trades in the southern hemisphere. This deflection in their ideally expected north-south direction is explained on the basis of Coriolis force and Farrells law. Trade winds are descending and stable in areas of their origin (sub-tropical high pressure belt), and as they reach the equator, they become humid and warmer after picking up moisture on their way. The trade winds from two hemispheres meet at the equator, and due to convergence they rise and cause heavy rainfall. The eastern parts of the trade winds associated with the cool ocean currents are drier and more stable than the western parts of the ocean. Westerlies The westerlies are the winds blowing from the sub-tropical high pressure belts towards the sub polar low pressure belts. They blow from south­west to north-east in the northern hemisphere and north-west to south-east in the southern hemisphere. The westerlies of the southern hemisphere are stronger and persistent due to the vast expanse of water, while those of the northern hemisphere are irregular because of uneven relief of vast land-masses. The westerlies are best developed between 40° and 65°S latitudes. These latitudes are often called Roaring Forties, Furious Fifties, and Shrieking Sixties – dreaded terms for sailors. The poleward boundary of the westerlies is highly fluctuating. There are many seasonal and short-term fluctuations. These winds produce wet spells and variability in weather. Polar easterlies The Polar easterlies are dry, cold prevailing winds blowing from north-east to south-west direction in Northern Hemisphere and south-east to north-west in Southern Hemisphere. They blow from the polar high-pressure areas of the sub-polar lows. Secondary Winds or Periodic Winds These winds change their direction with change in season. Monsoons are the best example of large-scale modification of the planetary wind system. Other examples of periodic winds include land and sea breeze, mountain and valley breeze, cyclones and anticyclones, and air masses. Monsoons Monsoons were traditionally explained as land and sea breezes on a large scale. Thus, they were considered a convectional circulation on a giant scale. The monsoons are characterized by seasonal reversal of wind direction. During summer, the trade winds of southern hemisphere are pulled northwards by an apparent northward movement of the sun and by an intense low pressure core in the north-west of the Indian sub­continent. While crossing the equator, these winds get deflected to their right under the effect of Coriolis force. These winds now approach the Asian landmass as south-west monsoons. Since they travel a long distance over a vast expanse of water, by the time they reach the south-western coast of India, they are over-saturated with moisture and cause heavy rainfall in India and neighboring countries. During winter, these conditions are reversed and a high pressure core is created to the north of the Indian subcontinent. Divergent winds are produced by this anticyclonic movement which travels southwards towards the equator. This movement is enhanced by the apparent southward movement of the sun. These are north-east or winter monsoons which are responsible for some precipitation along the east coast of India. The monsoon winds flow over India , Pakistan, Bangladesh, Myanmar (Burma), Sri Lanka, the Arabian Sea, Bay of Bengal, south­eastern Asia, northern Australia, China and Outside India, in the eastern Asiatic countries, such as China and Japan, the winter monsoon is stronger than the summer monsoon. (we will study about monsoons in detail while studying Indian Climate) Land Breeze and Sea Breeze The land and sea absorb and transfer heat differently. During the day the land heats up faster and becomes warmer than the sea. Therefore, over the land the air rises giving rise to a low pressure area, whereas the sea is relatively cool and the pressure over sea is relatively high. Thus, pressure gradient from sea to land is created and the wind blows from the sea to the land as the sea breeze. In the night the reversal of condition takes place. The land loses heat faster and is cooler than the sea. The pressure gradient is from the land to the sea and hence land breeze results. Valley Breeze and Mountain Breeze In mountainous regions, during the day the slopes get heated up and air moves upslope and to fill the resulting gap the air from the valley blows up the valley. This wind is known as the valley breeze. During the night the slopes get cooled and the dense air descends into the valley as the mountain wind. The cool air, of the high plateaus and ice fields draining into the valley is called katabatic wind. Another type of warm wind (katabatic wind) occurs on the leeward side of the mountain ranges. The moisture in these winds, while crossing the mountain ranges condense and precipitate. When it descends down the leeward side of the slope the dry air gets warmed up by adiabatic process. This dry air may melt the snow in a short time. Local Winds Local differences of temperature and pressure produce local winds. Such winds are local in extent and are confined to the lowest levels of the troposphere. Some examples of local winds are discussed below. Loo Harmful Wind In the plains of northern India and Pakistan, sometimes a very hot and dry wind blows from the west in the months of May and June, usually in the afternoons. It is known as Its temperature invariably ranges between 45°C and 50°C. It may cause sunstroke to people. Foehn or Fohn Beneficial Wind Foehn is a hot wind of local importance in the Alps. It is a strong, gusty, dry and warm wind which develops on the leeward side of a mountain range. As the windward side takes away whatever moisture there is in the incoming wind in the form of orographic precipitation, the air that descends on the leeward side is dry and warm (Katabatic Wind). The temperature of the wind varies between 15°C and 20°C. The wind helps animal grazing by melting snow and aids the ripening of grapes. Chinook Beneficial Wind Foehn like winds in USA and Canada move down the west slopes of the Rockies and are known as It is beneficial to ranchers east of the Rockies as it keeps the grasslands clear of snow during much of the winter. Mistral Harmful Wind Mistral is one of the local names given to such winds that blow from the Alps over France towards the Mediterranean Sea. It is channeled through the Rhine valley. It is very cold and dry with a high speed. It brings blizzards into southern France. Sirocco Harmful Wind Sirocco is a Mediterranean wind that comes from the Sahara and reaches hurricane speeds in North Africa and Southern Europe. It arises from a warm, dry, tropical air mass that is pulled northward by low-pressure cells moving eastward across the Mediterranean Sea, with the wind originating in the Arabian or Sahara deserts. The hotter, drier continental air mixes with the cooler, wetter air of the maritime cyclone, and the counter-clockwise circulation of the low propels the mixed air across the southern coasts of Europe. The Sirocco causes dusty dry conditions along the northern coast of Africa, storms in the Mediterranean Sea, and cool wet weather in Europe.

Wayfinder navigators always look for signs of weather at sunrise and sunset. This is when they try to predict the weather for the next 12 hours.

Dive into the wonders of U.S. geography with your children as you embark on a journey of mapping the USA. Discover exciting and educational activities designed to make learning about the country's geography a playful and memorable experience for young minds.

Types of Winds: Permanent, Secondary & Local Winds

This is a brief description of the structure of planet Earth, written specifically to help educate curious children.

Craft and activities to go with Jack and the Beanstalk

Skara Brae is a stone-built Neolithic settlement, located on the Bay of Skaill on the west coast of Mainland, the largest island in the Orkney

Abhimanyusir.blogspot.com #AbhimanyuDahiya #UlimateGeography #Abhimanyusir Class 10 Social Science Class 12 Geography Previous Year Paper

General circulation of the atmosphere The pattern of the movement of the planetary winds is called the general circulation of the atmosphere. The general circulation of the atmosphere also sets in motion the ocean water circulation which influences the earth’s climate. Hadley Cell The air at the Inter Tropical Convergence Zone (ITCZ) rises because of the convection currents caused by low pressure. Low pressure in turn occurs due to high insolation. The winds from the tropics converge at this low pressure zone. The converged air rises along with the convective cell. It reaches the top of the troposphere up to an altitude of 14 km, and moves towards the poles. This causes accumulation of air at about 30° N and S. Part of the accumulated air sinks to the ground and forms a subtropical high. Another reason for sinking is the cooling of air when it reaches 30° N and S latitudes. Down below near the land surface the air flows towards the equator as the easterlies. The easterlies from either side of the equator converge in the Inter Tropical Convergence Zone (ITCZ). Such circulations from the surface upwards and vice-versa are called cells. Such a cell in the tropics is called Hadley Cell. Ferrel Cell In the middle latitudes the circulation is that of sinking cold air that comes from the poles and the rising warm air that blows from the subtropical high. At the surface these winds are called westerlies and the cell is known as the Ferrel cell. Polar Cell At polar latitudes the cold dense air subsides near the poles and blows towards middle latitudes as the polar easterlies. This cell is called the polar cell. These three cells set the pattern for the general circulation of the atmosphere. The transfer of heat energy from lower latitudes to higher latitudes maintains the general circulation. The general circulation of the atmosphere also affects the oceans. The large-scale winds of the atmosphere initiate large and slow moving currents of the ocean. Oceans in turn provide input of energy and water vapors into the air. These interactions take place rather slowly over a large part of the ocean. Walker Cell Warming and cooling of the Pacific Ocean is most important in terms of general atmospheric circulation. The warm water of the central Pacific Ocean slowly drifts towards South American coast and replaces the cool Peruvian current. Such appearance of warm water off the coast of Peru is known as the El Nino. The El Nino event is closely associated with the pressure changes in the Central Pacific and Australia. This change in pressure condition over Pacific is known as the southern oscillation. The combined phenomenon of southern oscillation and El Nino is known as ENSO. In the years when the ENSO is strong, large-scale variations in weather occur over the world. The arid west coast of South America receives heavy rainfall, drought occurs in Australia and sometimes in India and floods in China. This phenomenon is closely monitored and is used for long range forecasting in major parts of the world. (El-Nino in detail later) Classification of Winds Permanent winds or Primary winds or Prevailing winds or Planetary Winds The trade winds, westerlies and easterlies. Secondary or Periodic Winds Seasonal winds: These winds change their direction in different seasons. For example monsoons in India. Periodic winds: Land and sea breeze, mountain and valley breeze. Local winds These blow only during a particular period of the day or year in a small area. Winds like Loo, Mistral, Foehn, Bora. Primary Winds or Prevailing Winds or Permanent Winds or Planetary Winds These are the planetary winds which blow extensively over continents and oceans. The two most well- understood and significant winds for climate and human activities are trade winds and westerly winds. Trade Winds The trade winds are those blowing from the sub-tropical high pressure areas towards the equatorial low pressure belt. Therefore, these are confined to a region between 30°N and 30°S throughout the earth’s surface. They flow as the north-eastern trades in the northern hemisphere and the south-eastern trades in the southern hemisphere. This deflection in their ideally expected north-south direction is explained on the basis of Coriolis force and Farrells law. Trade winds are descending and stable in areas of their origin (sub-tropical high pressure belt), and as they reach the equator, they become humid and warmer after picking up moisture on their way. The trade winds from two hemispheres meet at the equator, and due to convergence they rise and cause heavy rainfall. The eastern parts of the trade winds associated with the cool ocean currents are drier and more stable than the western parts of the ocean. Westerlies The westerlies are the winds blowing from the sub-tropical high pressure belts towards the sub polar low pressure belts. They blow from south­west to north-east in the northern hemisphere and north-west to south-east in the southern hemisphere. The westerlies of the southern hemisphere are stronger and persistent due to the vast expanse of water, while those of the northern hemisphere are irregular because of uneven relief of vast land-masses. The westerlies are best developed between 40° and 65°S latitudes. These latitudes are often called Roaring Forties, Furious Fifties, and Shrieking Sixties – dreaded terms for sailors. The poleward boundary of the westerlies is highly fluctuating. There are many seasonal and short-term fluctuations. These winds produce wet spells and variability in weather. Polar easterlies The Polar easterlies are dry, cold prevailing winds blowing from north-east to south-west direction in Northern Hemisphere and south-east to north-west in Southern Hemisphere. They blow from the polar high-pressure areas of the sub-polar lows. Secondary Winds or Periodic Winds These winds change their direction with change in season. Monsoons are the best example of large-scale modification of the planetary wind system. Other examples of periodic winds include land and sea breeze, mountain and valley breeze, cyclones and anticyclones, and air masses. Monsoons Monsoons were traditionally explained as land and sea breezes on a large scale. Thus, they were considered a convectional circulation on a giant scale. The monsoons are characterized by seasonal reversal of wind direction. During summer, the trade winds of southern hemisphere are pulled northwards by an apparent northward movement of the sun and by an intense low pressure core in the north-west of the Indian sub­continent. While crossing the equator, these winds get deflected to their right under the effect of Coriolis force. These winds now approach the Asian landmass as south-west monsoons. Since they travel a long distance over a vast expanse of water, by the time they reach the south-western coast of India, they are over-saturated with moisture and cause heavy rainfall in India and neighboring countries. During winter, these conditions are reversed and a high pressure core is created to the north of the Indian subcontinent. Divergent winds are produced by this anticyclonic movement which travels southwards towards the equator. This movement is enhanced by the apparent southward movement of the sun. These are north-east or winter monsoons which are responsible for some precipitation along the east coast of India. The monsoon winds flow over India , Pakistan, Bangladesh, Myanmar (Burma), Sri Lanka, the Arabian Sea, Bay of Bengal, south­eastern Asia, northern Australia, China and Outside India, in the eastern Asiatic countries, such as China and Japan, the winter monsoon is stronger than the summer monsoon. (we will study about monsoons in detail while studying Indian Climate) Land Breeze and Sea Breeze The land and sea absorb and transfer heat differently. During the day the land heats up faster and becomes warmer than the sea. Therefore, over the land the air rises giving rise to a low pressure area, whereas the sea is relatively cool and the pressure over sea is relatively high. Thus, pressure gradient from sea to land is created and the wind blows from the sea to the land as the sea breeze. In the night the reversal of condition takes place. The land loses heat faster and is cooler than the sea. The pressure gradient is from the land to the sea and hence land breeze results. Valley Breeze and Mountain Breeze In mountainous regions, during the day the slopes get heated up and air moves upslope and to fill the resulting gap the air from the valley blows up the valley. This wind is known as the valley breeze. During the night the slopes get cooled and the dense air descends into the valley as the mountain wind. The cool air, of the high plateaus and ice fields draining into the valley is called katabatic wind. Another type of warm wind (katabatic wind) occurs on the leeward side of the mountain ranges. The moisture in these winds, while crossing the mountain ranges condense and precipitate. When it descends down the leeward side of the slope the dry air gets warmed up by adiabatic process. This dry air may melt the snow in a short time. Local Winds Local differences of temperature and pressure produce local winds. Such winds are local in extent and are confined to the lowest levels of the troposphere. Some examples of local winds are discussed below. Loo Harmful Wind In the plains of northern India and Pakistan, sometimes a very hot and dry wind blows from the west in the months of May and June, usually in the afternoons. It is known as Its temperature invariably ranges between 45°C and 50°C. It may cause sunstroke to people. Foehn or Fohn Beneficial Wind Foehn is a hot wind of local importance in the Alps. It is a strong, gusty, dry and warm wind which develops on the leeward side of a mountain range. As the windward side takes away whatever moisture there is in the incoming wind in the form of orographic precipitation, the air that descends on the leeward side is dry and warm (Katabatic Wind). The temperature of the wind varies between 15°C and 20°C. The wind helps animal grazing by melting snow and aids the ripening of grapes. Chinook Beneficial Wind Foehn like winds in USA and Canada move down the west slopes of the Rockies and are known as It is beneficial to ranchers east of the Rockies as it keeps the grasslands clear of snow during much of the winter. Mistral Harmful Wind Mistral is one of the local names given to such winds that blow from the Alps over France towards the Mediterranean Sea. It is channeled through the Rhine valley. It is very cold and dry with a high speed. It brings blizzards into southern France. Sirocco Harmful Wind Sirocco is a Mediterranean wind that comes from the Sahara and reaches hurricane speeds in North Africa and Southern Europe. It arises from a warm, dry, tropical air mass that is pulled northward by low-pressure cells moving eastward across the Mediterranean Sea, with the wind originating in the Arabian or Sahara deserts. The hotter, drier continental air mixes with the cooler, wetter air of the maritime cyclone, and the counter-clockwise circulation of the low propels the mixed air across the southern coasts of Europe. The Sirocco causes dusty dry conditions along the northern coast of Africa, storms in the Mediterranean Sea, and cool wet weather in Europe.

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This post may contain affiliate links. Thank you for supporting my blog and homeschool! See my full Disclosure statement for more information. When I first started homeschooling my girls the hardest part of it all was not only finding the curriculum that would work best for them. . .it was making up worksheets, tests, and the like. . . Can I get a witness!? I didn't start homeschooling them until Middle School and High School which only added to my stress level. So imagine how excited I was to have an opportunity to review CHSH-Teach.com and their CHSH Download Club!! This product is nothing short of phenomenal!! There is literally something for everyone. The opportunities are endless! The CHSH Download Club is one of the most vast databases of helps I have ever witnessed! With something for any grade level, it won't take you long to find exactly what you were looking for. In fact if you are anything like me, it won't take you long to find something you weren't looking for but will fit your needs exactly! Have you ever heard the saying, "You don't know what you don't know?" Let me just change it up a little bit. . . "Sometimes you don't know what you need until you see it!" That is exactly what happened to me as I browsed through the CHSH Download Club options. With multiple ways to browse for what you need, I double-dog dare you to find nothing that will work for your homeschool!! Give yourself a break and try this website out for yourself!! My daughter needed a science course and I was able to download the entire science book and the teacher's guide!!! WHAT!!?? This was the one we chose for her freshman year, but there are definitely more choices and a different class may suit your needs better. Which is entirely the point of this incredible website! She loves Science and dove right in. Unit 1 caught her interest immediately with this...How are Waffles & Running Shoes Connected? Take a look at the images below. This shows the ease of access to the product as well as the multiple ways you can search for whatever it is you are looking for. I am so glad that I had the opportunity to review this product! There is so much here to help you and your student. I know that as a homeschool parent our goal is to give our children the best education possible. Christian HomeSchool Hub (CHSH) has put together an amazing site to help you do just that! So whether you have one (1) child you are schooling or eight (8), you will find this resource beneficial! In fact this site has me wishing I had more than two thumbs so I could give it a better rating than two thumbs up!! LOL! You don't have to take my word for it. . . check it out for yourself, I have no doubt in my mind that you will love it as much as I do!! Take a few minutes and click the link below to read more reviews, or check them out on their social media links below!! Facebook Group Facebook Page Twitter Pinterest Google+ Group Google Business Page Linked-In Tumblr

General circulation of the atmosphere The pattern of the movement of the planetary winds is called the general circulation of the atmosphere. The general circulation of the atmosphere also sets in motion the ocean water circulation which influences the earth’s climate. Hadley Cell The air at the Inter Tropical Convergence Zone (ITCZ) rises because of the convection currents caused by low pressure. Low pressure in turn occurs due to high insolation. The winds from the tropics converge at this low pressure zone. The converged air rises along with the convective cell. It reaches the top of the troposphere up to an altitude of 14 km, and moves towards the poles. This causes accumulation of air at about 30° N and S. Part of the accumulated air sinks to the ground and forms a subtropical high. Another reason for sinking is the cooling of air when it reaches 30° N and S latitudes. Down below near the land surface the air flows towards the equator as the easterlies. The easterlies from either side of the equator converge in the Inter Tropical Convergence Zone (ITCZ). Such circulations from the surface upwards and vice-versa are called cells. Such a cell in the tropics is called Hadley Cell. Ferrel Cell In the middle latitudes the circulation is that of sinking cold air that comes from the poles and the rising warm air that blows from the subtropical high. At the surface these winds are called westerlies and the cell is known as the Ferrel cell. Polar Cell At polar latitudes the cold dense air subsides near the poles and blows towards middle latitudes as the polar easterlies. This cell is called the polar cell. These three cells set the pattern for the general circulation of the atmosphere. The transfer of heat energy from lower latitudes to higher latitudes maintains the general circulation. The general circulation of the atmosphere also affects the oceans. The large-scale winds of the atmosphere initiate large and slow moving currents of the ocean. Oceans in turn provide input of energy and water vapors into the air. These interactions take place rather slowly over a large part of the ocean. Walker Cell Warming and cooling of the Pacific Ocean is most important in terms of general atmospheric circulation. The warm water of the central Pacific Ocean slowly drifts towards South American coast and replaces the cool Peruvian current. Such appearance of warm water off the coast of Peru is known as the El Nino. The El Nino event is closely associated with the pressure changes in the Central Pacific and Australia. This change in pressure condition over Pacific is known as the southern oscillation. The combined phenomenon of southern oscillation and El Nino is known as ENSO. In the years when the ENSO is strong, large-scale variations in weather occur over the world. The arid west coast of South America receives heavy rainfall, drought occurs in Australia and sometimes in India and floods in China. This phenomenon is closely monitored and is used for long range forecasting in major parts of the world. (El-Nino in detail later) Classification of Winds Permanent winds or Primary winds or Prevailing winds or Planetary Winds The trade winds, westerlies and easterlies. Secondary or Periodic Winds Seasonal winds: These winds change their direction in different seasons. For example monsoons in India. Periodic winds: Land and sea breeze, mountain and valley breeze. Local winds These blow only during a particular period of the day or year in a small area. Winds like Loo, Mistral, Foehn, Bora. Primary Winds or Prevailing Winds or Permanent Winds or Planetary Winds These are the planetary winds which blow extensively over continents and oceans. The two most well- understood and significant winds for climate and human activities are trade winds and westerly winds. Trade Winds The trade winds are those blowing from the sub-tropical high pressure areas towards the equatorial low pressure belt. Therefore, these are confined to a region between 30°N and 30°S throughout the earth’s surface. They flow as the north-eastern trades in the northern hemisphere and the south-eastern trades in the southern hemisphere. This deflection in their ideally expected north-south direction is explained on the basis of Coriolis force and Farrells law. Trade winds are descending and stable in areas of their origin (sub-tropical high pressure belt), and as they reach the equator, they become humid and warmer after picking up moisture on their way. The trade winds from two hemispheres meet at the equator, and due to convergence they rise and cause heavy rainfall. The eastern parts of the trade winds associated with the cool ocean currents are drier and more stable than the western parts of the ocean. Westerlies The westerlies are the winds blowing from the sub-tropical high pressure belts towards the sub polar low pressure belts. They blow from south­west to north-east in the northern hemisphere and north-west to south-east in the southern hemisphere. The westerlies of the southern hemisphere are stronger and persistent due to the vast expanse of water, while those of the northern hemisphere are irregular because of uneven relief of vast land-masses. The westerlies are best developed between 40° and 65°S latitudes. These latitudes are often called Roaring Forties, Furious Fifties, and Shrieking Sixties – dreaded terms for sailors. The poleward boundary of the westerlies is highly fluctuating. There are many seasonal and short-term fluctuations. These winds produce wet spells and variability in weather. Polar easterlies The Polar easterlies are dry, cold prevailing winds blowing from north-east to south-west direction in Northern Hemisphere and south-east to north-west in Southern Hemisphere. They blow from the polar high-pressure areas of the sub-polar lows. Secondary Winds or Periodic Winds These winds change their direction with change in season. Monsoons are the best example of large-scale modification of the planetary wind system. Other examples of periodic winds include land and sea breeze, mountain and valley breeze, cyclones and anticyclones, and air masses. Monsoons Monsoons were traditionally explained as land and sea breezes on a large scale. Thus, they were considered a convectional circulation on a giant scale. The monsoons are characterized by seasonal reversal of wind direction. During summer, the trade winds of southern hemisphere are pulled northwards by an apparent northward movement of the sun and by an intense low pressure core in the north-west of the Indian sub­continent. While crossing the equator, these winds get deflected to their right under the effect of Coriolis force. These winds now approach the Asian landmass as south-west monsoons. Since they travel a long distance over a vast expanse of water, by the time they reach the south-western coast of India, they are over-saturated with moisture and cause heavy rainfall in India and neighboring countries. During winter, these conditions are reversed and a high pressure core is created to the north of the Indian subcontinent. Divergent winds are produced by this anticyclonic movement which travels southwards towards the equator. This movement is enhanced by the apparent southward movement of the sun. These are north-east or winter monsoons which are responsible for some precipitation along the east coast of India. The monsoon winds flow over India , Pakistan, Bangladesh, Myanmar (Burma), Sri Lanka, the Arabian Sea, Bay of Bengal, south­eastern Asia, northern Australia, China and Outside India, in the eastern Asiatic countries, such as China and Japan, the winter monsoon is stronger than the summer monsoon. (we will study about monsoons in detail while studying Indian Climate) Land Breeze and Sea Breeze The land and sea absorb and transfer heat differently. During the day the land heats up faster and becomes warmer than the sea. Therefore, over the land the air rises giving rise to a low pressure area, whereas the sea is relatively cool and the pressure over sea is relatively high. Thus, pressure gradient from sea to land is created and the wind blows from the sea to the land as the sea breeze. In the night the reversal of condition takes place. The land loses heat faster and is cooler than the sea. The pressure gradient is from the land to the sea and hence land breeze results. Valley Breeze and Mountain Breeze In mountainous regions, during the day the slopes get heated up and air moves upslope and to fill the resulting gap the air from the valley blows up the valley. This wind is known as the valley breeze. During the night the slopes get cooled and the dense air descends into the valley as the mountain wind. The cool air, of the high plateaus and ice fields draining into the valley is called katabatic wind. Another type of warm wind (katabatic wind) occurs on the leeward side of the mountain ranges. The moisture in these winds, while crossing the mountain ranges condense and precipitate. When it descends down the leeward side of the slope the dry air gets warmed up by adiabatic process. This dry air may melt the snow in a short time. Local Winds Local differences of temperature and pressure produce local winds. Such winds are local in extent and are confined to the lowest levels of the troposphere. Some examples of local winds are discussed below. Loo Harmful Wind In the plains of northern India and Pakistan, sometimes a very hot and dry wind blows from the west in the months of May and June, usually in the afternoons. It is known as Its temperature invariably ranges between 45°C and 50°C. It may cause sunstroke to people. Foehn or Fohn Beneficial Wind Foehn is a hot wind of local importance in the Alps. It is a strong, gusty, dry and warm wind which develops on the leeward side of a mountain range. As the windward side takes away whatever moisture there is in the incoming wind in the form of orographic precipitation, the air that descends on the leeward side is dry and warm (Katabatic Wind). The temperature of the wind varies between 15°C and 20°C. The wind helps animal grazing by melting snow and aids the ripening of grapes. Chinook Beneficial Wind Foehn like winds in USA and Canada move down the west slopes of the Rockies and are known as It is beneficial to ranchers east of the Rockies as it keeps the grasslands clear of snow during much of the winter. Mistral Harmful Wind Mistral is one of the local names given to such winds that blow from the Alps over France towards the Mediterranean Sea. It is channeled through the Rhine valley. It is very cold and dry with a high speed. It brings blizzards into southern France. Sirocco Harmful Wind Sirocco is a Mediterranean wind that comes from the Sahara and reaches hurricane speeds in North Africa and Southern Europe. It arises from a warm, dry, tropical air mass that is pulled northward by low-pressure cells moving eastward across the Mediterranean Sea, with the wind originating in the Arabian or Sahara deserts. The hotter, drier continental air mixes with the cooler, wetter air of the maritime cyclone, and the counter-clockwise circulation of the low propels the mixed air across the southern coasts of Europe. The Sirocco causes dusty dry conditions along the northern coast of Africa, storms in the Mediterranean Sea, and cool wet weather in Europe.

I'm so sorry - I have been derelict in my blogging duties. I have lots of excuses why I've been absent lately, but today I'll choose just one to take the blame (because taking responsibility myself would be just too grown up of a thing to do, and it's always easier to blame it on something else). I've been volunteering at Little K's school helping to decorate and set up for our Bi-annual Book Fair with my friend Marni. We were just talking the other day about how we got roped into this...errr I mean how we ended up volunteering for this job? The truth is, it's fun to do, we love working with the Media Staff (Hi Stacey) and it's a creative outlet. But it is a lot of work, and I'm happy to say, we are on track for a fantastic Grand Opening on Friday. This years theme is "Destination: Book Fair. Read Around the World". This is a close up of the main bulletin board inside the Media Center where the Book Fair is set up. Those red balls are Giant Push Pins marking the cities on our World Tour. We can't take credit for all the clever decorations. Scholastic puts out a fantastic "How To" kit and even includes on-line templates and patterns for many of the ideas. Although, I have to admit, we often don't use them...because being the perfectionists that Marni and I both are...we think we can do better on our own, and so we sometimes try. We made invitations for the Staff that looked like Passports. We try to keep the materials as low cost as possible, so the invites were made simply from construction paper and a few scrapbooking tools (punches and corner rounder). The "visa" stamps were created using MS Word. The main entrance was decorated with images of children from various nations, with their countries flag and native greeting. The Teachers Wish board is for families to purchase books to donate to the classroom libraries. Teachers fill out "request" of books they would like at the Staff Preview, so for the Book Fair opening, the suitcase pockets will be filled with wish list cards. Scholastic provided a template for the suitcase pockets, but we chose to use a similar die cut from the scrapbook store. Much faster than cutting them all out by hand. The tables are decorated with globes already owned by the school. For several weeks the students have been coming in during free time and coloring Flags from all Nations. They were strung in banners above the book display tables. Our attempt at a Hot Air Balloon behind the cashier table. Take another look - can you see it now? Bulletin board borders were added to the cases and embellished with flags (found on a free clip art site and printed on cardstock). Kids activities include Guessing Jars filled with Italian Pasta, Chinese Fortune Cookies and Mexican Tortilla Chips. Hopefully you'll understand what I've been keeping busy with lately. My mom has also recently arrived for a visit, and we'll soon be off on a little road trip. But I have lots of projects lined up for Mum and I to do while she's here, so we'll be back to posting with a vengeance soon.

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