Samenvatting
Natural processes samenvatting
Samenvatting van college aantekeningen aangevuld met stof uit het boek. Summary of college notes with supplemented with material from the book.
[Meer zien]Voorbeeld 4 van de 36 pagina's
Voorbeeld 4 van de 36 pagina's
In winkelwagengesponsord bericht van onze partner
Voorbeeld van de inhoud
Natural processes GEO1-2412Lecture 1 – Energy in the atmosphere
Surface > troposphere > stratosphere
Troposphere= decline in temperature with height (warm air rises and cools down). (humans)
Stratosphere= stable layer, hardly any mixing unlike troposphere. (contains ozon layer)
CO2 in the atmosphere:
It is not accumulating, because we would have suffocated. 20-30% taken up by vegetation and 25%
by the ocean. Long-term CO2 cycle includes chemical weathering.
Forms of energy: kinetic, potential, heat, chemical and radiation.
Intensity of radiation is related to the wavelength
- The shorter the wavelength the higher the intensity of the radiation = more energy
Depends on temperature
- Sun is hot enough to emit short-wave radiation
- All objects on earth emit long-wave radiation
Black-body radiation:
Can radiate and absorb at all wavelengths.
What determines the peak?
- Wien's law λmax= 2898/T in nm
4
- Stefan-Bolzmann law E=εσT
ε = 1 for black body radiation (meaning: it will emit and absorb all the wavelengths), and σ is
the Stefan-Boltzmann constant 5,67*10^8
Types of radiation:
Short-wave radiation
- Can be reflected according to the albedo of an object
- Emitted by the sun (reflected by clouds and surface) (absorbed by atmosphere, biosphere
and surface biosphere will heat up)
Long-wave radiation
- Emitted by surface, because every object that has a certain T emit radiation
- GHG absorbs energy and re-emits it in all directions, but most energy is re-emitted to
surface
Atmosphere will also re-emit long-wave radiation
Temperature troposphere decreasing by height, so emitted radiation is lower when
we get higher in the atmosphere.
,Incoming energy
o Reflection
Albedo (=weerkaatsingsvermogen, percentage of short-wave radiation reflected) (only with
short-wave radiation) (goes in and out as short-wave).
o Scattering
Insolation will be scattered by aerosols in the atmosphere, part will be scattered out of the
atmosphere (only short-wave radiation) (goes in and out as short-wave).
o Absorption
Both long-wave and short-wave radiation
o Re-emission
Both long-wave and short-wave radiation
Energy fluxes: in and out are (almost) equal
Energy lost= long-wave radiation lost + sensible heat lost + latent heat lost
Spatial variability in absorbed shortwave radiation:
more absorption (of shortwave radiation) over tropical areas due to angle of the sun
more absorption over oceans than over land due to
The Earth receives shortwave radiation from the sun. Part of this
radiation is reflected (by objects with high albedo) or scattered back
into space
Another part of solar radiation is absorbed by the atmosphere and the
surface, leading to increased temperatures, and is re-radiated as
longwave radiation.
The atmosphere can absorb part of the radiation from the Earth and re-
radiates this in all directions, parly back to Earth (greenhouse effect)
Besides longwave radiation, the Earth's surface can lose energy through
sensible heat and latent heat (evaporation), depending on moisture
availability
,Lecture 2 – Energy and circulation in the atmosphere
Energy and circulation
Net radiation graph: the tropics are not only heating up and poles cooling down, because energy is
being distributed over the earth. (ocean flows and atmosphere flows)
Forces can lead to acceleration, deceleration or deflection (change in path) according to Newton’s
law: F = m a
Forces are vectors (having magnitude and direction).
Vertical forces on air parcels: pressure is pulling up, but gravity is pulling down
Isopleths= (horizontal) curves along where a specific variable is constant. It is the steepest where
lines are most narrow. The higher in the mountains you are, the lower the pressure.
Isobars= used for atmospheric flows
The pressure gradient force points from high to low pressure .
Coriolis effect
- Because of Earth’s rotation, air parcels moving in the atmosphere
appear to be deflected (change in direction) by Coriolis force
- Flows on the northern hemisphere deflect to right. Southern to left.
F = 2 Ω V sin(φ)
Ω: rotational speed of the earth (constant)
V: wind speed
φ: degree latitude
Coriolis force depends on latitude. The force increases from tropics 0 to poles 90.
Friction
- Close to the surface the air experiences a friction force
- Friction is stronger over land than ocean, because of rougher surface
- Wind speed decreases > Coriolis force decreases
- Pressure gradient remains constant > wind speed not parallel to isobars
(Pressure force, Coriolis force, friction force for horizontal exchange, gravity is vertical)
Due to the pressure gradient force, air moves from areas with high
pressure to low pressure (although the actual path is affected also by the
Coriolis force and friction)
What causes differences in pressure? Unequal heating of the earth’s surface.
Large-scale circulation patterns
Simplified global circulation:
- Air is heated in the tropics and reduces density.
- Tropical air will ascend and move towards the poles.
Due to Coriolis force, the movement towards the poles break up in cells.
(AK samenvatting)
, Wind directions
- Easterly (westward) tradewinds in tropical zone
- Westerlies (eastward flows) in temperate regions
When air is heated, density decreases and air rises. During ascent air cools, leading to condensation
and precipitation.
At higher altitude flow is deflected, air cools and finally subsides leading to high pressure fields near
surface.
Climate zones
- Global circulation patterns have large influence on location of precipitation
- This results in distribution of rain forests and deserts.
El Niño Southern Oscillation (ENSO)
Red= warm than normal
Blue= cooler than normal
Leads to circulation changes in atmosphere.
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