2.1 Local Energy Budgets

Question 1

Energy Budget

Answer 1

The amount of energy entering a system, the amount leaving the system, and the transfer of energy within the system. They are considered at a global scale (macro-scale) and at a local scale (micro-scale)

Question 2

6 components of the daytime energy budget

Answer 2

1) Incoming solar radiation (insolation)
2) Reflected solar radiation (albedo) + Scattering
3) Surface Absorption
4) Latent Heat Transfer (evaporation)
5) Sensible Heat Transfer
6) Long-wave Radiation

Question 3

Insolation

Answer 3

The amount of incoming solar radiation that reaches the Earth’s surface. It is the main energy input and is affected by latitude, season and cloud cover. The less cloud cover there is and/or higher the cloud, the more radiation reaches the Earth’s surface.

Question 4

Albedo

Answer 4

The percentage of energy that is reflected back to the atmosphere. This varies with colour - light materials are more reflective than dark materials.

Question 5

Surface Absorption

Answer 5

• About 40% of the solar radiation that hits the atmosphere is absorbed
• 1/2 of solar radiation that arrives on Earth is scattered light
• absorption of radiation involves the conversion of solar radiation (light energy) into heat energy (long wave radiation). This causes the Earth’s surface to heat up.
• absorption is uneven

Question 6

Albedo of Grass

Answer 6

Grass has an average albedo of 20-30%, meaning that it reflects back about 20-30% of the radiation it receives

Question 7

Sensible Heat Transfer (day-time)

Answer 7

• “sensible” - can be felt by senses.
• Heat energy moving from 1 substance to another, changes temperature rather than phase
• Heat energy is transferred vertically into the atmosphere by convection - unequal heating of atmosphere
• Heat energy transferred to the air from ground by conduction. Heat energy passes through the molecules of the solid ground, transferred to the air above

Question 8

Long-Wave radiation (day-time)

Answer 8

• most of the energy absorbed by the Earth’s surface is re-radiated back into the atmosphere as long wave radiation
• As the Earth has a much lower temperature than the sun, the radiation it emits is weaker and has longer wavelengths than insolation

Question 9

Latent Heat Transfer (evaporation)

Answer 9

Occurs when heat energy is used to turn liquid water into water vapour. In contrast, when water vapour becomes a liquid, heat is released. Thus, when water is present at a surface, a proportion of the energy available will be used to evaporate it, and less energy will be available to raise local energy levels and temperature

Question 10

4 components of the night-time energy budget

Answer 10

1) Long wave Radiation
2) Latent Heat Transfer (condensation)
3) Sub-surface Supply
4) Sensible Heat Transfer

Question 11

Long Wave Radiation (night-time)

Answer 11

During a cloudless night, there is a large loss of long-wave radiation from the Earth. On a cloudy night, in contrast, the clouds return some long-wave radiation to the surface, hence the overall loss of energy is reduced

Question 12

Latent Heat Transfer (condensation) (night-time)

Answer 12

This Is released when water condenses. During the night, water vapour in the air close to the surface can condense to form water, since the air has been cooled by the cold surface.

Question 13

Sub-Surface Supply

Answer 13

Refers to the heat transferred to the soil and bedrock during the day, which is released back to the surface at night. This can partly offset the night-time cooling at the surface.

Question 14

Sensible Heat Transfer (night-time)

Answer 14

Refers to air movement. Cold air moving into an area may reduce temperatures whereas warm air may supply energy and raise temperatures.

Question 15

Albedo of Water (Sun’s angle over 40 degrees)

Answer 15

Albedo of 2-4%. It reflects back about 2-4% of the radiation it receives

Question 16

Albedo of Water (Sun’s angle less than 40 degrees)

Answer 16

Albedo of 6-80%. It reflects back about 6-80% of the radiation it receives

Question 17

Temperature Inversion

Answer 17

A relative increase in temperature with height in the lower part of the atmosphere. This happens when there are relatively calm (high pressure) conditions and little mechanical turbulence from the wind causing the air to mix.

Question 18

Reflected Solar Radiation

Answer 18

• 20% of the reflection occurs in clouds
• 4% of solar radiation is reflected from the Earth’s surface
• amount of reflection depends on surface

Question 19

Scattering

Answer 19

• occurs when solar radiation hits microscopic objects in the Earth’s atmosphere such as gas molecules, dust particles
• These spread the solar radiation in all directions
• However, more is dispersed in the forward direction