Selina Concise Solutions for ICSE Class 7 Geography Chapter 6 Recording of Weather

Discuss

Question: How are dew drops beneficial for plants ?
Answer:
In the early morning dew surrounds the leaves of plant with moisture and plant does not close its stomata.
Dew provides a natural source of water directly to the leaf surface before the sun gets too hot. This extra hydration helps plants stay healthy during dry periods.
Teacher's Tip: Think of dew as the plant's "morning drink" that refreshes them before the day begins.
Exam Tip: Always mention "stomata" when talking about dew and plants for better marks.

EXERCISES

A. Answer the following questions in brief

Question 1: What is relative humidity? How does it differ from absolute humidity ?
Answer:
Relative humidity is the ratio of the actual amount of water vapour present in the air and the total amount the air can hold at a given temperature. It is expressed in percentage. While absolute humidity is measured in grams per cubic metre.
Relative humidity tells us how "full" the air is with water compared to its maximum capacity. Absolute humidity simply measures the total weight of water in a specific volume of air.
Teacher's Tip: Remember: Relative = percentage (%), Absolute = weight (g/m³).
Exam Tip: Differentiate clearly by mentioning the units of measurement for both.

Question 2: What does a large difference between the temperatures of a dry bulb thermometer and a wet bulb thermometer of a hygrometer indicate?
Answer:
A large difference between the readings of the two thermometers means low relative humidity and a small difference between them means high relative humidity.
A large difference happens because evaporation from the wet bulb cools it down much faster when the air is dry. When the air is already moist, very little evaporation occurs, so the temperatures stay close together.
Teacher's Tip: Big Gap = Dry Air; Small Gap = Moist Air.
Exam Tip: Use the term "evaporation" to explain why the wet bulb temperature drops.

Question 3: Differentiate between precipitation and condensation. Give one example of each.
Answer:
Condensation - Dew is a form of condensation. Condensation is the process by which water vapour in the air gets converted into tiny droplets of water or ice. Dew forms in winters when the temperature is very low but not below 0°C. Moist air comes in contact with the cold surfaces near the ground. The water vapour in the air changes to water and we see it as dew drops on grass or on plants. Dew drops are beneficial for plants.
Precipitation - Precipitation is the falling of atmospheric moisture as a result of condensation. It has many forms such as rainfall, snowfall, and hail.
Condensation is the "changing" of state from gas to liquid, while precipitation is the "falling" of that liquid to the ground. You can see condensation on the outside of a cold glass of water.
Teacher's Tip: Condensation is "making" water; Precipitation is "dropping" water.
Exam Tip: Always include examples like rainfall or snow to complete your differentiation.

Question 4: What are nimbus clouds?
Answer:
Nimbus are real rain clouds-thick, dark and black and spread out in layers. They cause continuous rain or snow.
These clouds look heavy and dark because they are densely packed with water droplets. They are often associated with long periods of steady precipitation rather than quick storms.
Teacher's Tip: "Nimbus" is Latin for "rain storm" - think of dark, heavy rain!
Exam Tip: Describe their physical appearance (thick and dark) as well as the type of weather they bring.

Question 5: What is the Beaufort scale?
Answer:
Beaufort scale is the scale that is used to estimate wind speed. The scale is based on the effect of the wind at different speeds.
It ranges from 0 (calm) to 12 (hurricane force) based on visual observations like smoke or moving tree branches. It was originally created for sailors but is now used by everyone to describe wind conditions.
Teacher's Tip: Look at tree leaves moving; if they just rustle, it is a low number on the Beaufort scale.
Exam Tip: Mention that it is used for "estimating" wind speed based on "visual effects."

B. Answer the following questions in one or two paragraphs

Question 1: What is a hygrometer ?
Answer:
The instrument used for measuring relative humidity is called hygrometer. The hygrometer consists of wet and dry bulb thermometer. The dry bulb thermometer is an ordinary thermometer while the wet bulb thermometer is kept wet by a wick that dips into a container of distilled water. The wet bulb thermometer shows the lower temperature than the actual temperature as evaporation from the moist wick has a cooling effect. A larger difference between readings of two thermometers means low relative humidity and small difference means high relative humidity.
By comparing the two temperatures, we can determine how much moisture is in the atmosphere. The cooling effect on the wet bulb is a direct result of how fast water can evaporate into the surrounding air.
Teacher's Tip: Think of the "Wet bulb" as a thermometer wearing a wet sweater!
Exam Tip: Draw a simple diagram if the question asks for a detailed description.

Question 2: Describe the various types of clouds.
Answer:
The four types of clouds are :
(a) Cirrus clouds - These are feathery, fibrous clouds which form at very high levels of 5 to 10 km. They consist of tiny crystals of ice and look like wisps of cotton floating in the sky.
(b) Cumulus clouds - These are cauliflower-shaped clouds that have great vertical height and a flat base; they cause rainfall with lightning and thunder, and are usually white or grey in colour.
(c) Stratus clouds - These are sheet-like clouds that spread out over the whole sky. They usually form at low levels, less than 2 km. They are uniformly grey and dull.
(d) Nimbus clouds - These are the real rain clouds - thick, dark and black, and spread out in layers. They cause continuous rain or snow.
Clouds are classified based on their height and physical appearance in the atmosphere. Knowing these types helps us predict what kind of weather is coming our way.
Teacher's Tip: High = Cirrus, Fluffy = Cumulus, Sheets = Stratus, Rain = Nimbus.
Exam Tip: Mention the altitude (height) for each cloud type to score full marks.

Question 3: What is wind? What precautions must be taken while placing a wind vane?
Answer:
Wind is air in motion. A wind vane indicates the direction of the wind and consists of a rotating arm pivoted on a vertical rod. The arrow of the wind vane always points in the direction from which the wind blows and the wind is named accordingly. For example, if the pointer is pointing to the East, the wind is blowing from East to West and, therefore, this wind is called an easterly wind. Wind vanes are usually placed away from obstacles such as high buildings, trees, etc.
Wind occurs due to differences in air pressure caused by the uneven heating of the Earth's surface. It is important to place a wind vane in an open area so that buildings or trees don't block or swirl the air currents.
Teacher's Tip: Wind direction is "where it comes from," not "where it's going."
Exam Tip: Be sure to explain why obstacles like buildings should be avoided in placement.

Question 4: What are isohyets and isotherms ?
Answer:
Isohytes : A weather map, which shows, by the help of lines, the amount of rainfall a place receives. Each of these lines is made by joining points that show the same amount of rainfall received in a given period. These lines are known as isohyets.
Isotherm : On the map, places experiencing the same temperature at a given time are connected with a line. This line is known as an isotherm. Each of these points on the line reflects one temperature reading, or an average of several readings, over a period of time.
These lines help geographers and weather forecasters see patterns across large areas easily. Just like contour lines show height, these show climate and weather data visually.
Teacher's Tip: "Iso" means same. "Therm" = Heat; "Hyet" = Rain.
Exam Tip: Clearly state that "Iso" means equal or same in your definitions.

Question 5: What is a weather report ? How is weather forecast made? Why is weather forecast necessary ?
Answer:
When the weather conditions of the previous day are published, it is called a weather report. Weather forecasting is the application of science and technology to predict the state of the atmosphere for a given location. Nowadays it is made with the help of data gathered from weather satellites and radar systems. Forecasts help to plan what to wear, when to travel or which products to stock in super markets. It’s specially important for farmers, builders, sailors or anyone else who works out doors.
Forecasting uses complex math and patterns of current air movement to guess the future weather. It saves lives by warning people about dangerous storms before they arrive.
Teacher's Tip: Report = Past; Forecast = Future.
Exam Tip: List at least two groups of people (like farmers or sailors) who rely on forecasts.

C. For a week, gather information on the weather conditions of your city using simple instruments or from weather reports published in newspapers. Present this information in a table. One has been done for you here. My observation of the weather at for a week.
Answer:
Day: Tuesday, Date: 1.5.2017, Morning: Sunny, clear sky, warm, no rainfall, Evening: Cloudy, cold, slight drizzle
Day: Tuesday, Date: 8.5.2017, Morning: Mostly Sunny & hot, Evening: Clear & humid
Day: Wednesday, Date: 9.5.2017, Morning: A thunderstorm in spots, Evening: Cloudy, cold, slight drizzle
Day: Thursday, Date: 10.5.2017, Morning: More sun than clouds, Evening: Clear & humid
Day: Friday, Date: 11.5.2017, Morning: More sun than clouds, Evening: Clear & humid
Day: Saturday, Date: 12.5.2017, Morning: A few showers, Partly cloudy, Evening: Cloudy, cold, slight drizzle
Day: Sunday, Date: 13.5.2017, Morning: A thunderstorm in spots, Evening: Cloudy, cold, slight drizzle
Day: Monday, Date: 14.5.2017, Morning: Mostly Sunny & hot, Evening: Clear & humid
Keeping a weather diary is the first step toward becoming a meteorologist. It helps you notice how conditions in the morning often dictate how the evening will turn out.
Teacher's Tip: Look out your window at the same time every day to get consistent observations.
Exam Tip: If asked to record weather, use clear columns for Morning and Evening.

D. This could be a classroom activity. If your school laboratory has an anemometer, use it to record your city’s wind speed for a week. Use the Beaufort Scale to find out the character of wind during these days. Record your observations carefully in your notebook. You could even draw small neat sketches to show the effect of the wind.
Answer:
Do it Yourself
An anemometer measures the speed of wind, which is crucial for aviation and sailing. The Beaufort Scale provides a handy way to check these speeds even without fancy equipment.
Teacher's Tip: You can make a simple anemometer at home using paper cups and straws!
Exam Tip: Mention that anemometers measure "speed" while wind vanes measure "direction."

E. From the weather report published in your local newspaper, record the time of sunrise and sunset for a month in your notebook, as shown on the next page : My observation of the time of sunrise and sunset for the month of ______ 20, ______
Answer:
10 June 2017, Sunrise: 5.24 a.m., Sunset: 5.51 p.m., Day Length: 12 hours and 27 minutes
11 June 2017, Sunrise: 5.25 a.m., Sunset: 5.55 p.m., Day Length: 12 hours and 30 minutes
12 June 2017, Sunrise: 5.35 a.m., Sunset: 5.57 p.m., Day Length: 12 hours and 22 minutes
13 June 2017, Sunrise: 5.36 a.m., Sunset: 5.54 p.m., Day Length: 12 hours and 18 minutes
14 June 2017, Sunrise: 5.25 a.m., Sunset: 5.50 p.m., Day Length: 12 hours and 25 minutes
15 June 2017, Sunrise: 5.19 a.m., Sunset: 5.58 p.m., Day Length: 12 hours and 39 minutes
16 June 2017, Sunrise: 5.35 a.m., Sunset: 5.58 p.m., Day Length: 12 hours and 23 minutes
17 June 2017, Sunrise: 5.45 a.m., Sunset: 6.10 p.m., Day Length: 12 hours and 25 minutes
18 June 2017, Sunrise: 5.36 a.m., Sunset: 6.02 p.m., Day Length: 12 hours and 26 minutes
19 June 2017, Sunrise: 5.37 a.m., Sunset: 5.58 p.m., Day Length: 12 hours and 21 minutes
20 June 2017, Sunrise: 5.24 a.m., Sunset: 5.59 p.m., Day Length: 12 hours and 35 minutes
21 June 2017, Sunrise: 5.25 a.m., Sunset: 5.57 p.m., Day Length: 12 hours and 32 minutes
22 June 2017, Sunrise: 5.18 a.m., Sunset: 5.52 p.m., Day Length: 12 hours and 34 minutes
23 June 2017, Sunrise: 5.24 a.m., Sunset: 5.56 p.m., Day Length: 12 hours and 32 minutes
24 June 2017, Sunrise: 5.23 a.m., Sunset: 5.53 p.m., Day Length: 12 hours and 30 minutes
25 June 2017, Sunrise: 5.31 a.m., Sunset: 5.49 p.m., Day Length: 12 hours and 18 minutes
26 June 2017, Sunrise: 5.37 a.m., Sunset: 5.59 p.m., Day Length: 12 hours and 22 minutes
27 June 2017, Sunrise: 5.39 a.m., Sunset: 6.05 p.m., Day Length: 12 hours and 26 minutes
28 June 2017, Sunrise: 5.25 a.m., Sunset: 6.07 p.m., Day Length: 12 hours and 42 minutes
29 June 2017, Sunrise: 5.29 a.m., Sunset: 6.03 p.m., Day Length: 12 hours and 34 minutes
30 June 2017, Sunrise: 5.30 a.m., Sunset: 6.08 p.m., Day Length: 12 hours and 38 minutes
1 July 2017, Sunrise: 5.27 a.m., Sunset: 6.06 p.m., Day Length: 12 hours and 39 minutes
2 July 2017, Sunrise: 5.19 a.m., Sunset: 6.01 p.m., Day Length: 12 hours and 42 minutes
3 July 2017, Sunrise: 5.17 a.m., Sunset: 6.02 p.m., Day Length: 12 hours and 45 minutes
4 July 2017, Sunrise: 5.27 a.m., Sunset: 6.12 p.m., Day Length: 12 hours and 45 minutes
5 July 2017, Sunrise: 5.39 a.m., Sunset: 6.09 p.m., Day Length: 12 hours and 30 minutes
6 July 2017, Sunrise: 5.45 a.m., Sunset: 6.19 p.m., Day Length: 12 hours and 34 minutes
7 July 2017, Sunrise: 5.48 a.m., Sunset: 6.22 p.m., Day Length: 12 hours and 34 minutes
8 July 2017, Sunrise: 5.51 a.m., Sunset: 6.27 p.m., Day Length: 12 hours and 36 minutes
9 July 2017, Sunrise: 5.53 a.m., Sunset: 6.26 p.m., Day Length: 12 hours and 33 minutes
Notice how the length of the day changes slightly each day as we move through the seasons. This data proves that the Earth's tilt affects how much sunlight different places receive.
Teacher's Tip: The longest day of the year occurs in June in the Northern Hemisphere.
Exam Tip: To calculate the length of day, subtract the sunrise time from the sunset time.

F. Picture Study

Question 1: Identify the four types of clouds shown in the photographs.
Answer:
1.(a) Cirrus clouds
(b) Cumulus clouds
(c) Stratus clouds
(d) Nimbus clouds
Identifying clouds by their shapes is a useful skill for predicting upcoming weather. For example, seeing wispy cirrus clouds high up often means a change in weather is 24 hours away.
Teacher's Tip: Match the name to the look: cauliflower = cumulus!
Exam Tip: Be careful with identifying the "dark" cloud as Nimbus to get full marks.

Question 2: Which of these causes heavy rainfall?
Answer:
Nimbus clouds causes heavy rainfalls.
Nimbus clouds are specifically designated for rain and are usually low-hanging and thick. They can cover the entire sky and bring rain that lasts for many hours.
Teacher's Tip: Remember: Nimbus = Rain cloud.
Exam Tip: Use the word "heavy" or "continuous" as specified in the cloud description.