2.1 Local energy budgets

Question 1

Define energy budget

Answer 1

An energy budget refers to the amount of energy entering a system, the amount leaving the system and the transfer of energy within the system

Question 2

What are the 6 components of the daytime energy budget?

Answer 2

• Incoming solar radiation (insolation)
• Reflected solar radiation (albedo)
• Surface absorption
• Sensible heat transfer
• Long wave radiation
• Latent heat (evaporation)

Question 3

Define daytime energy budget

Answer 3

Assumes a horizontal surface with grass-covered soil. It is expressed by the formula: energy available at surface = incoming solar radiation - (6 components)

Question 4

Define insolation and its role in the daytime energy budget

Answer 4

• The amount of incoming heat energy from the Sun that reaches the Earth’s surface
• Main energy input and is affected by latitude, season and cloud cover

Question 5

Define albedo and its role in the daytime energy budget

Answer 5

• The proportion of energy that is reflected back to the atmosphere
• Varies with colour - light materials are more reflective than dark materials
• It is important because it reflects the incoming solar radiation, therefore, helps to keep the earth cooler and limits global warming => halt the rising of sea level whih can consequent as an increase in natural hazards

Question 6

Define surface absorption and its role in the daytime budget

Answer 6

• Refers to the energy that reaches the Earth’s surface and heat it due to conduction (energy being absorbed). From solar energy to heat energy
• Amount of energy absorbed depends on the material (rock is a poor conductor)

Question 7

Define sensible heat transfer and its role in the daytime energy budget

Answer 7

• Refers to the movement of parcels of air into and out of the area
• 3 types of heat transfer: radiation, convection and conduction
• Convection: the process by which heat is transferred by movement of a heated fluid (gas/liquid)
• Radiation: the transfer of heat by electromagnetic waves. This form of transfer do not need a medium for travel
• Conduction: the transfer of heat across 2 materials which have physical contact with each other
• During daytime, convection - warm air rises and is replaced by cold air

Question 8

Define long wave radiation and its role in the daytime budget

Answer 8

• Refers to the radiation of energy from Earth to atmosphere and some to the space
• 2 types: outgoing longwave radiation and incoming longwave radiation
• Difference between 2 flows is the net radiation balance
• During day: outgoing < incoming

Question 9

Define latent heat transfer (evaporation) and its role in the daytime energy budget

Answer 9

Energy is used to turn liquid water into water vapour - to evaporate water => less energy available to raise local energy levels and temperature (groud less hot). Involves a change in state

Question 10

Longwave radiation’s role in the night time energy budget

Answer 10

• There is long wave radiation loss as often nights are cloudless so there is nothing to return the long wave radiation back to the surface
• Outgoing > incoming => radiation loss

Question 11

Latent heat transfer (condensation)’s role in the nightime energy budget

Answer 11

Water vapour in the air close to ground can condense to form dew because the air is cooled by the cold surface. Involves a change in state

Question 12

Sensible heat transfer’s role in the nightime energy budget

Answer 12

Cold air moving into an area reduce temperature whereas warm air moving in will raise temperature

Question 13

Define sub-surface supply and its role in the nightime energy budget

Answer 13

Heat transferred to the soil and bedrock during the day and may be released back to the surface at night => offer night time cooling

Question 14

What are mist and fog?

Answer 14

• Cloud = collection of water droplets
• Are clouds that are formed at ground level because air can only hold a certain amount of moisture (colder air can hold less moisture than warmer air). Condensation can take place in 2 ways: air is cooled or more water is added to the atmosphere

Question 15

Differences between mist and fog?

Answer 15

• Mist occurs when the visibility is between 1000m-5000m
• Fog occurs where visbibility is below 1000m => fog is thicker than mist

Question 16

Conditions for fog and mist to occur

Answer 16

• Condensation nuclei: dust, salt
• Calm, high pressure conditions. If there is a low pressure system, winds will prevent fog from forming by mixing the air

Question 17

Advection fog

Answer 17

As warm, moist air passes over a cold surface it is chilled, and condensation takes place as the temperature of the air is reduced and therefore it reaches dew (saturation) point)

Question 18

Radiation fog

Answer 18

Occurs when the ground loses heat at night by long wave radiation and therefore the air above it is cooled causing condensation and fog.

Question 19

What is dew and how does it occur?

Answer 19

• Refers to condensation on a surface
• Air is saturated because temperature of surface has dropped enough to cause condensation
• Occasionally, condensation occurs because more moisture is introduced, for example, sea breeze while the temperature remains constant

Question 20

Define temperature inversions

Answer 20

• Means that there is an abnormal layer of warmer air above colder air in the troposphere
• Often happens at night in calm conditions, so it sometimes known as a nocturnal inversion

Question 21

Why does temperature inversion happen?

Answer 21

• During the day, the ground is heated by the sun’s short wave radiation. It then heats the air above it when it emits long wave radiation
• At night, both the ground surface and air lose heat energy they absorbed during the day. Ground loses heat energy faster because it is a better heat conductor
• By the end of the night, ground surface is cold => air directly above it will be cooled => air layer above will be warmer