Climatology is an important branch of Physical Geography that studies the climate of the Earth, its elements, distribution, and factors affecting it. Questions related to climate, atmospheric circulation, winds, rainfall, pressure belts, cyclones, and climatic regions are frequently asked in NDA and CDS examinations. A clear understanding of climatology helps candidates answer both static and current geography questions effectively.
NDA & CDS 2 2026 Exam GK – Geography – Climatology – Class 1
What is Climatology?
Climatology is the scientific study of climate and long-term weather patterns. While weather refers to atmospheric conditions over a short period, climate represents the average weather conditions of a place over a period of at least 30 years.
Difference Between Weather and Climate
| Weather | Climate |
|---|---|
| Short-term atmospheric condition | Long-term average atmospheric condition |
| Changes frequently | Relatively stable over decades |
| Forecast for days or weeks | Studied over 30 years or more |
| Example: Rain today | Example: Tropical monsoon climate |
Elements of Climate
The climate of a region is determined by several atmospheric elements:
1. Temperature
Temperature measures the degree of hotness or coldness of the atmosphere. It is influenced by latitude, altitude, ocean currents, and distance from the sea.
2. Atmospheric Pressure
Atmospheric pressure is the force exerted by the weight of air on the Earth’s surface. It decreases with increasing altitude.
3. Wind
Wind is the horizontal movement of air from high-pressure areas to low-pressure areas.
4. Humidity
Humidity refers to the amount of water vapour present in the atmosphere.
5. Precipitation
It includes all forms of moisture falling from the atmosphere, such as rain, snow, sleet, and hail.
6. Cloud Cover
Clouds influence temperature, rainfall, and atmospheric conditions.
Factors Affecting Climate
Latitude
Regions near the Equator receive more solar energy and are warmer than regions near the poles.
Altitude
Temperature decreases with height at an average rate of 6.5°C per 1000 metres.
Distance from the Sea
Coastal areas experience moderate climates, while interiors have extreme climates.
Ocean Currents
Warm currents raise temperatures, whereas cold currents lower temperatures along coastal regions.
Relief Features
Mountains act as barriers to winds and influence rainfall patterns.
Heat Budget of the Earth
The Earth receives energy from the Sun in the form of shortwave radiation and loses energy through longwave terrestrial radiation.
The balance between incoming solar radiation and outgoing terrestrial radiation is known as the Heat Budget of the Earth.
Important Facts
- Equatorial regions receive surplus heat.
- Polar regions experience heat deficiency.
- Atmospheric and oceanic circulation help redistribute heat across the globe.
Atmospheric Pressure Belts
The Earth has seven major pressure belts:
1. Equatorial Low Pressure Belt (0°)
- High temperature.
- Rising air currents.
- Heavy rainfall.
2. Subtropical High Pressure Belts (30° N & S)
- Descending air.
- Dry conditions.
- Location of major deserts.
3. Subpolar Low Pressure Belts (60° N & S)
- Meeting zone of warm and cold air masses.
- Frequent storms.
4. Polar High Pressure Belts (90° N & S)
- Extremely cold conditions.
- Descending air masses.
Planetary Winds
Trade Winds
- Blow from subtropical highs toward the equatorial low-pressure belt.
- Deflected due to the Coriolis force.
- Important for maritime navigation.
Westerlies
- Blow from west to east between 30° and 60° latitudes.
- Strongest in the Southern Hemisphere.
Polar Easterlies
- Blow from polar highs toward subpolar lows.
- Cold and dry in nature.
Local Winds
Loo
- Hot and dry wind.
- Blows in northern India during summer.
Chinook
- Warm, dry wind on the eastern slopes of the Rocky Mountains.
- Known as the “Snow Eater.”
Foehn
- Warm and dry wind in the Alps region.
Mistral
- Cold wind blowing through southern France.
Sirocco
- Hot, dusty wind originating from the Sahara Desert.
Jet Streams
Jet streams are narrow bands of high-speed winds found in the upper atmosphere.
Characteristics
- Flow from west to east.
- Speeds often exceed 300 km/h.
- Influence weather systems and aviation routes.
Types
- Polar Front Jet Stream
- Subtropical Jet Stream
The Subtropical Jet Stream significantly influences the Indian Monsoon.
Humidity and Condensation
Humidity
Amount of water vapour present in the atmosphere.
Types
- Absolute Humidity
- Relative Humidity
- Specific Humidity
Condensation Forms
- Dew
- Frost
- Fog
- Clouds
Types of Rainfall
1. Convectional Rainfall
- Caused by intense heating of the Earth’s surface.
- Common in equatorial regions.
2. Orographic Rainfall
- Occurs when moist air rises over mountains.
- Windward side receives heavy rainfall.
- Leeward side experiences rain shadow conditions.
3. Cyclonic Rainfall
- Produced by the meeting of warm and cold air masses.
- Common in temperate regions.
