The physical geography of India

Predict, then check

Think about what happens to moist air when it meets a wall of mountains.

Wind carrying moist air meets a mountain range such as the Western Ghats, and the air has to climb up and over. Which side of the range do you expect to be wetter?

Geography · India's biomes

Which place is it?

Pick a fact, then the place it describes.

8 of 8 still to sort.

A biome is a large community of vegetation and wildlife adapted to a specific climate. India has a range of them.

What you need to know

• Start with where we are: India sits just north of the Equator, in southern Asia.
• Weather is day to day. Climate is the average weather over a long time, usually 30 years or more.
• Most of India has a tropical monsoon climate, with three seasons: summer, the monsoon season and winter.
• India is big, with a varied landscape. It spans several lines of latitude and climate zones, so it isn't in just one.
• Cherrapunjee in north-east India is one of the wettest places on Earth, with about 12 metres of rain a year.
• Climate graphs show average temperature as a line and average rainfall as bars, over a year.
• Going up cools things down. As altitude increases, temperature decreases, so the Himalayas are cooler and can stay snow-covered.
• Have a goOne village is high up in the Himalayas, another is low down on the coast. Which is likely to be cooler, and why?

  The Himalayan village, because it is higher.

  Temperature decreases as altitude increases, so the tempting 'they'd match' guess ignores height.

• Mountains such as the Himalayas and the Western Ghats force air upwards. Rising air cools and causes rain.
• So the windward side gets more rainfall, while the leeward side can be much drier.
• Distance from the sea matters too. Places near India's very long coastline tend to have more moderate, wetter climates than inland.
• Have a goTwo towns, one on the coast and one far inland. Which would you expect to have the wetter, more moderate climate?

  The coastal town.

  Places close to the sea tend to be wetter and more moderate. Inland places don't get that effect.

• A monsoon is a seasonal change in wind direction. It brings a very rainy season or a very dry one.
• Summer first: hot land has low pressure, the cooler ocean has high pressure, so air flows from ocean to land.
• Have a goIn summer the land is hot. Does hot land have high pressure or low pressure?

  Low pressure.

  Low pressure over land and high pressure over the ocean sends air from ocean to land. Swap them and the wind would go the wrong way.

• That's the south-west monsoon, June to September: moisture from the Indian Ocean and heavy rain, about 70 per cent of the year's.
• Winter flips it. The colder land has high pressure, the ocean has low pressure, so winds blow from land to ocean.
• That's the north-east monsoon, October to February: a much drier wind that brings little rain to most of India.
• Have a goWhich monsoon brings most of India's rain: the south-west or the north-east?

  The south-west monsoon, in summer.

  The north-east monsoon is the much drier wind, and it is easy to swap the two over.

• Why it matters: monsoon rain helps farmers grow crops, fills rivers and reservoirs, waters people and animals, and generates hydro-electricity.
• The downsides: heavy summer rain can cause severe flooding and landslides, and climate change is making the rains more erratic.
• A failed monsoon, with too little rain, makes it harder to grow food.
• A biome is a large community of vegetation and wildlife adapted to a specific climate. India has desert, savanna and forests.
• The Great Thar desert is one of the largest in the world, and part of it is in India.
• The Western Ghats' tropical forests are one of the most biodiverse places on Earth.
• The Sundarbans are a mangrove forest on the Bay of Bengal, shared by India and south-west Bangladesh.
• Known for the royal Bengal tiger and estuarine crocodile, the Sundarbans face climate change, overuse of resources and people–wildlife conflict.
• Three wildlife sanctuaries help conserve the Sundarbans' biodiversity.

The big picture

India doesn't have one climate. Its size and landscape give it several, and the monsoon is the big switch: a seasonal change in wind direction, caused by temperature and pressure differences between land and ocean, that brings about 70 per cent of the year's rain in just four months. That rain is vital, but too much or too little is dangerous. India's biomes, from the Thar desert to the Sundarbans mangroves, are just as varied.

⚠ Watch out

Mixing up the two monsoons. The south-west monsoon is the wet one: summer, June to September, about 70 per cent of the year's rain. The north-east monsoon is the dry one for most of India: winter, October to February.

Memory hook

Hot land, low pressure: the wind comes in and brings the rain. Cold land, high pressure: the wind goes out and the rain stays away.

Check yourself

Cover the page. Explain why winds blow in from the ocean in summer, why they reverse in winter, and what a failed summer monsoon does to growing food.