Atmosphere and weathering (content) Flashcards
Diurnal energy budgets, The global energy budget, Weather processes and phenomena, The human impact
Define “climate”
long term average conditions in the atmosphere (temperature, humidity, precipitation)
What determines the Earth’s energy budget?
The inputs, throughputs and outputs of heat energy in the atmosphere together determine Earth’s energy budget. It’s the energy budget that governs Earth’s temperature and therefore drives our weather & climate.
What is convection?
Convection is a heat transfer process involving the movement of fluids, whether liquids or gases.
When a fluid is heated, particles become more energetic, expand, and become less dense, creating an ascent.
Colder and denser particles then fill the vacant space, creating a continuous flow.
What is insolation?
During the day, the sun makes energy in the form of shortwave solar radiation.
This solar radiation is either reflected or absorbed.
what affects the amount of insolation an area receives?
The angle of incidence of the suns rays
which is in turn affected by:
Latitude
Time of day
Season
Cloud cover
What is Albedo, and how does it affect levels of insolation?
the ratio of reflected to incoming solar radiation, measured as a percentage.
It is expressed from 0, the lowest to 1, the highest
It can also be expressed as a percentage.
What is specific heat capacity?
The rate of solar absorption different surfaces have.
e.g the oceans have really high specific heat capacities, as they take ages to warm up.
What is surface absorption?
Once the sun’s rays hit a surface, what energy is not reflected is absorbed by that surface and heats up.
What dictates the amount of HEAT that is absorbed through surface absorption?
Heat has the potential to be conducted downwards from Earth’s surface into the soil/rock and stored.
How much this happens is controlled by the nature of the material and its Thermal conductivity
Rock is a poor thermal conductor, what will this mean for surfaces covered in rock?
Water is a great thermal conductor, what will this mean for surfaces covered in ocean? Also, why is water such a good conductor?
Rock will rapidly heat up in the day/summer, and release all their heat at night/winter, not storing any.
Water will take a long time to heat up during the day/summer, and stores more heat in the winter/night.
Water is a good conductor because it is subject to convection and is a fluid.
What is outgoing radiation/long wave radiation?
As the ground warms, due to insolation, heat is re-radiated as relatively weak, long wave ‘thermal’ radiation back into the atmosphere.
This is caught by gases, particularly greenhouse gases like carbon dioxide, water vapour and methane
As a result, much of the heat energy in the lower atmosphere is the result of LW terrestrial radiation, rather than direct heating from the sun.
This goes some way to explaining why temperatures drop with altitude.
some long wave radiation does escape into space.
What is sensible heat transfer?
The transfer of warmer and cooler parcels of air through convection and winds.
What is sensible heat?
sensible heat is heat given off or absorbed by a surface.
it is predominately given off from the surface and pulled up into the air through convection, producing thermals.
What are thermals
thermals are parcels of warm, rising air.
Thermals move heat up vertically, but wind can move the thermals horizontally, influencing the local energy budget.
What is Latent heat?
As water evaporates through insolation, it takes up energy from its surroundings to change state. This creates “latent heat”
This heat is released from the water when it condenses into a cloud.
absorption of energy during evaporation causes a drop in temperature in its surroundings.
The opposite occurs when condensation occurs, increasing the temperature of the surrounding atmosphere.
This therefore affects the amount of energy available to raise local energy levels and temperatures.
What components are there of the 4 factor night model?
- Long wave radiation
- subsurface supply
- sensible heat transfer
- latent heat (condensation)
How does long wave radiation change in the night model?
The ground reradiates heat back into the atmosphere (LW radiation) and if there is cloudless sky then the majority of this heat is lost into space and cools.
If clouds are present then much of the LW radiation is reradiated downwards and temperatures do not change significantly.
How does sub surface supply work in the 4 factor night model?
The heat stored in the soil and subsoil during the day can be transferred to the cooled surface during the night.
This energy supply can offset overnight cooling, and reduce the size of the night-time temperature drop on the surface.
How does sensible heat transfer change at night?
Warm air moving to a given point (wind + convection) will contribute energy and keep temperatures up.
By contrast, if cold air moves in, energy levels will fall, with a possible reduction in temperature.
How does latent heat (condensation) change at night?
The radiation of heat from the Earth’s surface at night causes it to cool down at night.
Water vapour in the air close to the ground is cooled as a result, and it can condense to form dew.
The condensation process liberates latent heat, and supplies energy to the surface, resulting in a net gain of energy.
However, it is possible for evaporation to occur at night. If this happens on a significant scale a net loss of energy might result.
Overall summary of nighttime energy budget
There is long wave radiation loss at night (terrestrial radiation)
However on cloudy nights energy loss is reduced
Heat transferred by the sun to the surface during the day, may be released back to the surface at night, increasing temperatures.
Sensible heat transfer still occurs and cold air moving into an area may reduce temperatures whereas warm air moving in will raise temperatures
At night, water vapour in the air close to the ground can condense to form dew because the air is cooled by the cold surface. Heat is released during this process
How does latitude affect insolation?
1) Due to the earth’s curvature, insolation is more concentrated at lower latitudes.
2) Due to the earth’s curvature, insolation has to go through more atmosphere in the polar regions, leading to significant energy being lost there to reflection.
Thus an energy and temperature imbalance is created as the equator holds significantly more radiation than the polar regions.
If the poles are in deficit and the equator is in surplus, why are both locations not exponentially hot/cold?
Winds and ocean currents carry heat from the equator, to the poles
Firth:
A balance is achieved by the horizontal transfer of energy from the equator to the poles by winds and ocean currents to compensate for differences in global insolation
Where is the Thermal Equator?
The Thermal Equator is the hottest region of the planet.
It moves depending on the time of year.
In December/ January it is over the Tropic of Capricorn (23.5 south)
In June/ July it is over the Tropic of Cancer (23.5 north)
