Daytime + Night-time Energy Budgets

Question 1

What are the factors affecting diurnal energy budgets?

Answer 1

• incoming (shortwave) solar radiation
• reflected solar radiation
• surface/subsurface absorption
• albedo
• sensible heat transfer
• longwave radiation
• latent heat transfer: evaporation, dew + absorbed energy returned to Earth

Question 2

What are the components of a day time energy budget?

Answer 2

• incoming (shortwave) solar radiation
• reflected solar radiation
• surface/subsurface absorption
• sensible heat transfer
• longwave radiation
• latent heat (evaporation + condensation)

Question 3

What are the components of a night-time energy budget?

Answer 3

• longwave Earth radiation
• latent heat transfer
• absorbed energy returned to Earth
• sensible heat transfer

Question 4

Incoming (shortwave) solar radiation

Answer 4

• radiation from sun that doesn’t all reach Earth’s surface due to some being scattered, reflected or absorbed
• affected by amount + type of cloud + sun’s angle
• 5% scattered by atmo.
• 24% reflected into space by atmo. (albedo)
• 23% absorbed by atmospheric gases
• 48% absorbed by Earth’s surface

Question 5

Reflected solar radiation (albedo)

Answer 5

• proportion of energy reflected back to atmo.
• light materials have higher albedo so reflect more radiation energy

Question 6

Surface/subsurface absorption

Answer 6

• darker surfaces absorb more radiation so energy has potential to transfer to lower layers via conduction
  
  • so surface remains cool
  • heat released back to surface at night
• if energy concentrated at surface, it warms up

Question 7

Longwave radiation

Answer 7

• radiation of energy from Earth into atmo. + space
• easily absorbed by greenhouse gases + clouds: returns some heat to surface
• during day = net loss of energy
• cloudy nights = energy loss dec.
• cloudless nights = largest energy lost

Question 8

Sensible heat transfer

Answer 8

• heat transferred from ground to air by:
  
  • convection: air warmed by surface, begins to rise + is replaced by cooler air
  • conduction: causes heat transfer between ground + air

Question 9

Latent heat transfer

Answer 9

• when water evaporates into vapour, heat energy is absorbed: leaves less energy to heat surface
• evaporation: water absorbs energy, turns to gas + leaves surface: so surface + air cools
• dew: water vapour near surface condenses, releasing latent heat: adds heat to ground
• absorbed energy returned to Earth: greenhouse gases absorb reradiated longwave radiation, warming atmo.