Key Stuff Flashcards
Energy Budgets
models that help to analyse heating + cooling of the atmosphere
shortwave radiation
- incoming solar radiation (insolation)
- gets emitted from hot body e.g. sun
Longwave Radiation
- the radiation released from earth (1) usually during night time (1)
- LW radiation easily absorbed by GHG on way out, = greenhouse effect (trapped heat warms air)
radiation cooling
- when the ground cools as a result of outgoing longwave radiation (1)
- mostly @ night (1)
- calm conditions + clead skies (1)
how much of incoming SW is reflected
- 29%
- earth surface (6%)
- clouds (18%)
- scattered by atmospheric particles (5%)
how much of incoming SW is absorbed
- 23%
- scattered to atmosphere 5%
- absorbed by atmosphere 14%
- absorbed by clouds 4%
absorbed by surface
48%
what happens to absorbed 48%
- 12% re radiated to space directly through Space Window
- 5% conduction+convection -> sensible heat transfer
- 25% evap -> latent heat transfer
- 6% LW radiation from surface
albedo values
- cumulonimbus cloud
- fresh snow
- concrete
- grass
- asphalt
- tarmac
- 92
- 80
- 22
- 25
- 10
- 5-10
sensible heat transfer
- caused by the movement of parcels of air (1) into and out of an area usually by convection/conduction taking its heat with it (1)
- i.e. change of temp, but no change of state
latent heat transfer
- the heat transferred without a change of temperature (1) following a change of state (1), e.g. gas -> liquid, liquid -> gas
albedo
the % of incoming SW radiation (1) that is reflected back into space from a surface (1)
conduction
transfer of heat as a result of CONTACT
- from solid surface to atmosphere
convection
upward movement of air (1) caused as a result of surface heating (1) resulting in less dense air (1)
evap
change in state from liquid to gas (1) as a result of heating (1)
condensation
formation fo water droplets (gas to liquid) (1) as a result of a drop in temp to the dew point (1)
diurnal budget
24 hour period, encompassing day and night time energy budgets
day time energy budget
6 factor model
- incoming SW solar radiation
- reflected SW solar radiation
- absorbed solar radiation
- re-radiated LW radiation
- sensible heat transfers
- latent heat transfers
evaluating incoming Sw radiation (day)
- input will vary spatially + temporally
- depending on latitude + seasonality due to tilt of earth
evaluating reflected SW radiation (day)
depends on albedo, as amount reflected then changes amount absorbed etc, can change whole budget
evaluating surface absorption (day)
- nature of surface
–dark granite has low albedo + good conductor so easy absorbs radiation, stores deep under surface to re radiate later
– light limestone has high albedo + bad conductor so doesn’t absorb well, heat in surface layers - moisture helps conductivity
- Urban areas have higher SA than rural, so more absorption
evaluating latent heat transfer (day)
- more water will mean more LHT occurs, e.g. at lakes, rivers, vegetation etc. means that in these rural areas there will be more temp lost than in urban areas
evaluating sensible heat transfers (day)
- conduction doesnt tranfer as much heat as convection
evaluating LW radiation (day)
- GHG in atmosphere better at absorbing LW, so warms atmosphere.
- clouds also good at absorbing LW, trap it in atmosphere
- creates greenhouse effect
night time energy budget (4 factor model)
- heat absorbed into surface + given out by conduction
- LW radiation (output)
- sensible heat transfers
- latent heat transfers
evaluating heat absorbed into surface + given out by conduction (night)
- heat absorbed in day can be re-radiated at night, can offset radiation cooling
- material w high thermal capacity (brick, concrete, stone) can absorb + store lots of heat during day, release slowly @ night as LW
evaluating latent heat transfers (night)
- radiation cooling @ surface means cold surfaces cool air above them, to dew point temp.
- any water vapour will condense
- condensation releases latent heat, providing energy to atmosphere, meaning net gain of energy
evaluating sensible heat transfers (night)
- with no insolation, less sensible heat losses at night.
- HOWEVER, at tropics sensible heat transfers may still occur without solar radiation
- w/ no SW, convection less important.
evaluating LW radiation (night)
- if cloudless, LW will escape easily
- if cloudy, clouds will absorb and re-radiate to surface, trapping it in lower atmosphere, so less energy loss, less radiation cooling
why is there a surplus of radiation energy in some parts of the world and a deficit in the others?
- angle of overhead sun - tilt and curvature of earth
- sun always overhead the equator, high intensity @eq.
- @poles, insolation v. dispersed, less intense. travels through more atmosphere on way to poles bcz angle - tilt of earth + seasonality
- higher latitudes, insolation amount received by earth surface varies seasonally + decreases overall
- @poles, less direct sun, less/no insolation for many months - albedo
- poles, snow, high reflectivity (75-95%), so incoming SW reflected, therefore temp low
- dark oceans, forests, urban absorb much more
cells
hadley (@equator) -> ferrel (middle) -> polar (near poles)
