FYUG Even Semester Exam, 2025 PHYSICS (Course No.: PHYIDC-151) Understanding the Climate

(a) What is percentage of oxygen in the atmosphere?
Oxygen accounts for approximately 21% of the Earth's atmosphere by volume.

(b) What is the lowest layer of Earth's atmosphere?
The Troposphere is the lowest layer, extending from the Earth's surface to about 8-15 km high.

(c) How does temperature vary with height in the troposphere?
In the troposphere, temperature decreases as the height increases.

(d) The atmospheric pressure increases with height. (True/False)
False. Atmospheric pressure decreases with height.

(e) What is the function of mesosphere layer?
The mesosphere protects Earth by burning up most meteors and asteroids before they can reach the surface.

Explain greenhouse effect in brief.

The greenhouse effect is a natural process where certain gases in the atmosphere trap heat from the sun, preventing it from escaping back into space, thereby keeping the planet warm enough to support life.

Describe the composition and vertical structure of the atmosphere. Explain the role of gases in heating and the heat budget.

1. Composition: The atmosphere is primarily composed of Nitrogen (78%), Oxygen (21%), and trace gases like Argon (0.93%) and Carbon Dioxide (0.04%).
2. Vertical Structure:

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• Troposphere: Weather occurs here; temperature drops with height[span_8](end_span).
• Stratosphere: Contains the ozone layer; temperature rises with height.
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• Mesosphere: Meteors burn here; coldest layer[span_11](end_span).
• Thermosphere: Absorbs high-energy X-rays; temperature increases significantly.
• Exosphere: The outermost layer merging with space.

3. Earth's Heat Budget: It is the balance between incoming solar radiation (shortwave) and outgoing terrestrial radiation (longwave). This balance ensures a stable global temperature.

(a) Is cloud seeding artificial?
Yes, cloud seeding is an artificial weather modification technique.

(b) What is the size of aerosol?
Aerosols typically range in size from 0.001 micrometers to 100 micrometers.

(c) What is trade wind?
Trade winds are permanent eastward-to-westward winds that flow in the Earth's equatorial region.

(d) Define humidity.
Humidity is the measure of the amount of water vapor present in the air.

Describe meteorological observation methods and the process of cloud formation.

1. Observation Methods:

• Surface Weather Stations: Measure temperature, pressure, and wind at ground level.
• Upper Air Observation: Uses weather balloons (radiosondes) to gather data from higher altitudes.
• Satellite Observation: Provides global images and data on cloud cover and atmospheric movement.

2. Cloud Formation: Occurs when water vapor cools and condenses around microscopic particles called aerosols (condensation nuclei). As these droplets grow and combine, clouds are formed, eventually leading to precipitation.

(a) What is trace gas?
Trace gases are gases that make up less than 1% of the Earth's atmosphere (e.g., CO2, Methane).

(b) Name the natural cause of climate change.
Natural causes include volcanic eruptions, solar variations, and orbital changes.

(c) Define global warming.
Global warming is the long-term increase in Earth's average surface temperature due to human activities.

(d) Is El Niño causing heatwaves?
Yes, El Niño can lead to significant shifts in global weather patterns, often increasing the frequency of heatwaves.

Describe the greenhouse effect and its role in global warming. How do gases impact weather patterns?

The greenhouse effect occurs when greenhouse gases (GHGs) like CO2 and Methane absorb infrared radiation. Increasing concentrations of these gases enhance this effect, leading to global warming.

Impact on Weather Patterns:

• Hurricanes: Warmer ocean temperatures provide more energy, making hurricanes more intense.
• Heatwaves: Rising global temperatures make extreme heat events more frequent and severe.

(a) Define fossil fuel.
Fossil fuels are natural fuels (like coal or gas) formed from the remains of living organisms.

(b) What is the effect of melting of glaciers?
Glacier melting leads to sea level rise and loss of freshwater habitats.

(c) What is carbon footprint?
The total amount of greenhouse gases produced by our actions, expressed as carbon dioxide equivalent.

(d) Why is industrialization a major cause of climate change?
Because it involves large-scale burning of fossil fuels and deforestation, releasing massive amounts of CO2.

Describe major manifestations of global warming and the effect of urban heat islands.

1. Global Warming Manifestations:

• Sea Level Rise: Caused by thermal expansion of water and melting ice sheets.
• Glacier Melting: Rapid reduction of polar ice and mountain glaciers.
• Monsoon Variation: Changes in the timing and intensity of seasonal rains.

2. Urban Heat Islands (UHI): Urban areas become significantly warmer than surrounding rural areas due to human activity, concrete surfaces, and lack of vegetation, which alters local micro-climates.

Explain Adaptation vs Mitigation, Geo-engineering, and Panchamrit.

1. Adaptation vs Mitigation:

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• Mitigation: Actions to reduce or prevent the emission of greenhouse gases (e.g., using solar energy)[span_39](end_span).
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• Adaptation: Adjusting to current or expected climate change effects (e.g., building sea walls)[span_41](end_span).

2. Geo-engineering: Large-scale technological interventions to manipulate the environment and offset global warming (e.g., solar radiation management).
3. Panchamrit: India's five-point climate action plan presented at COP26, focusing on non-fossil energy capacity, renewable energy targets, and achieving net-zero by 2070.