Class 11 Geography: Climate
A. Multiple Choice Questions (MCQs) - 1 Mark Each (Total: 15 Marks)
Which of the following is NOT an element of weather and climate?
a) Temperature
b) Pressure
c) Topography
d) Precipitation
Answer: c) Topography
Hint: Elements are measurable atmospheric conditions, while topography is a factor influencing them.
Rationale: Temperature, pressure, wind, humidity, and precipitation are elements of weather and climate. Topography (relief) is a control or factor that influences climate, not an element itself.
The lowest layer of the atmosphere where almost all weather phenomena occur is the:
a) Stratosphere
b) Mesosphere
c) Troposphere
d) Thermosphere
Answer: c) Troposphere
Hint: This is the layer closest to the Earth's surface.
Rationale: The troposphere is the lowest atmospheric layer, extending up to about 8-18 km, where most clouds, rain, snow, and other weather phenomena are observed.
The process by which incoming solar radiation is absorbed by the Earth's surface and then radiated back as longwave radiation, trapping heat in the atmosphere, is known as the:
a) Ozone depletion
b) Coriolis effect
c) Greenhouse effect
d) Albedo effect
Answer: c) Greenhouse effect
Hint: This process is crucial for maintaining Earth's warmth.
Rationale: The greenhouse effect is the natural process where certain gases in Earth's atmosphere trap heat, warming the planet. Ozone depletion is about the ozone layer, Coriolis effect is about deflection of moving objects, and albedo is reflectivity.
Which of the following is a planetary wind system blowing from the subtropical high-pressure belts to the subpolar low-pressure belts?
a) Trade Winds
b) Westerlies
c) Polar Easterlies
d) Monsoon Winds
Answer: b) Westerlies
Hint: These winds are dominant in the middle latitudes.
Rationale: The Westerlies blow from the subtropical high-pressure belts towards the subpolar low-pressure belts in both hemispheres (southwesterly in the Northern Hemisphere and northwesterly in the Southern Hemisphere). Trade Winds are tropical, Polar Easterlies are polar, and Monsoons are periodic.
The amount of moisture present in the atmosphere is called:
a) Precipitation
b) Condensation
c) Humidity
d) Saturation
Answer: c) Humidity
Hint: This term directly refers to water vapor content.
Rationale: Humidity is the general term for the amount of water vapor in the atmosphere. Precipitation is water falling from the atmosphere, condensation is the change of state from vapor to liquid, and saturation is the point where air holds maximum moisture.
Which type of rainfall is associated with the ascent of warm, moist air along a mountain barrier?
a) Convectional rainfall
b) Orographic rainfall
c) Cyclonic rainfall
d) Frontal rainfall
Answer: b) Orographic rainfall
Hint: 'Oro' relates to mountains.
Rationale: Orographic rainfall occurs when moist air is forced to rise over a mountain range (orographic barrier), cools, condenses, and precipitates. Convectional rainfall results from localized heating, and cyclonic/frontal rainfall is associated with cyclones/fronts.
The temperature at which a parcel of air becomes saturated and condensation begins is called the:
a) Freezing point
b) Boiling point
c) Dew Point
d) Absolute temperature
Answer: c) Dew Point
Hint: This is the critical temperature for moisture to turn into liquid.
Rationale: The dew point is the temperature to which air must be cooled at constant pressure for water vapor to condense into liquid water (dew).
The ITCZ (Inter-Tropical Convergent Zone) is a zone of:
a) High pressure and diverging winds
b) Low pressure and converging winds
c) High pressure and converging winds
d) Low pressure and diverging winds
Answer: b) Low pressure and converging winds
Hint: This zone is characterized by rising air and the meeting of trade winds.
Rationale: The ITCZ is a band of low pressure that encircles the Earth near the Equator, where the northeast and southeast trade winds converge, causing air to rise and creating a zone of frequent thunderstorms and heavy rainfall.
Which of the following factors causes a decrease in temperature with increasing altitude?
a) Ocean currents
b) Coriolis effect
c) Normal Lapse Rate
d) Land and sea breezes
Answer: c) Normal Lapse Rate
Hint: This is the standard rate of temperature change with height in the troposphere.
Rationale: The normal lapse rate describes the decrease in temperature with increasing altitude in the troposphere, typically about 6.5°C per 1000 meters, primarily due to the decreasing density and heat-absorbing capacity of air at higher altitudes.
Köppen's classification system primarily uses which two elements of climate to define climate types?
a) Pressure and Wind
b) Humidity and Clouds
c) Temperature and Precipitation
d) Latitude and Altitude
Answer: c) Temperature and Precipitation
Hint: These are the most fundamental climatic characteristics.
Rationale: The Köppen climate classification system is a widely used system that categorizes climates based on annual and monthly averages of temperature and precipitation, and the seasonality of precipitation.
The sudden and violent rise in the water level of a river or coastal area due to a tropical cyclone is called a:
a) Tsunami
b) Tidal wave
c) Storm Surge
d) Seiche
Answer: c) Storm Surge
Hint: This is a key destructive element of cyclones.
Rationale: A storm surge is an abnormal rise in sea level generated by a storm, over and above the predicted astronomical tides. It is primarily caused by the strong winds of a cyclone pushing water towards the shore and the low atmospheric pressure of the storm.
Mediterranean climate is characterized by:
a) Hot, wet summers and mild, dry winters
b) Hot, dry summers and mild, wet winters
c) Cold, dry winters and hot, wet summers
d) Uniformly high temperature and high rainfall throughout the year
Answer: b) Hot, dry summers and mild, wet winters
Hint: Think about the climate of regions like California or parts of Europe.
Rationale: Mediterranean climate (Cs in Köppen's system) is distinctive for its hot, dry summers and mild, rainy winters. This is influenced by the poleward shift of subtropical high-pressure belts in summer and the influence of westerlies in winter.
Which layer of the atmosphere is primarily responsible for absorbing harmful ultraviolet (UV) radiation from the Sun?
a) Troposphere
b) Stratosphere
c) Mesosphere
d) Thermosphere
Answer: b) Stratosphere
Hint: This layer contains the ozone layer.
Rationale: The stratosphere contains the ozone layer, which is crucial for absorbing most of the Sun's harmful ultraviolet (UV) radiation, protecting life on Earth.
The flow of air from an area of high pressure to an area of low pressure is called:
a) Convection
b) Advection
c) Wind
d) Subsidence
Answer: c) Wind
Hint: This is the fundamental definition of horizontal air movement.
Rationale: Wind is defined as the horizontal movement of air from an area of higher atmospheric pressure to an area of lower atmospheric pressure. Convection is vertical air movement, and advection is horizontal heat transfer.
What is the primary cause of the deflection of winds and ocean currents in the Northern Hemisphere to the right and in the Southern Hemisphere to the left?
a) Gravitational force
b) Centrifugal force
c) Coriolis force
d) Magnetic force
Answer: c) Coriolis force
Hint: This apparent force is due to Earth's rotation.
Rationale: The Coriolis force, an apparent force resulting from the Earth's rotation, deflects moving objects (including winds and ocean currents) to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
B. Short Answer Questions (2-3 Marks Each) - (Total: 20-30 Marks)
Differentiate between weather and climate.
Answer: Weather refers to the day-to-day atmospheric conditions at a particular place and time (e.g., today's temperature, rain, wind). Climate refers to the long-term average weather pattern for a particular region, usually calculated over a period of 30 years or more, including its variations and extremes.
Explain the concept of 'Temperature Inversion'.
Answer: Temperature inversion is an atmospheric condition where a layer of cool air is trapped beneath a layer of warmer air, essentially reversing the normal temperature decrease with altitude (normal lapse rate). This can happen near the ground due to rapid cooling of the surface at night (radiation inversion) or when warm air overruns cold air (frontal inversion). Inversions can trap pollutants near the surface, leading to smog.
List and briefly explain any two controls of climate.
Answer: Any two of the following:
Latitude: Affects the angle of incidence of sun's rays. Places near the equator receive direct rays and are hotter, while those near the poles receive oblique rays and are colder.
Altitude: Temperature decreases with increasing height (Normal Lapse Rate). Higher places are cooler than lower places at the same latitude.
Distance from the Sea (Continentality): Land heats up and cools down faster than water. Coastal areas experience moderate climates with smaller temperature ranges, while interior continental areas experience extreme (continental) climates with large annual temperature ranges.
Ocean Currents: Warm ocean currents raise the temperature of coastal areas they flow past, while cold currents lower it, also influencing precipitation patterns.
Wind Systems: Prevailing winds carry the characteristics of their source region (e.g., dry from land, moist from sea), influencing temperature and precipitation.
Relief (Topography): Mountain barriers can block winds or cause orographic rainfall on their windward side and create rain shadows on their leeward side.
Briefly explain the formation of Convectional Rainfall.
Answer: Convectional rainfall occurs when the ground surface is intensely heated by the sun, causing the air above it to warm up, expand, and become lighter. This warm, moist air rises rapidly in convection currents. As it rises, it cools, condenses to form cumulonimbus clouds, and eventually leads to heavy rainfall, often accompanied by thunder and lightning. This type of rainfall is common in equatorial regions and during hot summer afternoons in continental areas.
What are 'Jet Streams'? Where are they located?
Answer: Jet streams are narrow bands of strong, fast-moving, meandering air currents located in the upper troposphere, typically between 7 and 16 km altitude. They generally flow from west to east. There are two main types: the polar jet stream and the subtropical jet stream. They play a significant role in influencing global weather patterns, affecting the movement of air masses, cyclones, and anticyclones.
How does 'Relative Humidity' differ from 'Absolute Humidity'?
Answer: Absolute humidity is the actual amount of water vapor present in a given volume of air, usually expressed in grams of water vapor per cubic meter of air (g/m$^3$). Relative humidity is the ratio of the actual amount of water vapor present in the air to the maximum amount of water vapor the air can hold at that specific temperature and pressure, expressed as a percentage. It indicates how close the air is to saturation.
Explain the 'Monsoon' as a periodic wind system.
Answer: Monsoon refers to a seasonal reversal of wind direction that is accompanied by corresponding changes in precipitation. It is a large-scale land and sea breeze system. During summer, land heats up faster than the sea, creating low pressure over land and high pressure over the sea, leading to moist winds blowing from sea to land (summer monsoon, bringing rain). In winter, the pattern reverses, with high pressure over land and low over sea, causing dry winds to blow from land to sea (winter monsoon).
Name the four main layers of the atmosphere in order from the Earth's surface upwards.
Answer: The four main layers of the atmosphere from Earth's surface upwards are:
Troposphere
Stratosphere
Mesosphere
Thermosphere (or Ionosphere within it)
What is a 'Rain Shadow Area'? Give an example.
Answer: A rain shadow area is a dry region on the leeward (downwind) side of a mountain range. It occurs when moist air is forced to rise over the windward side of the mountains, cools, condenses, and releases its moisture as orographic rainfall. By the time the air descends on the leeward side, it has lost most of its moisture, warms up, and becomes dry, creating arid or semi-arid conditions. Example: The eastern side of the Western Ghats in India, or the Great Basin in the USA (east of the Sierra Nevada mountains).
What is the main difference between a Tropical Cyclone and a Temperate Cyclone?
Answer: Tropical Cyclones (e.g., hurricanes, typhoons) form over warm tropical oceans, are characterized by intense low pressure, a compact size, high wind speeds, heavy rainfall, and no fronts. They derive energy from latent heat of condensation. Temperate Cyclones (e.g., mid-latitude depressions) form in the middle latitudes along fronts (where warm and cold air masses meet), are larger in size, less destructive wind speeds, and have distinct warm and cold fronts associated with different types of precipitation. They derive energy from the temperature contrast between air masses.
C. Long Answer Questions (5-6 Marks Each)
Explain the major factors (controls) that influence the climate of a place. Elaborate with suitable examples.
Answer:
The climate of any place on Earth is determined by a complex interplay of several geographical factors, often referred to as 'controls of climate'. These factors explain the vast diversity of climatic conditions across the globe.
Latitude: This is the most fundamental control. The angle at which the sun's rays strike the Earth's surface varies with latitude. Near the equator (low latitudes), sun's rays are more direct and concentrated, leading to higher temperatures. Towards the poles (high latitudes), rays are more oblique and spread over a larger area, resulting in lower temperatures. This creates distinct latitudinal temperature zones (tropical, temperate, polar).
Example: Equatorial regions like the Amazon Basin are consistently hot, while polar regions like Antarctica are perpetually cold.
Altitude (Elevation): Temperature generally decreases with increasing altitude in the troposphere at a rate called the Normal Lapse Rate (approx. 6.5°C per 1000m). This is because the atmosphere at higher altitudes is less dense and contains fewer greenhouse gases to absorb and retain heat.
Example: Even in tropical regions, mountains like the Himalayas or Andes have snow-capped peaks and colder climates than the plains below. Shimla is cooler than Chandigarh despite being at a similar latitude.
Distance from the Sea (Continentality): Land heats up and cools down much faster than water due to its lower specific heat capacity and lack of mixing.
Coastal Areas: Experience a maritime or equable climate with a smaller annual range of temperature, as the moderating influence of the ocean keeps summers cooler and winters milder.
Continental Interiors: Experience an extreme or continental climate with a large annual range of temperature, as they are far from the moderating influence of the sea, leading to hot summers and cold winters.
Example: Mumbai (coastal) has a much smaller annual temperature range than Delhi (continental) at a similar latitude.
Ocean Currents: Large masses of ocean water, either warm or cold, flow along coastlines and significantly influence the climate of adjacent landmasses. Warm currents bring warmth and moisture, while cold currents bring cooling and often lead to aridity.
Example: The warm North Atlantic Drift keeps the coasts of Western Europe milder in winter than expected for their latitude. The cold Peru Current contributes to the aridity of the Atacama Desert in South America.
Wind Systems (Prevailing Winds): Winds carry the characteristics (temperature, moisture) of the regions from which they originate.
Example: Winds blowing from warm oceans onto land bring moisture and rain (e.g., summer monsoons in India). Winds blowing from cold continental interiors bring dry, cold conditions (e.g., winter winds in North America).
Relief (Topography): Mountains act as significant barriers to air masses and wind systems.
Windward Side: The side facing the wind receives heavy orographic rainfall as moist air is forced to rise, cool, and condense.
Leeward Side (Rain Shadow): The side away from the wind is dry because the air descends, warms, and dries out, creating arid or semi-arid conditions.
Example: The Western Ghats in India receive heavy rainfall on their western slopes (windward side), while the Deccan Plateau to their east lies in a rain shadow.
Explain the formation, characteristics, and impacts of Tropical Cyclones.
Answer:
Tropical Cyclones (also known as hurricanes in the Atlantic, typhoons in the Pacific, or simply cyclones in the Indian Ocean) are intense low-pressure systems that develop over warm tropical oceans. They are characterized by a violently rotating mass of air, torrential rainfall, and destructive winds.
Formation of Tropical Cyclones:
Tropical cyclones require a specific set of conditions to form:
Warm Ocean Waters: Sea surface temperatures must be at least 27°C (80°F) down to a depth of about 50 meters, providing sufficient moisture and latent heat.
Low Coriolis Force: They typically form between 5° and 30° latitude in both hemispheres. The Coriolis force, which is absent at the equator, is necessary to initiate and sustain the rotational motion.
Pre-existing Low-Pressure Area/Disturbance: A weak low-pressure system or a pre-existing atmospheric disturbance (like an easterly wave) acts as a trigger.
High Humidity: Sufficient moisture content in the lower to mid-troposphere is essential for cloud formation and the release of latent heat.
Low Vertical Wind Shear: Minimal change in wind speed or direction with height (wind shear) is required. High shear can tear the developing storm apart.
The process begins when warm, moist air above the ocean surface rises. As it rises, it cools, and water vapor condenses, releasing a massive amount of latent heat. This heat warms the surrounding air, making it more buoyant and causing it to rise further, intensifying the low-pressure system at the surface. Air from surrounding areas rushes in towards the low-pressure center, gets warmed and humidified, and then rises, creating a continuous feedback loop. The Coriolis force deflects the incoming air, causing it to spiral inwards and upwards, leading to the characteristic cyclonic rotation (counter-clockwise in the Northern Hemisphere, clockwise in the Southern Hemisphere). The central area, called the Eye, remains calm and clear due to sinking air.
Characteristics of Tropical Cyclones:
Compact Size: Relatively smaller in diameter (100-2000 km) compared to temperate cyclones.
Intense Low Pressure: Extremely low pressure at the center (the eye), leading to steep pressure gradients and very strong winds.
Eye and Eyewall: A calm, clear eye (typically 10-50 km in diameter) at the center, surrounded by the eyewall, a dense wall of towering cumulonimbus clouds where the strongest winds and heaviest rainfall occur.
Spiral Bands: Beyond the eyewall, rainbands spiral outwards, containing thunderstorms and occasional tornadoes.
High Wind Speeds: Winds can exceed 200 km/h, causing immense destruction.
Heavy Precipitation: Torrential rainfall, often leading to widespread flooding.
Warm Core: They have a warm core due to the release of latent heat.
No Fronts: Unlike temperate cyclones, they do not have distinct warm or cold fronts.
Impacts of Tropical Cyclones:
Tropical cyclones cause widespread devastation in coastal and nearby inland areas:
Storm Surge: This is often the most dangerous impact. A massive rise in sea level caused by the cyclone's strong winds pushing water towards the coast and the low atmospheric pressure. It can inundate vast low-lying coastal areas, causing immense loss of life and property.
High Winds: Destructive winds can demolish buildings, uproot trees, damage infrastructure (power lines, communication towers), and turn loose objects into dangerous projectiles.
Torrential Rainfall and Flooding: Extremely heavy rainfall leads to widespread flash floods, riverine floods, and landslides, disrupting transportation, damaging crops, and contaminating water supplies.
Coastal Erosion: Powerful waves and storm surges cause significant erosion of beaches, dunes, and coastal structures.
Loss of Life and Property: The combined effects of wind, water, and surge result in significant fatalities, injuries, displacement of populations, and massive economic losses from damage to homes, businesses, and agriculture.
Long-term Environmental and Economic Disruption: Impacts can disrupt ecosystems, salinize agricultural lands, and cripple local economies for years.
