A chapter titled “Standard Study of Weather” for 7th-grade ICSE Geography Voyage would likely introduce fundamental concepts related to weather. It would probably cover:
- Definition of Weather: Explaining what weather is (day-to-day atmospheric conditions) and how it differs from climate (long-term patterns).
- Elements of Weather: Describing the key components used to measure and understand weather, such as temperature, pressure, wind, humidity, precipitation (rain, snow, hail, sleet), and sunshine.
- Instruments for Measuring Weather: Introducing the basic instruments used to measure these elements, like thermometers, barometers, anemometers, rain gauges, and hygrometers.
- Factors Affecting Weather: Discussing the main factors that influence local weather conditions, such as latitude, altitude, proximity to the sea, prevailing winds, and topography.
- Basic Weather Phenomena: Possibly a brief introduction to common weather events like clouds, fog, and simple precipitation types.
- Importance of Weather: Highlighting how weather affects our daily lives, agriculture, transportation, and more.
VALUES AND LIFE SKILLS
Many people leave their pets in parked cars. They think they will be gone for a few minutes, or it will be alright to leave a window open. The temperature inside a parked car can rise up to more than 50°C in a matter of few minutes, irrespective of it being a hot or a cloudy day.
What would be the right thing to do if you see a pet locked inside a car on a hot day ?
Ans:
The right thing to do is to immediately assess the situation, call emergency services if the pet is in distress, attempt to locate the owner, and, as a last resort and if legally permissible in your area, consider breaking a window to rescue the animal while simultaneously contacting authorities.
EXERCISES
A. Write true or false. Correct the false statements.
1. A rise in temperature causes more condensation while a fall in temperature results in evaporation.
Ans: False.
Correct : Arise in temperature causes more evaporation while a fall in temperature results in condensation.
2. ‘4 o’clock showers’ are caused by cyclonic rainfall.
Ans: False.
Correct : ‘4 o’clock showers’ are caused by convection currents.
3. Heavy rainfall occurs on the leeward or rain shadow side of a highland.
Ans: False.
Correct : Little rainfall occurs on the leeward or rain shadow side of a highland.
4. The direction of wind blowing on the surface of the earth is affected by the Coriolis force.
Ans: True.
5. Cyclones and anticyclones are examples of variable winds.
Ans: True.
B. Fill in the blanks.
1. The temperature of a place depends upon its ___________, ________, ___________, ocean currents, ________, _________ and _______ and ________.
Ans: latitude, altitude, distance from the sea, winds, cloud cover and slope and aspect.
2. Pressure difference causes horizontal movement of air called ______ and vertical movement of air called _______.
Ans: wind,current
3. Humidity refers to the amount of moisture or ________ present in the air.
Ans: water vapour
4. Planetary winds are also called permanent or __________ winds.
Ans: prevailing
5. The amount of cloud cover in the sky is expressed in __________________________.
Ans: discs (shaded in different proportions)
C. Answer the following questions in brief.
Question 1.
What are the elements that determine weather and climate?
Ans:
Weather and climate are shaped by the same components: how hot or cold it is (temperature), the weight of the air (pressure), how the air moves (wind), how much moisture is in the air (humidity), rain, snow, etc. (precipitation), how much sun there is (sunshine), and clouds. Weather is what’s happening with these right now, and climate is the typical pattern of these things over many years.
Question 2.
Name the factors that determine the temperature at a place.
Ans:
The temperature of a place is determined by several key factors:
- Latitude: How far north or south a place is from the Equator significantly impacts the amount of direct sunlight received, with areas closer to the Equator being warmer.
- Altitude: Higher elevations generally experience lower temperatures because the air is less dense and retains less heat.
- Distance from the Sea: Coastal areas have more moderate temperatures due to the slow heating and cooling of water, while inland areas have greater temperature extremes.
- Wind Patterns: Prevailing winds can carry air masses with different temperatures, influencing the temperature of a location.
- Land Features (Topography): Mountains can block air masses and influence temperature and precipitation, while the direction a slope faces affects solar radiation received.
- Vegetation: Plant cover can provide shade and release moisture, leading to slightly cooler temperatures.
- Soil Characteristics: Darker soils absorb more heat than lighter soils, affecting surface temperatures.
Question 3.
How do the following elements influence the weather of a place :
- temperature
- pressure?
Ans:
Temperature’s Influence: Temperature plays a crucial role in shaping a place’s weather by directly affecting air density and pressure. Warmer air, being less dense, exerts lower pressure and tends to rise, often leading to cloud formation and precipitation as it cools and condenses. Conversely, colder, denser air creates higher pressure and sinks, typically resulting in clear skies. Differences in temperature across regions generate pressure gradients, which drive the movement of air as wind. Furthermore, temperature dictates the atmosphere’s capacity to hold moisture (humidity), a key factor in cloud development and rainfall. Significant temperature contrasts can also provide the energy necessary for the formation of severe weather events.
Pressure’s Influence: In contrast, low-pressure systems typically bring unsettled weather, as rising air promotes cloud development and precipitation. Changes in pressure are also significant at weather fronts, the boundaries between air masses of different temperatures, influencing cloudiness, precipitation, and wind shifts. Rapid decreases in atmospheric pressure can be an indicator of approaching storms or unstable atmospheric conditions.
Question 4.
Name the various forms of precipitation.
Ans:
Liquid precipitation includes rain, characterized by water droplets larger than 0.5 mm, and drizzle, consisting of much finer droplets. Freezing rain and freezing drizzle occur when liquid precipitation falls through a layer of sub-freezing air near the ground, freezing upon impact with surfaces. Solid forms of precipitation encompass snow, which consists of aggregated ice crystals forming snowflakes, and smaller ice particles like snow grains and ice needles. Ice pellets (or sleet, in some definitions) are small, translucent ice spheres formed from refrozen raindrops or partially melted and refrozen snowflakes, while graupel are soft, rounded ice particles formed by supercooled water freezing onto snowflakes. Additionally, diamond dust refers to very small ice crystals that fall slowly in extremely cold conditions. Sometimes, precipitation can occur in mixed forms, such as a combination of rain and snow, or as slush, which is partially melted snow or ice.
Question 5.
How is cloud cover shown on a weather map? Give examples.
Ans:
Concise Representation:
Weather maps illustrate cloud cover through the shading of a central circle in a station model. An open circle denotes a clear sky. Partial shading signifies varying amounts of cloudiness, such as scattered or broken conditions. A solid circle indicates a completely overcast sky. When visibility is obstructed by phenomena like fog, a unique symbol, often a crossed circle, is employed.
Illustrative Examples:
- A forecast map for Pune displaying an unfilled circle suggests clear skies.
- A weather depiction for Mumbai showing a partially shaded circle indicates the presence of some clouds.
- A map of Nagpur featuring a solid circle signifies an overcast sky.
- A coastal weather station marked with a crossed circle might indicate fog is present or expected.
D. Answer the following questions in one or two paragraph’s.
Question 1.
How is weather different from climate?
Ans:
Weather refers to the atmospheric conditions at a specific place and time, which can change quickly. This includes factors such as the current temperature, humidity levels, wind speed and direction, any precipitation occurring (like rain, hail, or snow), and the amount of cloud cover. For example, the weather in Pune at this moment is warm, but conditions could shift significantly within the next few hours. Weather dictates immediate experiences and decisions based on the atmospheric environment.
It’s a statistical summary of the day-to-day weather, including average temperatures, typical rainfall amounts, and the frequency of different types of weather events. Pune’s climate, for instance, is characterized by prolonged periods of high temperatures and a distinct rainy season, based on historical weather data collected over many years. Climate influences long-term environmental factors and general expectations for seasonal changes in a location.
Question 2.
What is condensation? Explain these different forms of condensation: fog, mist, and dew.
Ans:
Condensation (Short): Water vapor turning into liquid due to cooling or excess moisture, forming clouds and ground moisture.
Fog (Short): Ground-level cloud of tiny water droplets, reducing visibility (under 1 km), forms when surface air cools to dew point and vapor condenses on particles. Types vary by cooling method.
Mist (Short): Less dense than fog, tiny water droplets, visibility 1-2 km, from slight cooling or humidity rise, needs particles.
Dew (Short): Water vapor condensing directly on cool surfaces (grass) at night/morning when surface cools air to dew point. Frost forms if surface is below freezing.
Question 3.
What do you understand by the term ‘4 o’clock showers’?
Ans:
The term “4 o’clock showers” describes a frequent weather pattern of afternoon convectional rainfall observed in equatorial regions around 4:00 PM local time. This phenomenon is driven by the following sequence: intense solar radiation throughout the day leads to significant surface heating, causing substantial evaporation and the ascent of warm, moisture-laden air (convection). With continued heating throughout the day, these clouds grow larger and become saturated, typically resulting in heavy but brief rainfall in the afternoon, often peaking around 4:00 PM. This daily cycle of heating and subsequent precipitation is characteristic of the hot and humid equatorial climates, such as those found in the Amazon and Congo basins, due to consistent high temperatures and abundant moisture supply.
Question 4.
What are planetary winds? Give a brief description of the Westerlies in the northern hemisphere.
Ans:
Planetary Winds (Short): Global winds blowing consistently due to uneven heating and Earth’s rotation (Coriolis effect). Main types: Trade Winds, Westerlies, Polar Easterlies.
Northern Hemisphere Westerlies (Short): Mid-latitude winds (30°-60°N) moving from subtropical high to subpolar low pressure. Coriolis effect deflects them, so they mainly blow southwest to northeast. They drive much of the mid-latitude weather, carrying moisture and moving storms. More variable than Southern Hemisphere Westerlies due to landmasses. Stronger in winter.
Question 5.
What are local winds? Give a few examples.
Ans:
Local Winds (Short): Winds blowing over small areas due to local temperature and pressure differences caused by geography (coastlines, mountains). Changeable and often daily/seasonal.
Examples (Short):
- Sea/Land Breeze: Daily coastal winds (sea to land in day, land to sea at night).
- Mountain/Valley Breeze: Daily mountain winds (valley to slope in day, slope to valley at night).
- Chinook: Warm, dry wind down Rockies.
- Mistral: Cold, dry wind in Rhône Valley.
- Loo: Hot, dry wind in North India/Pakistan.
E. With the help of your atlas,encylopaedias, and the Internet, find out about the climate of these places.
- Mumbai
- Delhi
- Kolkata
- London
- New York
- Sydney
Ans : Do it Yourself
F. In your notebook, draw neat, labelled, coloured sketches of the three different types of rainfall. Alongside each diagram, briefly describe in your own words, how each type of rainfall occurs.
Ans:
1. Convectional Rainfall
(Sketch):
^ Warm, Moist Air Rises
/ \
/ \
/ \
/_______\ -> Cooling & Condensation (Clouds form)
/_________\
/___________\ -> Further Condensation & Cloud Growth
____________
\ / Rain Clouds
\ /
V Heavy Rainfall
-----------------------
Warm Land Surface
Description:
Imagine the sun really heating up the land. This warm air becomes lighter and starts to rise, kind of like a hot air balloon. As this warm, moist air goes higher into the atmosphere, it gets cooler. This cooling causes the water vapor in the air to condense, turning into tiny water droplets. These droplets join together to form clouds. This type of rain is often heavy and can be accompanied by thunderstorms, especially in warmer regions and during the hotter parts of the day.
2. Orographic or Relief Rainfall
(Sketch):
Moist Air ----> /\ (Windward Side)
/ \ Ascending Air Cools & Condenses
/____\
/______\ -> Rain Clouds
/________\
/__________\ -> Heavy Rainfall
--------------------------
Mountain Barrier
\
\ (Leeward Side)
\ Descending Air Warms & Dries
\
------------> Dry Area (Rain Shadow)
Description:
When this moist air hits a mountain range or any significant land barrier, it has nowhere else to go but up. As the air is forced to rise along the slope of the mountain (the windward side), it starts to cool down. Just like in convectional rainfall, this cooling leads to condensation, forming clouds. As more moist air keeps getting pushed up and cooling, these clouds become heavy with water droplets, and it starts to rain – this is orographic rainfall. The side of the mountain facing the wind and getting the rain is called the windward side. After the air has dropped most of its moisture as rain, it moves over the top of the mountain and down the other side (the leeward side). As this air descends, it gets warmer and can hold more moisture, so this side of the mountain often receives very little rainfall, creating a dry area known as a rain shadow.
3. Cyclonic or Frontal Rainfall
(Sketch):
Warm Air Mass ---->
/ / / / / / / /
/ / / / / / / /
/_____________/
Cold Air Mass <----
-----------------
^
| Warmer, Lighter Air Rises Over Cold, Denser Air
| Cooling & Condensation (Clouds form along the front)
|
V Rain Clouds
|
V Moderate to Heavy Rainfall
-----------------------
Ground Surface
Description:
Imagine a situation where a large mass of warm air meets a large mass of cold air. The boundary where these two air masses meet is called a front. As the warm, moist air is forced to rise along this frontal surface, it starts to cool down. This cooling again leads to condensation, forming clouds along the front. These clouds can be quite extensive and often bring cyclonic or frontal rainfall. The intensity and duration of this rain can vary depending on the type of front (warm front or cold front) and the amount of moisture in the air. This type of rainfall is often associated with larger weather systems and can cover wide areas.
Question 2.
Which side of the mountain is likely to have houses and be covered with trees ?
Ans:
The side of the mountain that is likely to have houses and be covered with trees is generally the windward side.
- Orographic Rainfall: Mountains often cause a phenomenon called orographic or relief rainfall. When moist air is forced to rise over a mountain range, it cools and condenses, leading to significant precipitation on the side facing the wind (the windward side).
- Lush Vegetation: The abundant rainfall on the windward side supports the growth of trees and other vegetation, leading to a denser forest cover.
- Habitability: The availability of water and the generally more favorable conditions for agriculture and human needs often make the windward side more suitable for settlements and houses.
