Atmospheric Pressure Belts
Delhi Police & SSC Exams
1. Introduction
The Earth's atmosphere is not uniform — it has different pressure zones formed due to uneven heating of the Earth's surface by the Sun.
These zones are known as Pressure Belts and they play a vital role in creating winds, rainfall, and global weather patterns.
Memory Tricks:
Low → High → Low → High → Low → High (From Equator to Poles)
Key Concepts:
- Global pressure belt system
- Air movement patterns
- Wind formation and direction
- Climate and weather influences
2. What Is Atmospheric Pressure?
Definition:
Atmospheric Pressure is the weight of the air exerted on the Earth's surface. It decreases with height and is highest at sea level.
Measured by: Barometer
Unit: Millibar (mb) or Hectopascal (hPa)
Key Facts:
Pressure decreases with altitude
Standard sea level pressure: 1013.25 mb
Low pressure = Rising air = Cloudy/rainy weather
High pressure = Sinking air = Clear/dry weather
3. Why Are Pressure Belts Formed?
Unequal Heating
Differential solar heating of Earth's surface
Earth's Rotation
Coriolis effect due to Earth's rotation
Convection Currents
Rising and sinking of air masses
Memory Trick: "HRC → Heating, Rotation, Convection"
4. Major Pressure Belts of the Earth
| No. | Pressure Belt Name | Latitude Range | Pressure Type | Key Feature |
|---|---|---|---|---|
| 1 | Equatorial Low Pressure Belt | 0°–5° N & S | Low | Rising warm air near equator |
| 2 | Subtropical High Pressure Belt | 25°–35° N & S | High | Descending dry air |
| 3 | Subpolar Low Pressure Belt | 55°–65° N & S | Low | Rising warm & cold air meeting |
| 4 | Polar High Pressure Belt | Near 90° N & S | High | Very cold, dense air sinking |
Memory Trick: "E–L, S–H, SP–L, P–H → 'Every Student Studies Patiently'"
5. Global Pressure Belts Diagram
Earth's Pressure Belts (Simplified)
Important: Pressure belts are symmetrical on both sides of the Equator
6. Detailed Explanation of Each Belt
1. Equatorial Low-Pressure Belt (Doldrums)
Found between 0°–5° N & S. Air near the equator is heated, becomes light, and rises upward → creating a low-pressure zone.
Features: Area of calm winds and frequent rainfall
Memory Trick: "Equator = Rising air = Low pressure = Rain"
Also known as: Doldrums ("Calm Zone")
2. Subtropical High-Pressure Belt
Found around 30° N & S. Air that rose at the equator cools and sinks down here, creating high pressure.
Features: Regions are dry → Deserts (e.g., Sahara, Kalahari, Australian Desert)
Memory Trick: "30° = Sinking Air = Dry = Desert"
Also known as: Horse Latitudes
3. Subpolar Low-Pressure Belt
Found near 60° N & S. Warm westerlies meet cold polar winds → rising air → low pressure forms.
Features: Known for cyclonic activities and stormy weather
Memory Trick: "60° = Meeting Winds = Rising Air = Low Pressure"
4. Polar High-Pressure Belt
Found near 90° N & S (Poles). Air is extremely cold and dense, hence it sinks, forming high pressure.
Features: Winds blow outward from poles → Polar Easterlies
Memory Trick: "Poles = Cold = Heavy Air = High Pressure"
7. Relation Between Pressure Belts and Winds
Basic Principle:
Winds always blow from High Pressure → Low Pressure
Global Wind Systems:
Trade Winds (from Subtropical High → Equatorial Low)
Westerlies (from Subtropical High → Subpolar Low)
Polar Easterlies (from Polar High → Subpolar Low)
Wind Flow Pattern:
High Pressure Zones
Low Pressure Zones
Wind Direction
Memory Trick: "H → L = Wind Flow Rule"
8. Shifting of Pressure Belts
Seasonal Movement:
- Pressure belts shift northward in summer
- Pressure belts shift southward in winter
- Due to apparent movement of the Sun
Impact: This shifting causes seasonal changes and influences monsoon winds in India
Movement Pattern:
June: Sun overhead at Tropic of Cancer → Belts shift north
December: Sun overhead at Tropic of Capricorn → Belts shift south
March/September: Sun at Equator → Belts in normal position
Memory Trick: "Sun moves → Belts move → Seasons change"
9. Importance of Pressure Belts
Control global wind systems
Influence ocean currents
Affect rainfall & weather
Responsible for monsoon circulation
Define desert and rainy zones
Influence human settlement patterns
PYQs (Delhi Police, SSC & State Exams)
The equatorial low-pressure belt is also known as —
Options: (a) Trade Wind Belt (b) Westerly Belt (c) Doldrums (d) Horse Latitude
Category: Pressure Belt Names
Show Answer
c) Doldrums
Which pressure belt is associated with desert regions?
Options: (a) Subpolar Low (b) Subtropical High (c) Equatorial Low (d) Polar High
Category: Pressure Belt Features
Show Answer
b) Subtropical High
The area around 30° latitude is known for —
Options: (a) Calm and rainy weather (b) High temperature and humidity (c) Dry and descending air (d) Low-pressure cyclones
Category: Pressure Belt Characteristics
Show Answer
c) Dry and descending air
The polar high-pressure belt is characterized by —
Options: (a) Warm and moist air (b) Cold and dense air (c) Hot and dry air (d) Rising air currents
Category: Polar Belt Features
Show Answer
b) Cold and dense air
Winds blow from —
Options: (a) Low pressure to high pressure (b) High pressure to low pressure (c) Equator to poles only (d) Poles to equator only
Category: Wind Direction Principle
Show Answer
b) High pressure to low pressure
The meeting zone of westerlies and polar easterlies is —
Options: (a) Equatorial Low Belt (b) Subtropical High Belt (c) Subpolar Low Belt (d) Polar High Belt
Category: Wind Systems
Show Answer
c) Subpolar Low Belt
Horse Latitudes are associated with —
Options: (a) Subpolar Low Pressure (b) Subtropical High Pressure (c) Polar High Pressure (d) Equatorial Low Pressure
Category: Alternative Names
Show Answer
b) Subtropical High Pressure
10. Quick Summary Table
| Pressure Belt | Latitude | Pressure | Air Movement | Other Name / Feature |
|---|---|---|---|---|
| Equatorial Low (Doldrums) | 0°–5° | Low | Rising air | Heavy rainfall, calm |
| Subtropical High (Horse Lat.) | 25°–35° | High | Descending air | Deserts, dry winds |
| Subpolar Low | 55°–65° | Low | Rising air | Cyclonic storms |
| Polar High | 90° | High | Descending air | Cold, dry winds |
Final Exam Tips
Remember: Low–High–Low–High–Low–High pattern
Doldrums → Equatorial Low
Horse Latitudes → Subtropical High
Deserts → Found near 30° latitude
Polar = High pressure = Cold air
Winds blow from High → Low pressure
Memory Trick: "LHLHLH – Daring Students Learn Helpful Habits"
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