Climates of India

Chapter Overview

India has a monsoon type of climate, yet temperature and rainfall vary greatly among regions and seasons. Latitude, altitude, distance from the sea, relief and the movement of winds help explain these variations.

Learning Objectives

• describe India's main seasonal cycle;
• explain major controls of climate;
• interpret regional temperature and rainfall contrasts;
• connect climate with agriculture, water and disaster preparedness.

Key Concepts

| Climate control | General influence | |---|---| | Latitude | Changes the angle and duration of solar heating. | | Altitude | Higher places are generally cooler than nearby lowlands. | | Distance from sea | Coastal locations usually have a smaller temperature range than interiors. | | Relief | Mountains redirect winds and can produce rain-shadow areas. | | Winds and pressure | Seasonal circulation carries or removes moisture. |

Detailed Explanation

Seasons

India's broad seasonal cycle includes the cold weather season, hot weather season, southwest monsoon season, and retreating or post-monsoon season. Their timing and intensity vary regionally; seasons do not begin everywhere on the same date.

The monsoon

The word monsoon refers to a seasonal reversal or major shift in winds. During summer, strong heating over the subcontinent contributes to low pressure, and moisture-bearing winds bring widespread rain. The Arabian Sea and Bay of Bengal branches are influenced by relief. The monsoon advances in stages and may include wet spells and “breaks”.

Uneven rainfall

Windward slopes often receive heavy rain as moist air rises and cools. Areas on the leeward side may lie in a rain shadow. Western Rajasthan is comparatively dry, while parts of north-eastern India receive exceptionally high rainfall. Tamil Nadu receives an important share of its rain during the retreating monsoon, when winds gather moisture over the Bay of Bengal.

Climate and society

Farm calendars, water storage, clothing and buildings respond to climate. A weak, delayed or excessive monsoon can affect crops and water supplies. Heat waves, floods, droughts and cyclones require reliable warnings, resilient infrastructure and community preparation.

Important Definitions

• Monsoon: a seasonal change in wind circulation, especially associated in South Asia with distinct wet and dry seasons.
• Rain shadow: a relatively dry area on the sheltered side of a mountain barrier.
• Continentality: stronger seasonal temperature range away from the moderating influence of the sea.
• Cyclone: a low-pressure system with winds circulating around its centre.

Worked Example

Question: Why may Mumbai have a smaller annual temperature range than Delhi?

Answer: Mumbai's coastal position allows the sea to moderate heating and cooling because water changes temperature more slowly than land. Delhi is inland and experiences greater continental influence.

Common Mistakes

• Saying all of India has the same four seasons and rainfall.
• Explaining the monsoon only as “sea breeze on a large scale”.
• Confusing a short drought with a permanently arid climate.

Quick Revision

• India's climate shows a strong seasonal monsoon rhythm.
• Relief, winds and location create large regional contrasts.
• The southwest monsoon supplies much, but not all, of India's rain.
• Climate knowledge supports farming, health and hazard preparedness.

Practice Questions

1. Name two controls of climate.
2. What is a rain-shadow region?
3. Why do coastal areas often have an equable climate?
4. Why is monsoon forecasting socially important?

Answers and Explanations

1. Any two of latitude, altitude, distance from sea, relief and wind-pressure systems.
2. A relatively dry area on the leeward side of mountains after air has lost much of its moisture.
3. The sea heats and cools slowly and moderates nearby air temperatures.
4. Farming, reservoirs, transport and disaster planning depend on the timing and amount of rain.