NCERT Class 7 Social Science Exploring Society India and Beyond Part 1 Chapter 02 Understanding the Weather PDF Download

Chapter 2: Understanding the Weather

[Figure 2.1: Weather in different regions -, See in your textbook]

Weather and its Elements

You wake up one winter morning and shiver. You reach for thick clothes to keep yourself warm. In the summer, you choose clothes that keep you cool and comfortable. You are responding to your body's signals; your body is sensing the weather.

What is weather?

Weather is a state of the Earth's atmosphere at a particular time and place. But what is an atmosphere? In simple terms, it is the layer of gases that surround some planets - in the case of our Earth, we call these gases 'air'. The Earth's atmosphere may be compared to a cake with several layers. The layer closest to the surface of the Earth is called the 'troposphere', and that is where all land-based plants and animals (including humans!) live and breathe. It is also where almost all weather phenomena, which we will explore in this chapter, take place. The troposphere extends to a height of 6 to 18 kilometres from the ground; it is less thick at the poles (where the cold air contracts) and thicker in the tropical zone (where the warmer air expands). You will study more about the other layers in your Science classes.

We use many words to describe the weather - hot, cold, rainy, cloudy, humid, snowy, windy, and so on. They describe the different ways in which we experience the elements of weather.

[Figure 2.2: Layers of Earth's atmosphere -, See in your textbook]

Let's Explore

What are some of the words in your local language that you use to describe the weather? Hot, cold, warm, chilly, crisp, pleasant, and so on, are commonly used terms in English.

The elements of weather are:

• Temperature: How hot or cold the atmosphere is.
• Precipitation: Any form of water, such as rain, snow, sleet or hail, that falls from the sky.
• Atmospheric Pressure: The weight of the air above us, felt on the Earth's surface.
• Wind: The movement of air, including its speed and direction.
• Humidity: The amount of water vapour in the air.

Think About It

Let us imagine that Krishnan from Chennai is speaking with Amir in Kashmir. Krishnan tells Amir that it has become chilly in Chennai after it rained the previous night. Amir asks him how cold it is. How will Krishnan explain to Amir how cold it is? After all, what is cold for Krishnan may be quite pleasant for Amir!

As you can see, it would be difficult for Krishnan to convey his sense of chillness to Amir unless there is a commonly agreed way to measure the temperature. It is the same with other elements of the weather. In this chapter, we will learn how we measure the weather using common standards.

Teacher's Note

Weather is described using five main elements, and each one measures something different. Temperature tells you how hot or cold it is, while humidity tells you how much moisture is in the air - do not mix these up. When you read a weather report, check which element is being measured before you use the number to make a decision, like what to wear or what activity to plan.

Let's Explore

What do you think could be some other reasons to measure the weather more precisely? (Hint: Think how knowing the weather a few hours or a few days in advance would help you plan some activities.)

From early times, humans have closely observed Nature and learnt to read her signals to forecast the weather. Observing birds flying low, ants carrying eggs, squirrels gathering nuts, frogs croaking loudly, or even the opening and closing of pine cones, provided valuable information about coming rain or storms. This knowledge has been passed down from generation to generation. Even today, in many parts of India, people use traditional ways to predict the weather, especially the arrival of the monsoon.

Teacher's Note

Long before weather instruments were invented, people predicted rain and storms by watching nature carefully - birds, ants, frogs, and even plants gave them clues. This shows that careful observation is the foundation of all measurement and prediction. Today we use scientific instruments, but the same principle of observing patterns and making predictions still applies.

Key Points

• Weather is the state of the atmosphere at a particular time and place, and most weather happens in the troposphere, the lowest layer of air around Earth.
• The five main elements of weather are temperature, precipitation, atmospheric pressure, wind, and humidity, and each one needs to be measured using common standards.
• Different places have different ideas about what is hot or cold, so people created standard ways to measure temperature so everyone can understand the weather in the same way.
• Humans have always watched nature - birds, insects, animals, and plants - to predict rain and storms, and this traditional knowledge is still used in many parts of India today.

This is a preview of the first 3 pages. To get the complete chapter, click below.