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Class 9 Atmosphere and Climate: cheat sheet
CBSE Social Science. 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
| Layers, from the ground | troposphere → stratosphere → mesosphere → thermosphere → exosphere |
| Climate | the average weather over 30 years or more |
| Sea and land breeze | sea to land by day; land to sea at night |
| IMD seasons | winter, summer (pre-monsoon), monsoon, post-monsoon |
| Monsoon | from the Arabic “mausim”, season |
| Six ritus | Vasanta, Grishma, Varsha, Sharad, Hemanta, Shishira |
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
What is a wind called if it blows from (a) the north (b) the east?
Working: winds are named after where they come from
Answer: (a) a northerly (b) an easterly
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