Measuring Temperature and Rainfall

Class 7 Social Science · Chapter 2: Understanding the Weather · NCERT Exploring Society: India and Beyond section 2.2

Learn

Thermometers measure temperature in degrees Celsius (°C) or Fahrenheit (°F): 15 °C is the same as 59 °F. Some show the current (ambient) temperature; others record the day's maximum and minimum. Digital thermometers are more precise and store more data. Even without one, you notice clues: coconut oil turns solid and curd sets slowly in cold weather.

From these readings we calculate useful statistics. The range of temperature is maximum − minimum; the mean daily temperature is (maximum + minimum) ÷ 2. Meher's town recorded 32 °C and 18 °C on Monday: range 14 °C, mean 25 °C. The India Meteorological Department (IMD), set up in 1875, has the motto "ādityāt jāyate vṛṣṭiḥ": from the sun arises rain.

range = max − min; mean = (max + min) ÷ 2

Rainfall is measured with a rain gauge: a funnel leads rain into a cylinder with a scale. If the water stands 5 mm deep, the place got 5 mm of rainfall. Snow is melted before measuring. Neel's class builds one from a bottle and places it on a raised platform in open ground, away from walls and trees, reading it at the same time every day.

Explore: where should the rain gauge go?

1. Sort each spot.

Remember

• Thermometers measure temperature (°C/°F); range = max − min, mean = (max + min) ÷ 2.
• A rain gauge measures rainfall in mm; the IMD was set up in 1875.

Quick check

Max 31 °C and min 17 °C. What is the mean daily temperature?

1. 24 °C
2. 14 °C
3. 48 °C
4. 31 °C

Think about it

Why should a rain gauge not be kept under a tree or near a wall?

Practice

Practise with fresh questions at three levels (easy, medium, hard), some answered hands-on, with hints and worked answers. Get 4 of your last 5 right to finish the topic.