Natural processes GSS summary (lectures and some parts of the book)
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Course
GEO1 2412 Natural Processes
Institution
Universiteit Utrecht (UU)
This document contains all 11 lectures of the course Natural Processes from the GSS program. It also contains some readings (not all of them) and some notes on the Q&A sessions
Lecture 1 Energy in the atmosphere (15/11/2023)
The earth’s atmosphere consists of layers and is relatively thin compared to the earth radius.
- The troposphere consist of 90% of the total mass
- Weather occurs in the troposphere
- The stratosphere contains the protective ozone layer
Dry air consists of several elements
- Nitrogen (78%)
- Oxygen (20%)
- Argon, Carbon dioxide, Neon, Helium, Methane, Krypton and Hydrogen (2%)
There exist different forms of energy
- Kinetic energy
- Potential energy
- Heat energy
- Chemical energy
- Radiation energy
Radiation
- The higher the wavelength, the lower the energy (wavelength is a key parameter for
characterizing different types of radiation)
- Black body radiation: an object that absorbs all radiation falling on it, at all wavelengths. It
also emits radiation in a range of wavelengths according to Planck’s curve
Wien’s Law
- Wavelength where the curve peaks depends on the
temperature of the radiating object
2898
- Formula: ℷ max ¿
T
Stefan-Boltzman Law
- Total emitted energy increases with the temperature
(to the fourth power)
- Formula: E=ε σ T 4, where emissivity ε = 1 for
black body radiation and σ is the Stefan-Boltzmann constant
Short and longwave radiation
- Shortwave radiation: radiation of solar origin, which is primarily in the visible and
has shorter wavelengths. The shortwave radiation rate depends on reflection,
scattering, absorption and re-emission.
- Longwave radiation: the electromagnetic energy that is radiated outward by the
earth (land and sea) at a rate depending on the absolute temperature of the local
surface
- Scattering: similar to reflection (no absorption) but done by aerosols in all directions
- The hotter the object, the shorter the wavelength
Albedo effect
- An expression of the ability of surfaces to reflect sunlight.
- Light colored surfaces return a large part of the sunrays back to the atmosphere
(high albedo), whereas dark surfaces absorb the rays from the sun (low albedo)
- Another part of solar radiation is absorbed by the atmosphere and the surface,
leading to increased temperatures re-radiated as longwave radiation
- Greenhouse effect: the atmosphere can absorb part of the radiation from the earth
and re-radiates this in all directions (partly back to earth)
, Lateral energy transfer
- Transfer through sensible heat, latent heat and oceans
- Latent heat: the heat required to convert a solid into a liquid or a liquid into a vapor,
without changing the temperature (to overcome the intermolecular forces to trigger
a. phase change) evaporation
- Sensible heat: the energy that is needed to raise the temperature of a substance
Desert
- Desert heats and cools more quickly than oceans, since the air contains less
moisture. This means that the air is able to heat up and cool off much more quickly
than air with moisture.
Lecture 2 Energy and circulation in the atmosphere (15/11/2023)
- Since the incoming radiation > outgoing radiation, tropics tend to heat up. For poles
its vice versa (outgoing > incoming)
Forces
- F=M*A
- F = force
- M = mass
- A = acceleration
- Forces are vectors magnitude and
direction can be added
Isopleths (contour lines)
- Curves along which a specific
variable is constant
- For a map of mountains, the steepest part can be recognized at the part where the
contour lines are the most closely spaced
Isobars
- Connect points with the same air pressure in hectopascals (weight per square area of
air above)
- 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 by the Coriolis force
- Flows on the northern hemisphere are deflected to the right and on the southern
hemisphere to the left
- Formula: F = 2ΩV sin (φ )
- Ω = rotational speed of the earth (constant)
- V = wind speed
- φ = degree latitude
- Earths rotational effect on horizontally and freely moving object are greatest at the
poles, therefore the Coriolis effect is the greatest at the poles
- Pressure gradient + wind speed = Coriolis force
Friction
- Close to the surface, the air experiences a friction force (force that resists the sliding
or rolling of one solid object over another)
- Friction is stronger over land than over ocean, because of the rougher surface
Global circulation
, - Air is heated up in the tropics and then reduces its density. The tropical air will
ascend and move towards the poles
- Because of the Coriolis force, the poleward air movement is broken up in different
cells
- Hadley cell = driven by heating in the tropics
- Polar cell = driven by descent of cool air
- Ferrel cell = resulting from circulation in polar and Hadley cells
Convergence and divergence
- When air is heated density decreases
air rises. During the rise of the air, the air cools
which leads to condensation precipitation
- At higher altitude, the flow is deflected
air cools and finally subsides leading to high
pressure fields near the surface
El nino
- In normal conditions the air over the ocean
will move westward (trade winds)
- During el nino conditions, the ocean water is
warmer resulting in upward movement closer t
to South America
- Warmer ocean ocean water flows eastward warmer in the eastside
- El nino shifts circulation and precipitation patterns leads to dry and wet areas
(fires and floods)
- Years with large el nino result in more CO2
1. Warmer water absorbs less CO2
2. Fires result in more CO2
3. Less precipitation leads to plants not being able to do photosensytis
Lecture 3 Moisture in the atmosphere (22/11/2023)
Clausisus-claypeyron relation
- Air can hold more water when it is warmer
- Relative humidity: the amount of water relative
to total amount of water at saturation (%)
- Example if the temperature of the air is 20 C the air
can hold onto 20 Pha water vapor if the air holds 10
Pha of water vapor, the relative humidity is 50%
- This rate will lower when you heat up a bubble of air
without changing its moisture
- Vapor pressure: concentration of water in a certain
volume
- Below the line the air can hold the water vapor
- Above the line the air cannot hold the water vapor,
which leads to precipitation (saturation point)
Convection
- Warm air has a lower density than cold air and rises the air reaches lower
pressures air expands and cools
, Dry adiabatic lapse rate (DALR) yellow
- The rate at which the temperature of a parcel of dry air decreases as the parcel is
lifted in the atmosphere
- It is 9.8 C/km a bubble of air cools down 9.8 degrees if you move it up 1 km
Environmental lapse rate (ELR) green
- The rate at which the air temperature changes
with height in the atmosphere surrounding a cloud
or a rising parcel of air
- Average ELR is 6.4 C/km
Saturated adiabatic lapse rate (SALR)
- Rising air cools down condensation
- Condensation leads to heat release change in
lapse rate SALR
- SALR depends on temperature and moisture in the
air
- SALR < DALR ( as heat is added)
- Average SALR is 6 C/km
Atmospheric stability
- Unstable ELR > DALR
- Stable ELR < SALR
- Conditionally unstable SALR < ELR < DALR
Hydrological cycle
- Evaporation (physical process) : type of vaporization that occurs on the surface of a
liquid as it changes into the gas phase. If the air is saturated there is no evaporation.
Wind can replace wet air with dry air
- Transpiration (biological process) : the process of water movement through a plant
and its evaporation from aerial parts such as, leaves, stems and flowers. Water is
being uptake from the roots, through the trunk water and CO2 diffuses through
openings in leaf (stomates).
- Plants can (partly) close stomates to avoid excessive water loss (during droughts)
- Together evapotranspiration: the sum of all processes by which water moves
from the land surface to the atmosphere
- Potentional evapotranspiration (PET): the maximum water fluc that can be taken up
by the atmosphere. It depends on temperature and humidity of the air. Warm and
dry air can take up a lot of water
- Actual evapotranspiration (AET): depends on soil moisture availability
Moisture budget
- ∆ S=sources−sinks= ( P+ I )−(ET + R+ D)
- S = storage on land
- P = precipitation
- I = irrigation water
- ET = evapotranspiration
- R = runoff
- D = drainage
Precipitation
- Most intense in tropics and over oceans
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