Atmosphere and Climate

The gases and layers of the atmosphere, weather and climate, pressure and winds, India’s seasons and monsoons, and climate change.

Key ideas

• Nitrogen is the most plentiful gas in the air, and almost all weather happens in the lowest layer, the troposphere.
• The ozone layer is in the stratosphere, meteors burn up in the mesosphere and auroras glow in the thermosphere.
• Weather is the state of the air from day to day; climate is the average over a large area for 30 years or more.
• Temperature, precipitation, humidity, wind and air pressure are the elements of both weather and climate.
• Wind blows from high pressure to low pressure and is named after the direction it comes from.
• The southwest monsoon (June–September), caused by unequal heating of land and sea, brings most of India’s rain; the northeast monsoon rains on the Tamil Nadu coast after crossing the Bay of Bengal.
• Insolation is strongest near the Equator, so places get colder as latitude increases.
• Climate change comes mainly from greenhouse gases added by human activity; saving energy and planting trees cut our carbon footprint.

Remember

Watch out

• Naming a wind after where it is going: a westerly blows from the west.
• Using weather and climate as the same thing.
• Putting the ozone layer in the troposphere: it is in the stratosphere.

Worked example