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Questions and Answers
What does atmospheric pressure refer to?
What does atmospheric pressure refer to?
Which unit is commonly used to measure atmospheric pressure?
Which unit is commonly used to measure atmospheric pressure?
What is the pressure gradient?
What is the pressure gradient?
How does atmospheric pressure change with altitude?
How does atmospheric pressure change with altitude?
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Which factor is NOT mentioned as affecting atmospheric pressure?
Which factor is NOT mentioned as affecting atmospheric pressure?
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What effect does increased temperature have on atmospheric pressure?
What effect does increased temperature have on atmospheric pressure?
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Why does humid air exert less pressure than dry air?
Why does humid air exert less pressure than dry air?
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Which pressure belt is characterized by low pressure and intense heating due to vertical sun rays?
Which pressure belt is characterized by low pressure and intense heating due to vertical sun rays?
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What is the primary characteristic of the doldrums?
What is the primary characteristic of the doldrums?
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Where are the sub-tropical high-pressure belts located?
Where are the sub-tropical high-pressure belts located?
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What causes the shifting of pressure belts?
What causes the shifting of pressure belts?
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What characterizes the Polar Highs?
What characterizes the Polar Highs?
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How does the Coriolis Effect influence wind?
How does the Coriolis Effect influence wind?
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Which type of winds are known for blowing steadily throughout the year?
Which type of winds are known for blowing steadily throughout the year?
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What defines the trade winds?
What defines the trade winds?
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What is the primary cause of wind according to the content?
What is the primary cause of wind according to the content?
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What causes the South-East Trade Winds in the Southern Hemisphere?
What causes the South-East Trade Winds in the Southern Hemisphere?
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Which of the following deserts are located on the western margins of continents within tropical latitudes?
Which of the following deserts are located on the western margins of continents within tropical latitudes?
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What is a defining characteristic of Trade Winds?
What is a defining characteristic of Trade Winds?
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What type of winds are the Westerlies classified as?
What type of winds are the Westerlies classified as?
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Which wind originates from the polar regions and moves towards the Circum-polar Low Pressure Zone?
Which wind originates from the polar regions and moves towards the Circum-polar Low Pressure Zone?
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During which season does the summer monsoon occur?
During which season does the summer monsoon occur?
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Which of the following statements is true about local winds?
Which of the following statements is true about local winds?
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What phenomenon occurs when a warm wind develops on the leeward side of the Alps?
What phenomenon occurs when a warm wind develops on the leeward side of the Alps?
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Study Notes
Atmospheric Pressure
- Refers to the force per unit area exerted by the weight of air above a surface
- Average pressure at sea level is 1013.25 millibars (mb) or 760 mm
- Variations in pressure cause horizontal wind movement
Measurement of Pressure
- Measured in millibars
- Variations shown on maps using isobars (lines connecting areas of equal pressure)
- Isobars show pressure gradients
Pressure Gradient
- Rate of pressure change between two points
- Steeper gradients mean faster wind speeds
Factors Affecting Atmospheric Pressure
1. Altitude
- Atmospheric pressure decreases with increasing altitude
- Higher altitude means thinner, less dense air
- Lower oxygen and pressure at high altitudes can lead to problems like decompression sickness
- Mountain climbers often use supplemental oxygen
2. Temperature
- Atmospheric pressure decreases with increasing temperature
- Higher temperatures cause air molecules to move further apart, reducing density, and thus pressure
3. Water Vapor
- Water vapor (18 g/mol) has a lower molecular weight than average air (29 g/mol)
- Humid air is less dense and exerts less pressure than dry air
4. Rotation of the Earth
- Earth's rotation causes air movement towards the equator
- Equatorial regions receive high solar radiation, making the air warmer, lighter, and rising, creating a low pressure zone
- Air at polar regions is colder and heavier, sinking, creating high pressure zones
World Pressure Belts
- Global horizontal distribution of atmospheric pressure
- Pressure belts are zonal (circular) patterns around the Earth
- Seven pressure belts in total
(i) Equatorial Low-Pressure Belt
- Located 0-5 degrees north and south of the equator
- Intense heating from direct sunlight leads to rising, warm air
- Often called the doldrums due to calm conditions
(ii) Subtropical High-Pressure Belts
- Located approximately 30 degrees north and south of the equator
- Descending air (cooler/denser) creating high-pressure regions
- Also called horse latitudes
(iii) Circum-polar Low-Pressure Belts
- Found between 60-70 degrees latitude in both hemispheres
- Caused by converging winds
(iv) Polar High-Pressure Areas
- Located between 70-90 degrees latitude in both hemispheres
- Extremely low temperatures resulting in descending air and high pressure
- Permanent ice caps are a feature of these regions
Shifting of Pressure Belts
- Earth's tilting (axial inclination) affects pressure belt positions throughout the year
- Pressure belts shift causing seasonal changes in climate
Winds
- Air flows from high to low pressure areas
- Horizontal movement of air is called wind
Factors Affecting Wind Direction/Velocity
1. Pressure Gradient
- The steeper the pressure gradient, the faster the wind speed
2. Coriolis Effect
- Earth's rotation influences wind direction by deflecting them to the right in the Northern Hemisphere and to the left in the Southern Hemisphere
Types of Winds
Permanent Winds
- Blow consistently throughout the year in predictable directions
- Examples: Trade winds, westerlies, and polar easterlies
Periodic Winds
- Change direction periodically with seasons
- Examples: Monsoons
Local Winds
- Restricted to a specific geographic region
- Temperature differences between land and water bodies often create these local winds
- Examples: Sea breezes, land breezes, foehn, and loo
Cyclones
- Region of low pressure with inward-circulating winds
- Often associated with severe weather
Tropical Cyclones
- Strong winds, heavy rainfall, and storm surges
- Centered by a calm eye, surrounded by a vortex
Tornado
- Funnel-shaped cloud extending downward from a thunderstorm
- Small in size but capable of significant damage
Anticyclones
- Region of high pressure with outward-circulating winds
- Generally associated with stable weather conditions
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Description
Explore the concepts of atmospheric pressure, its measurement, and the factors affecting it. This quiz covers key topics such as pressure gradients, altitude effects, and temperature influences on air density. Perfect for students studying earth sciences or meteorology.
