Notes On Climatic Controls - CBSE Class 9 Geography
The day-to-day changes that we experience are referred to as weather. Weather is the state of the atmosphere of a particular area at any point of time. Atmospheric conditions that describe the weather include elements like temperature, precipitation, pressure, wind and humidity. During a year, the weather changes in cycles, the cyclic changes in the atmospheric conditions are called seasons. By observing the weather pattern for longer periods, usually over 30 years, the climate of a place can also be determined. The basic elements of weather are wind, temperature, air pressure, precipitation and moisture. Climate describes the long-term pattern of weather that generally prevails over an area. Based on climatic differences, the world can be divided into a number of climatic regions. Each climatic region has its own characteristic vegetation and wildlife. The climatic conditions also influence the lifestyles of the people living in these regions. The factors affecting the climate of a place are referred to as controls and are latitude, altitude, pressure and wind system, distance from the sea, ocean currents, and relief features. Altitude is another factor controlling the climate of a place. Altitude refers to the height a place above sea level.  The higher one travels into the troposphere, the lower the temperature becomes. The rate at which the temperature drops is known as the lapse rate. The variations in air temperature control the pressure and wind system of a place. Warm air rises, creating low pressure areas, while cold air sinks, creating high pressure areas. As a result, winds blow outward from a high pressure location towards lower pressures. The differences in air pressures near the equator and the poles are the main factors that influence global pressure and wind systems. In India, the Tropic of Cancer passes through the central part of the country, from the Rann of Kutch in the west to Mizoram in the east. India has both tropical and subtropical climates. The distance of a place from the sea is another important factor that regulates the climate of a place. As the distance from the sea increases the weather conditions become extreme. Places away from the sea have very hot summers and very cold winters. This condition is known as continentality. Another important control of climate is the circulation of water and air. The air in the atmosphere and the water in the oceans are in constant motion, distributing heat around the world in regular patterns. Warm air and water move towards the poles, while cool air and water move towards the equator. Another major control of climate is the relief of a place. Mountains often act as natural barriers for wind and moisture, affecting the climate of the areas around it. The Himalayas influence the climate of the Indian subcontinent by protecting it from the cold air mass of Central Asia. The climate and related weather conditions in India are controlled by the following atmospheric conditions: Pressure and surface winds, Upper air circulation, Western cyclonic disturbances and tropical cyclones. The earth’s rotation causes the Coriolis force, which tends to turn the flow of air. Jet streams are rivers of wind that blow horizontally through the upper layers of the troposphere, generally from west to east. The movement of water in the oceans is called currents.

#### Summary

The day-to-day changes that we experience are referred to as weather. Weather is the state of the atmosphere of a particular area at any point of time. Atmospheric conditions that describe the weather include elements like temperature, precipitation, pressure, wind and humidity. During a year, the weather changes in cycles, the cyclic changes in the atmospheric conditions are called seasons. By observing the weather pattern for longer periods, usually over 30 years, the climate of a place can also be determined. The basic elements of weather are wind, temperature, air pressure, precipitation and moisture. Climate describes the long-term pattern of weather that generally prevails over an area. Based on climatic differences, the world can be divided into a number of climatic regions. Each climatic region has its own characteristic vegetation and wildlife. The climatic conditions also influence the lifestyles of the people living in these regions. The factors affecting the climate of a place are referred to as controls and are latitude, altitude, pressure and wind system, distance from the sea, ocean currents, and relief features. Altitude is another factor controlling the climate of a place. Altitude refers to the height a place above sea level.  The higher one travels into the troposphere, the lower the temperature becomes. The rate at which the temperature drops is known as the lapse rate. The variations in air temperature control the pressure and wind system of a place. Warm air rises, creating low pressure areas, while cold air sinks, creating high pressure areas. As a result, winds blow outward from a high pressure location towards lower pressures. The differences in air pressures near the equator and the poles are the main factors that influence global pressure and wind systems. In India, the Tropic of Cancer passes through the central part of the country, from the Rann of Kutch in the west to Mizoram in the east. India has both tropical and subtropical climates. The distance of a place from the sea is another important factor that regulates the climate of a place. As the distance from the sea increases the weather conditions become extreme. Places away from the sea have very hot summers and very cold winters. This condition is known as continentality. Another important control of climate is the circulation of water and air. The air in the atmosphere and the water in the oceans are in constant motion, distributing heat around the world in regular patterns. Warm air and water move towards the poles, while cool air and water move towards the equator. Another major control of climate is the relief of a place. Mountains often act as natural barriers for wind and moisture, affecting the climate of the areas around it. The Himalayas influence the climate of the Indian subcontinent by protecting it from the cold air mass of Central Asia. The climate and related weather conditions in India are controlled by the following atmospheric conditions: Pressure and surface winds, Upper air circulation, Western cyclonic disturbances and tropical cyclones. The earth’s rotation causes the Coriolis force, which tends to turn the flow of air. Jet streams are rivers of wind that blow horizontally through the upper layers of the troposphere, generally from west to east. The movement of water in the oceans is called currents.

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