2.1 Local Energy Budgets

• Layers of the Atmosphere

  troposphere, stratosphere, mesosphere, thermosphere

  
• troposphere layer characteristics

  decrease of temperature with height

  increase in winds with height

  fall in pressure with height

  unstable layer due to presence of cloud, pollution and water vapour and dust

  contains earths weather
• stratosphere layer characterisitics

  Ozone is concentrated, which absorbs UV radiation from the sun.
• Mesosphere layer characterisitics

  Rapid fall in temperature with height, caused by a lack of water vapour, cloud and dust.

  low temp and high wind
• Thermosphere layer characterisitics

  outer layer of the atmostphere

  rapid increase in temp over 1000
• Energy budget


  the amount of energy entering, leaving and transferring within the system
• how does the earth redistribute energy around

  the earth uses pressure belts, winds and ocean currents.
• percentage of insolation that reaches the earths surface

  47%
• daytime energy budget (six processes)

  Insolation

  reflected solar radiation

  surface absorption

  latent heat

  sensible heat transfer

  long wave radiation

  
• daytime insolation


  main energy input influenced strongly y cloud cover and latitude. Rays more concentrated at equator than at poles
• daytime reflected solar radiation

  snow and ice have highest albedos reflecting 95 % of sunlight

  Ocean surfaces absorb the most sunlight
• daytime surface absorption

  energy arriving at the surface has the potential to heat it.

  different surfaces have different heat capacitys
• daytime latent heat

  transformation of liquid into vapor consumes a considerable amount of energy.

  water that is present at the surface a proportion of the incoming solar radiation will be used to evaporate it.
• daytime sensible heat transfer


  refers to the movement of parcels of air into and out from the area being studied.
• daytime long wave radiation


  emitted by the surface and into space

  since the outgoing steam is greater than the incoming one, there is a net loss of energy from the surface
• 4 components of night time energy budgets

  long wave radiation

  latent heat (condensation)

  sensible heat transfer

  subsurface supply
• night time longwave radiation


  cloudless nights means large amount of long radiation lost and very little return of radiation from the atmosphere.

  loss is reduced during cloudy nights
• Latent heat (condensation)


  at night water vapor in the air close to the ground can condense and form dew as the air is cooled y the cold surface. This releases stored energy, resulting in a net gain of energy.
• Subsurface supply


  heat transferred by the sun to the surface during the day, may be released back to the surface at night which can off set the night time cooling at the surface
• sensible heat transfer

  still occurs and cold air moving into an area may reduce temperature whereas warm air moving in will raise temperatures.
• absolute humidity


  referes to the amount of water in the atmostphere
• relative humidity


  refers to the water vapour present expressed as a percentage of the max amount air at that temp can hold
• dew point


  the temperature at which condensation occurs, allowing the formation of dew, mist or fog.
• fog formation

  form at ground level because, air can only hold a certain amount of moisture. (cold holds less than hot) once maximum amount of moisture is reached, air is saturated and the water vapor in the air turns to liquids (dew point).
• for clouds of fog/mist to occur one of 2 things must happen?

  1 Air must have been cooled close to the ground

  2 more water vapour must have been added to the atmosphere close to the ground

  - can occur over warm, wet surfaces like a lake.
• advection fog


  a fog formed when warm, moist air is blown over a cool surface
• radiation fog

  condensation of water vapor that results from the cooling of air that is in contact with the ground
• temperature inversion

  atmospheric condition in which warm air traps cooler air near the earth's surface

  
• case study svalbard norway

  - during summer the net short wave radiation is the dominant energy source

  sensible heat transfers and surface absorption in the ground lead to a cooling of the surface

  - 15 percent on net radiation is used up by seasonal thawing

  - net long wave radiation is the dominant energy loss channel for the surface

  -when the ground is covered by snow, latent heat fluxes through sublimation of snow are recorded but are insignificant for the average surface energy budget