2.1 Local energy budgets Flashcards Preview

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Flashcards in 2.1 Local energy budgets Deck (21)
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1
Q

Define energy budget

A

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

2
Q

What are the 6 components of the daytime energy budget?

A
  • Incoming solar radiation (insolation)
  • Reflected solar radiation (albedo)
  • Surface absorption
  • Sensible heat transfer
  • Long wave radiation
  • Latent heat (evaporation)
3
Q

Define daytime energy budget

A

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

4
Q

Define insolation and its role in the daytime energy budget

A
  • 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
5
Q

Define albedo and its role in the daytime energy budget

A
  • 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
6
Q

Define surface absorption and its role in the daytime budget

A
  • 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)
7
Q

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

A
  • 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
8
Q

Define long wave radiation and its role in the daytime budget

A
  • 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
9
Q

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

A

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

10
Q

Longwave radiation’s role in the night time energy budget

A
  • 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
11
Q

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

A

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

12
Q

Sensible heat transfer’s role in the nightime energy budget

A

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

13
Q

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

A

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

14
Q

What are mist and fog?

A
  • 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
15
Q

Differences between mist and fog?

A
  • Mist occurs when the visibility is between 1000m-5000m
  • Fog occurs where visbibility is below 1000m => fog is thicker than mist
16
Q

Conditions for fog and mist to occur

A
  • 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
17
Q

Advection fog

A

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)

18
Q

Radiation fog

A

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

19
Q

What is dew and how does it occur?

A
  • 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
20
Q

Define temperature inversions

A
  • 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
21
Q

Why does temperature inversion happen?

A
  • 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