Solar Radiation, Heat Balance, and Temperature 

Current Context

• Global warming due to increased greenhouse gas (GHG) emissions affecting Earth’s heat balance.
• Extreme temperature variations worldwide due to climate change and urban heat islands.
• Changes in solar activity and sunspot cycles affecting Earth’s climate patterns.

Solar Radiation

• Definition: Energy emitted by the Sun in the form of electromagnetic waves (UV, visible, and infrared).
• Solar Constant: The amount of solar radiation received at the top of the atmosphere (1.366 kW/m² or ~2 cal/cm²/min).
• Insolation:
  • The incoming solar radiation received on Earth’s surface.
  • Factors affecting insolation:
    • Latitude (higher latitudes receive less insolation).
    • Time of the year (seasonal variations due to Earth’s tilt).
    • Cloud cover (reduces solar radiation reaching the surface).
    • Altitude (higher latitudes receive more insolation due to thinner atmosphere).

Heat Budget (Earth’s Heat Balance)

• The balance between incoming solar radiation and outgoing terrestrial radiation.
• Components of Heat Budget:
  • Incoming Solar Radiation (100%)
    • Absorbed by atmosphere (14%)
    • Absorbed by Earth’s surface (51%)
    • Reflected by atmosphere and clouds (20%)
    • Reflected by Earth’s surface (6%)
  • Outgoing Terrestrial Radiation
    • Radiated back by Earth’s surface (17%)
    • Transferred via convection and conduction (23%)
    • Radiated back by clouds and atmosphere (60%)
• Albedo Effect: The percentage of solar radiation reflected back by a surface.
  • Earth’s average albedo: ~30%
  • Snow-covered regions have higher albedo (~80-90%).
  • Oceans and forests have lower albedo (~10-20%).

Temperature Distribution on Earth

• Factors affecting temperature distribution:
  • Latitude: Higher latitudes receive less insolation due to the curvature of Earth.
  • Altitude: Temperature decreases with height due to decreasing atmospheric pressure.
  • Continentality (Land-Water Contrast): Water bodies moderate temperature; interiors of continents have extreme temperatures.
  • Ocean Currents: Warm currents increase temperatures (e.g., Gulf Stream), cold currents lower temperatures (e.g., Labrador Current).
  • Wind and Air Masses: Influence regional temperature variations.
  • Cloud Cover: Reduces diurnal temperature variation by blocking solar radiation.

Inversion of Temperature

• Definition: A phenomenon where temperature increases with altitude instead of decreasing.
• Causes:
  • Radiation Cooling: Occurs on cold nights with clear skies.
  • Subsidence (Sinking Air): High-pressure systems lead to stable atmospheric layers.
  • Valley Inversions: Cold air gets trapped in valleys.
• Effects:
  • Traps pollutants and causes smog formation (e.g., Delhi, Beijing).
  • Affects agriculture by increasing the risk of frost damage.

Conclusion

1.Solar radiation and heat balance regulate Earth’s climate and weather patterns.

2.Human activities, such as greenhouse gas emissions, are altering this balance, leading to climate change.

3.Understanding temperature distribution and inversions is crucial for studying global warming and urban climate effects.

MCQ PRACTICE
1. Consider the following statements regarding Solar Radiation:

1. Solar radiation consists of ultraviolet (UV), visible, and infrared waves.
2. The Solar Constant is the total amount of solar radiation received at the Earth’s surface.
3. Higher altitudes receive less insolation due to a thicker atmosphere.

Which of the statements given above is/are correct?
(a) 1 only
(b) 1 and 3 only
(c) 2 and 3 only
(d) 1, 2, and 3

Answer: (a) 1 only

2. Regarding Earth’s Heat Budget, consider the following statements:

1. The majority of incoming solar radiation is absorbed by Earth’s surface.
2. A significant portion of outgoing terrestrial radiation is radiated back by clouds and the atmosphere.
3. The amount of solar radiation reflected by the Earth’s surface is greater than that reflected by clouds and the atmosphere.

Which of the statements given above is/are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2, and 3

Answer: (a) 1 and 2 only

3. Consider the following statements regarding the Albedo Effect:

1. The Earth’s average albedo is approximately 30%.
2. Snow-covered regions have lower albedo than oceans.
3. Surfaces with higher albedo reflect more solar radiation.

Which of the statements given above is/are correct?
(a) 1 and 3 only
(b) 2 and 3 only
(c) 1 only
(d) 1, 2, and 3

Answer: (a) 1 and 3 only

4. Which of the following factors affect the temperature distribution on Earth?

1. Latitude and altitude
2. Ocean currents and wind patterns
3. Cloud cover and land-water contrast

Select the correct answer using the code given below:
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1, 2, and 3
(d) 1 only

Answer: (c) 1, 2, and 3

5. Regarding Temperature Inversion, consider the following statements:

1. It occurs when temperature increases with altitude instead of decreasing.
2. It is commonly observed in valleys and high-pressure regions.
3. It reduces the formation of smog and helps in pollution dispersion.

Which of the statements given above is/are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2, and 3

Answer: (a) 1 and 2 only

6. Consider the following statements regarding Insolation:

1. Insolation is the total amount of solar radiation received at the top of the atmosphere.
2. Cloud cover reduces the amount of insolation reaching the Earth’s surface.
3. Insolation varies with latitude, season, and altitude.

Which of the statements given above is/are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1, 2, and 3
(d) 1 and 3 only

Answer: (b) 2 and 3 only

7. Consider the following pairs of ocean currents and their effect on temperature:

Which of the pairs given above are correctly matched?
(a) 1 and 4 only
(b) 1, 2, and 3 only
(c) 1 and 3 only
(d) 1 and 2 only

Answer: (a) 1 and 4 only