RAMAS 2004-2005
Earth-System Science Techniques
Guide:
Elgered Gunnar
kge@oso.chalmers.se
Names:
Billade Bhushan
Lagadrillière Pierre-Alexis
Moya Espinosa Alain-Michael
Rizwana Begum
Vaquero Maria-Jose
bhusman@student.chalmers.se
pierreal@student.chalmers.se
moyaespi@dd.chalmers.se
begum@student.chalmers.se
vaqueroh@student.chalmers.se
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I.Introduction:....................................................................................................................5
II.Atmosphere History:.......................................................................................................6
III.Structure and functions of each layer of the atmosphere:..........................................7
III.1.Layers:....................................................................................................................7
III.1.1.Ionosphere:........................................................................................................7
III.1.2.Mesosphere:......................................................................................................9
III.1.3.Stratosphere:.....................................................................................................9
III.1.4.Troposphere:...................................................................................................11
III.2.Winds:..................................................................................................................11
III.2.1.Newton's Law : ..............................................................................................12
III.2.2.Air pressure gradient : ....................................................................................13
III.2.3.Coriolis Effect :...............................................................................................13
III.2.4.Frictional Force...............................................................................................14
III.2.5.Convergent and Divergent Flow.....................................................................14
III.2.6.Global Circulation:..........................................................................................15
III.3.Temperature :......................................................................................................17
III.3.1.Simple model of the decrease of the temperature in the troposphere:............19
III.3.2.Temperature records:......................................................................................19
III.3.3.Simple models of the world’s mean temperatures:.........................................21
IV.Interactions with biosphere, geosphere, and hydrosphere:.......................................22
IV.1.Interaction between atmosphere and biosphere:..............................................22
IV.1.1.Effect of deep rooted vegetation:....................................................................22
IV.1.2.Greenhouse effect:..........................................................................................22
IV.1.3.Effect of pollution:..........................................................................................24
IV.2.Interactions between atmosphere and hydrosphere: ......................................25
IV.2.1.Effect of water vapour:...................................................................................25
IV.2.2.Effect of water, ice caps, sea ice:....................................................................25
IV.2.3.Effect of volcanoes on atmosphere:................................................................26
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IV.3.The Hydrologic cycle:..........................................................................................27
IV.3.1.Water reservoirs:.............................................................................................28
IV.3.2.Pathways:........................................................................................................28
IV.3.3.Anthropologic effects:....................................................................................29
IV.3.4.The energy budget of the atmosphere:............................................................30
V.Measurements techniques:...........................................................................................31
V.1.Measurement of different elements:....................................................................31
V.2.Wind Speed :.........................................................................................................32
V.3.Balloons and rockets:............................................................................................33
VI.References:..................................................................................................................35
VI.1.Bibliography:.......................................................................................................35
VI.2.Internet resources:...............................................................................................35
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I.
Introduction:
In this report, we will describe the most important aspects of the atmosphere. It is
the result of an investigation done in the course Earth Science techniques, in parallel with
investigations on the biosphere, geosphere and hydrosphere made by other groups.
The atmosphere is dated back to about 5 billion years, when the earths interior began
outgasing and forming a primitive atmosphere. The atmosphere evolved from that to a
complex structure of different layers. From the highest , the Ionosphere of about 600 km,,
to the lowest Troposphere, the atmosphere has a specific purpose for the function of all
earth systems. As it interacts with all other spheres earlier mentioned, it gives life the
proper ambient to exist. Temperatures, composition, pressures are described here to give
a rough idea on how the atmosphere works, and also to show that the atmosphere is quite
delicate to our interventions. Finally we also mention some about the techniques used for
measuring different parameters.
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II.
Atmosphere History:
Earth was believed to be formed about 5 billion years ago. At that time, it was just
a hot body of lava, gases present that time were mainly hydrogen and helium. Over the
time, temperature decreased and earth'
s crust was formed, containing hot lava
underneaths, which resulted into volcanic activity. During first 500 million years, dense
atmosphere was formed because of the volcanic activity and degassing from interior of
earth. This atmosphere was retained because of earth's
gravity. The early atmosphere was
mostly dominated by carbon dioxide, and other gases like H2, water vapor, CH4 and N2.
Atmosphere of the Venus is a good example of earth'
s atmosphere at that time. Around
after 1 billion years hydrosphere was formed because of the condensation of water vapor,
rain began to fill low areas forming first ocean. In ancient environment there was no free
oxygen, as evidenced by ancient rocks that contained elements such as Iron, Uranium in
their reduced states. Around about one billion year ago, aquatic micro organisms were
formed. These micro organisms called blue­green algae or Cyano­bacteria started using
energy from the sun light to split molecules of H2O and CO2 and recombine them into
organic compound and Oxygen this was the First Photosynthesis process. Some of the
oxygen recombined with metals and carbon forming their oxides and some oxygen
remain in atmosphere. Over the time oxygen in atmosphere increased and CO2 decreased.
In higher part of atmosphere, some oxygen molecules, after interacting with UV
rays of sun light, split up into single oxygen atoms. These single atoms combined with O2
and formed ozone layer in upper atmosphere. Ozone layer is believed to have in existence
since 600 million years. Prior to this life was restricted to Oceans only. Presence of
Ozone layer helped the organism to develop their life on land. ( Ref: II )
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III.
Structure and functions of each layer of the
atmosphere:
III.1. Layers:
The atmosphere changes from the ground up and four distinct layers have been
identified depending on the temperature changes, chemical composition, movement,
density, and ionization.
The following figure shows the different layers of the atmosphere:
Jet streams
Figure 1: The 4 layers of the atmosphere ( Ref: III.1)
Above all these layers, there is the exosphere which starts at the top of the
ionosphere and continues until it merges with interplanetary gases, or space. In this
region of the atmosphere, Hydrogen and Helium are the prime components and are only
present at extremely low densities.
III.1.1.
Ionosphere:
The ionosphere is known as the upper atmosphere and it extends 600 kilometers.
The temperatures go up as you increase in altitude due to the Sun's energy. Temperatures
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in this region can go as high as 1727 ºC. Chemical reactions occur much faster here than
on the surface of the Earth.
The existence of charged particles signals the beginning of the ionosphere a region
compiling the properties of gas and plasma. The structure of the ionosphere is strongly
influenced by the charged particle wind from the Sun (Solar wind), which is in turn
governed by the level of Solar activity. One measure of the structure of the ionosphere is
the free electron density, which is an indicator of the degree of ionization.
The solar radiation strikes the atmosphere with a power density of 1370 Watts per
2
meter or 0.137 Watts per cm2, a value known as the "solar constant". This intense level
of radiation is spread over a broad spectrum ranging from radio frequencies through
infrared (IR) radiation and visible light to X-rays. Solar radiation at ultraviolet (UV) and
shorter wavelengths are considered to be "ionizing" since photons of energy at these
frequencies are capable of dislodging an electron from a neutral gas atom or molecule
during a collision. The conceptual drawing below is a simplified explanation of this
process.
Figure 2: The solar ionization ( Ref: III.1.1)
Incoming solar radiation is incident on a gas atom (or molecule). In the process, a
part of this radiation is absorbed by the atom, and a free electron and a positively charged
ion are produced. Cosmic rays and solar wind particles also play a role in this process but
their effect is minor compared to that due to the sun's electromagnetic radiation.
At the highest levels of the Earth's outer atmosphere, solar radiation is very strong
but there are few atoms to interact with. So, ionization is small. As the altitude decreases,
more gas atoms are present so that the ionization process increases. However, at the same
time, an opposing process called recombination begins to take place, in which a free
electron is "captured" by a positive ion if it moves close enough to it. As the gas density
increases at lower altitudes, the recombination process accelerates since the gas
molecules and ions are closer together. The point of balance between these two processes
determines the degree of "ionization" present at any given time.
At still lower altitudes, the number of gas atoms (and molecules) increases further
and there are more opportunities to absorb the energy from a photon of UV solar
radiation. However, the intensity of this radiation is smaller at these lower altitudes
because some of it was absorbed at the higher levels.
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III.1.2.
Mesosphere:
The mesosphere is the third highest layer in the atmosphere, occupying the region
between 50 km and 80 km above the surface of the Earth, above the troposphere and
stratosphere, and below the ionosphere. It is separated from the stratosphere by the
stratopause and from the thermosphere by the mesopause. The chemicals are in an excited
state, as they absorb energy from the Sun.
Temperatures in the mesosphere drop with increasing altitude to about -100°C.
The mesosphere is the coldest of the atmospheric layers. In fact, it is colder than
Antarctica's lowest recorded temperature. It is cold enough to freeze water vapor into ice
clouds. You can see these clouds if sunlight hits them after sunset. They are called
Noctilucent Clouds (NLC). NLCs are most readily visible when the Sun is from 4 to 16
degrees below the horizon.
The mesosphere is also the layer in which a lot of meteors burn up while entering
the Earth's atmosphere. From the Earth, they are seen as shooting stars.
The layer which separate the mesosphere from the ionosphere is the mesopause.
III.1.3.
Stratosphere:
The stratosphere is characterized by a slight temperature increase with altitude,
the temperature in this region increases gradually to –3 ºC, due to the absorption of
ultraviolet radiation. This layer is also characterized by the absence of clouds. Only the
highest clouds (cirrus, cirrostratus, and cirrocumulus) are in the lower stratosphere.
The stratosphere extends between 17 to 50 kilometers above the earth's surface.
This part of the atmosphere is dry and less dense compared to the troposphere (the layer
below the stratosphere).
In this layer is located the ozone layer . Ozone, a form of oxygen, is crucial to our
survival, because this layer absorbs a lot of ultraviolet solar energy.
The stratopause is the layer that separates the stratosphere from the mesosphere.
Ozone layer:
The Ozone layer is a layer in the stratosphere which protects the Earth from the
harmful effects of ultra-violet radiation from space. Discussion about the Ozone Layer
became popular when, in 1984, it was discovered that above Antarctica, there was a hole
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in the layer. This was not expected and started scientists on a search to discover why the
hole had appeared, and what had caused it.
The use of chlorofluorocarbons ( cfc's ) in products that discharged them into the
atmosphere have caused serious damage to the Ozone layer.
In October 1987, scientists were surprised again when the hole over Antarctica
reached the same size as the USA.
However, there is a long delay between cfc's being released into the air, and their
arrival in the stratosphere. It can take ten years for the gasses to reach the stratosphere,
and another one hundred years before they are naturally destroyed. This means that we
may have to live with the consequences of past pollution for many years to come.
Apart from cfc's, which are now used far less frequently in the developed world
than they used to be, two other 'greenhouse' gasses have a bad effect on ozone. These are
nitrous oxide and methane. Nitrous Oxide breaks down and destroys ozone as it goes, and
methane actually creates more ozone, but in the wrong part of the atmosphere. The
methane generates more ozone in the tropopause, which is below the stratosphere, and
this layer can hide the holes in the stratosphere above it.
The main importance of ozone is that it acts like a sunblock, filtering out the
dangerous ultra-violet rays from the sun. Humans and animals exposed to excessive UV
light can develop cancers, their skin ages more quickly and their immune systems are
reduced.
Crops also seem to be damaged by extra UV. Some forms of Soya bean, an
increasingly important crop, have suffered a 25 percent decrease in yield when their
exposure to UV B rays was increased by 25 percent.
In the seas, it has been found that phytoplankton, the foundation of the ocean food
chain, are vulnerable to high exposure to UV rays, as are some fish larvae. Since the
human population acquires much of this food ( especially protein from fish) from the
oceans, damage to the phytoplankton might result in a massive reduction in fish stocks
and the loss of an important source of food for us.
Finally, and possibly the most worrying is the possibility that in the future, the
ozone layer will start to let very harmful UV- C rays reach the surface of the Earth. At the
moment the layer stops all UV- C before reaching us. We know that UV-C can alter and
destroy DNA and proteins. We can only guess at the consequences for the human race if
our DNA is exposed to UV- C for long periods.
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III.1.4.
Troposphere:
The troposphere starts at the Earth's surface and it extends 8 to 14.5 kilometers
high. This part of the atmosphere is the most dense. As you climb higher in this layer, the
temperature drops from about 17 ºC at sea level to –52 ºC at the beginning of the
tropopause. The primary gases we can find in this region are nitrogen and oxygen. The
troposphere contains over 75 percent of all the atmosphere's gases and vast quantities of
water and dust. As the sun heats the ground, it keeps this thick mixture churning. The
weather is caused by these churnings of the mass. The troposphere is the layer in which
all which we call "weather" occurs. The troposphere is normally warmest at ground level
and cools higher up where it reaches its upper boundary (the tropopause).
The tropopause is the layer which separate the troposphere from the stratosphere.
It varies in height. At the equator it is at 8 km high, at 50 N and 50 S, 9 km and at the
poles 6 km high.
III.2. Winds:
Wind is the result of movement of air due to difference in pressure. It is the result of
flow of air from high pressure area to low pressure area, to eliminate pressure difference.
Pressure that's higher at one place than another sets up a force pushing air from the high
pressure area toward the low pressure area. Greater the difference in pressures, stronger
the force. Distance between high pressure and low pressure area determines how fast the
moving air is accelerated.
Figure 3: Movements of air due to the difference in pressure( Ref: III.2a )
In the horizontal direction, pressure can change by about 10 mb in a distance of
100's of kilometers, whereas in the vertical direction, the pressure changes by almost
1000 mb in about 10-12 km. Yet, it is the horizontal variation of pressure that generates
our winds.
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Figure 4: Model of an air column warming ( Ref: III.2b )
Air can approximately be regarded as an “Ideal Gas" which obey the "Ideal gas
law" P = C * ρ * T . So the factors affecting air pressure are Density(ρ) and
Temperature(T). If temperature is constant, then P will increase by increasing the density
of the gas. If we take a air column and increase the temperature and let the gas expand so
that the column with warm air occupies more volume, then we observe that both air
column will have same pressure. (Ref: III.2 )
III.2.1.
Newton's Law :
If we apply Newton's Law to an air parcel, then the force acting on this air parcel
can be obtained from the equation :
F= m * a
where:
F = force (a push or pull)
m = mass of the object (parcel)
a = the resultant acceleration (speed up or slow down)
If there is only one force, the net acceleration of the wind will be :
anet = F1 / m
However, if there are many forces involved, the net acceleration will be:
anet = ( F1 + F2 + F3 + F4 ... + Fn ) / m
(where ‘a’ & ‘F’ are vectors)
If we consider that earth is not rotating and does not have any friction with wind,
then wind will flow in a straight line and would flow longer and harder than it does. But
the forces in above equation must be taken into account.
Some of the Forces affecting wind and its speed / acceleration can be listed as:
1. Air pressure gradient;
2. Coriolis effect;
3. Friction.
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III.2.2.
Air pressure gradient :
Pressure gradient can be defined as a change in pressure over a given distance,
i.e.,
Pressure Gradient = ?P / Distance = ( Phigh – PLow ) / Distance
Air pressure gradient is determined by Isobar on weather map. An isobar on a
weather map is a line where the air has the same pressure all along the line.
Figure 5 : Examples of pressure gradient in Europe ( Ref: Blue)
Spacing between isobar determines pressure gradient, closer isobar represents
steep gradient whereas more spacing between isobar represents low pressure gradient.
Between the steep pressure gradient air flows rapidly resulting in high speed wind. ( Ref:
III.2 )
III.2.3.
Coriolis Effect :
Coriolis effect is an inertial force described by the 19th-century French engineermathematician Gustave-Gaspard Coriolis. If we consider an ordinary body in motion, in a
rotating frame of reference, an inertial force acts to the right of the direction of body
motion for counterclockwise rotation of the reference frame or to the left for clockwise
rotation. The effect of the Coriolis force is an apparent deflection of the path of an object
that moves within a rotating coordinate system. The object does not actually deviate from
its path, but it appears to do so because of the motion of the coordinate system.
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Figure 6 : The Coriolis deflection and its effect on the wind ( Ref: III.2.1 )
Because of this force winds in northern hemisphere bends to right side and in
southern hemisphere to the left side. The coriolis force is proportional to the wind speed,
that means if the speed of wind is more we will observe more bending of wind from its
normal path.
III.2.4.
Frictional Force
When wind flows near the surface of earth friction from trees, solid objects slows
its speed. As magnitude of coriolis force is proportional to the speed, decrease in wind
speed also decreases coriolis force, causing northern hemisphere wind to turn a little to
left and southern hemisphere wind to right.
Winds in the higher atmosphere does not have effect of friction. So, whenever
pressure gradient increases, wind starts flowing in the perpendicular direction to isobar,
steeper the gradient greater the wind speed. Once the wind flow starts, coriolis effect
comes in the picture bending the wind direction. Wind direction is no longer
perpendicular to isobar but now with some oblique angle. When the pressure gradient
flow and coriolis deflection are in balance, the wind flows parallel to the isobar.
III.2.5.
Convergent and Divergent Flow
In low pressure winds will flow inward from all the direction, and these wind are
affected by coriolis deflection, as a result wind around center develop an inward spiral
motion called Cyclone, in high pressure area wind flows spirally outward this motion is
called Anticyclone. In northern hemisphere the inward flowing low pressure spiral rotates
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in clockwise direction and outward spiral in counterclockwise. In southern hemisphere it
is exactly reverse.
Figure 7 : Cyclone and Anticyclone ( Ref: Blue)
As air from high pressure area is going out in all directions in the Anticyclone, it
causes divergence which draws air from high altitude to center, resulting drop in relative
humidity and leading to clear, cloudless sky. Whereas in low pressure area incoming
wind causes convergence which lead to an upward flow of air, resulting in cloud cover
and rain.
Figure 8 : Convergent and divergent flows ( Ref: Blue)
III.2.6.
Global Circulation:
The circulation of air over the earth is largely due to the unequal heating of the
earth surface due to solar radiation. The global circulation of pressure and wind plays an
integral role in the heat balance of the earth. Global circulation of air in the atmosphere
transfers warm air from low latitudes towards high latitudes, and cold air from high
latitudes towards low latitudes.
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Figure 9 : The circulation of air around the Earth ( Ref: III.2.2 )
At the equator direct rays from Sun heats the air, raising air to the upper part of
atmosphere, leaving low pressure areas behind. In the upper part, air diverges and moves
towards polar area, again because of coriolis force air turns eastwards, clearly this wind
can not reach pole. And so air tend to pile up at 30N and 30S creating two belt of high
pressure air around the world, the Hadley Cell. Air in this belt begins to cool and sink.
Between thirty degrees latitude and the equator, most of the cooling sinking air moves
back to the equator. The air movements toward the equator are called trade winds.
At the pole, cold dense air descends, causing an area of subsidence and high
pressure. As the air sinks, it begins spreading southward. Since the effect of coriolis force
in polar area is strong, the southward moving air deflects sharply to the right. This wind
is called the surface polar easterlies, although the upper winds are still predominantly
from the southwest. Near 60ºN, the south-easterly moving air moving along the surface
collides with the weak, north-westerly surface flow that resulted from spreading air at 30°
N. This colliding air rises, creating a belt of low pressure near 60°N.
Figure 10 : Description of the air and winds circulation ( Ref: III.2.2 )
The mid-latitude circulation cell between the Polar cell and the Hadley cell is
called the Ferrel cell. The Ferrel cell circulation is somewhat complex compared with
Hadley and Polar cells. It is believed that the cell is a forced phenomena, induced by
interaction between the other two cells. The stronger downward vertical motion and
surface convergence at 30°N coupled with surface convergence and net upward vertical
motion at 60°N induces the circulation of the Ferrel cell. This net circulation pattern is
greatly upset by the exchange of polar air moving southward and tropical air moving
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northward. This explains why the mid-latitudes experience the widest range of weather
types.
Figure 11 : Formation of the Jet streams ( Ref: III.2.3 )
One more important flow of wind/air is Jet Stream, jet stream is flow of fast
moving air in the upper path of the atmosphere around 10 Km high. Jet stream is formed
because of the difference in temperature of two air masses. Jet stream flows between the
boundaries of such air masses. The speed of jet stream depend on the difference in
temperature between two air masses, higher the difference more the speed. Jet stream are
usually formed in winter when there is a large difference in temperature between air at
high latitude and at low latitude. Sometimes wind speed can exceed 200 Km/h.
III.3. Temperature :
The temperature is a really important parameter to describe the world. Even if we
can’t see it, we can feel it and see what happen with its fluctuations. For example,
according to this temperature, it can rain or snow. As a consequence, it is one of the
quantities characterising the behaviour of the atmosphere, and especially the troposphere
with the weather. But it is also a parameter which depends on a lot of others like the place
where you measure it, the season, etc. However, scientists have defined an average
Earth’s temperature (at the surface): ~13°C. But in every place, the temperature can be
different. This is due to:
• Exposition to the sun;
Figure 12 : Sun exposition, where area(A) < area(B), which implies that the temperature at A is
higher than at B
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•
•
•
•
Altitude;
Weather;
Seasons;
...
Figure 13 : Temperature trends by 5º latitude bands (where data are available) in three different data
sets: observed surface data ( = ST ), derived surface data ( = R2–2m ), satellite-based lower tropospheric
data ( = MSU ). All of these data are for the most part independent of one another. Notice how the
trends from the derived surface data more closely match trends from satellite data than they do observed
surface data. ( Ref: III.3.1 )
Nowadays, we have to take care about it because this average temperature has
increased for a few decades from about 1°C. This value seems to be so small, but this
could really have bad consequences, especially because it appears that temperature
continues to increase. In fact, this could warm water and make the sea growing up (ice on
the poles which would melt), modify the water cycle, etc.
Figure 14 : Global average temperatures 1860-2002 (difference from 1961-1990 normals, °C), using air
measurements at land stations and sea surface temperatures measured by ships and buoys. ( Ref:
III.3.2 )
The variations of temperature causes atmospheric circulation. In fact, when the air
is heated (especially near the equator, where the sun heats more), it expands and the density is lower (like most of the gases). It results that the air rises, and flows in the upper atmosphere towards both poles. Here(at the poles), it becomes colder, and begins to sink
back, where it flows along the surface and comes back to the equator.
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Figure 15 : Simple circulation of air ( Ref: III.3.3 )
III.3.1.
Simple model of the decrease of the temperature in the
troposphere:
The temperature decreases with the height due to expansion.
If we assume a dry air parcel with no exchange of heat with its surroundings (adiabatic),
then we obtain a “lapse-rate” Γ, so that:
– Γ = dT / dZ = – 9.8 K.km –1
Note: In moist air, we have: Γ = 6 K.km –1
III.3.2.
Temperature records:
As we can see in the different temperature profiles below, the mean temperature is
related to the composition of the troposphere, and especially to the concentration in
carbon dioxide.
How can we obtain such profiles? Different techniques are used to estimate past
temperatures, using for example corals, ice cores, tree rings, and more recently
instruments like thermometers and satellites.
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Figure 16 : Temperature records since 450 000 years ( Ref: III.3.4 )
Figure 17 : Temperatures records since 1 000 years ( Ref: III.3.4 )
These profile show us that there were a lot of variations in temperature since the
last 450000 years. All these fluctuations seem to come from two different things:
o Solar activity;
o Variations in the Earth’s orbit. In fact, when the orbit changes, there are
variations of energy coming from the Sun to the Earth. And this lead to
variations in production of CO2 from the oceans and the biosphere. That can
explain, with the process of greenhouse effect, why the temperatures are
changing like above.
We can also observe that compared with the temperatures until 450000 years, the
actual temperatures seem to be normal. But compared to the temperatures until 1000
years before, we see that there was an increase of the temperature, and especially during
the last century.
Thereby, does it come from the industrialisation?
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III.3.3.
Simple models of the world’s mean temperatures:
Here are 2 simple models of the world with the mean temperatures for July and January:
Figure 18 : Mean temperature for January ( Ref: III.3.5 )
Figure 19 : Mean world temperature for July ( Ref: III.3.5 )
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IV.
Interactions with biosphere, geosphere, and
hydrosphere:
IV.1. Interaction between atmosphere and biosphere:
IV.1.1.
Effect of deep rooted vegetation:
Figure 20 shows the effect of deep rooted vegetation on the atmosphere.
Deep roots provide an increase in soil water storage capacity which in turn
increases the access to water stored in the soil for dry periods. Because of this,
transpiration is enhanced during the dry season which leads to local cooling and
moister air. In this way, more moisture is transferred to the inner tropical convergence
zone which results in precipitation. The shaded areas in the fig 20 denote water.
Figure 20 : Effect of deep rooted vegetation on the atmosphere ( Ref: IV.1)
The depth of the root system controls the maximum amount of soil water that can
be transpired by the vegetation into the atmosphere during dry periods. Water uptake
from deep soil layers has been found to contribute significantly to the dry season
transpiration at some sites in Amazonia and it has been estimated that large parts of the
evergreen forests in Amazonia depend on deep roots to survive the dry season. Thus, the
presence of deep roots will provide a significant source of atmospheric moisture during
the dry season.
IV.1.2.
Greenhouse effect:
Carbon dioxide is the most important anthropogenic greenhouse gas contributing
60%.the atmospheric concentration of carbon dioxide has increased by almost one third
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from 280 ppm to 370 ppm in 2002. The reasons are due to the emissions produced by the
burning of fossil fuels, due to burning of forests most of the CO2 present in the
vegetation is burnt,due to increase in soil erosion.Measurements shows that the
atmospheric carbon dioxide content has increases by 3.2 Gt C per year .The ocean and
the land biosphere are the most important carbon sinks.they are interacting with
atmosphere.Atmospheric CO2 is exchanged with the ocean and the land ecosystem.
Figure 21: Atmospheric CO2 concentrations 900-2000; box:
CO2 emissions growth rate of atmospheric concentration
1958-1998 ( Ref: IV.2 )
Figure 22: ( Ref: IV .2 )
The total amount of CO2 dissolved in the ocean is about 20 times greater than the
terrestrial CO2 amount and 50 times higher than the atmospheric CO2 amount. The CO2
exchange is a dissolution and outgassing process of carbon dioxide into and from the
surface layer of the ocean , and is regulated via the CO2 partial pressure difference
between air and water. This exchangeleads to total of approx 90 Gt C per year which
leads to compensation between the CO2 content of the atmosphere and the surface water.
The land biosphere exchanges carbon dioxide with the atmosphere through
photosynthesis, respiration and bacterial decomposition.
The balance of exchanges with the atmosphere can be positive depending on the intensity
of the processes released or absorbed carbon.In this case, the biosphere is a source of
carbon dioxide for the atmosphere. Alternatively, the balance may be negative, in which
case the terrestrial biosphere acts as a carbon dioxide sink.
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Figure 23: The Carbon cycle. ( Ref: IV.2 )
IV.1.3.
Effect of pollution:
Humans are generating pollution.there are different types of pollution caused by
people like air pollution,water pollution.but the air pollution will effect the atmosphere
alot.this can be caused due to automobiles which in turn causes rain full of toxic
chemicals.the incomplete combustion of fuels results in large quantity of sulphur.this
sulphur combines with oxygen to form sulphurdioxide,which in turn combines with
water droplets and form sulphuric acid or acid rain.the incomplete combustion of fossils
fuel releases carbondioxide which causes green house effect.
Air pollution also effects statosphere,the ozone layer.ozone absorbs the
shortwaveultravoilet radiation from the sun.Pollutant concentrates are reduced by
atmospheric mixing, which depends on such weather conditions as temperature, wind
speed, and the movement of high and low pressure systems and their interaction with the
local topography. But sometimes a condition called an inversion occurs, in which a cold
layer of air settles under a warm layer. This prevents an upward movement of air,
atmospheric mixing is retarded and pollutants are trapped near the ground.
Figure 24: Air Pollution caused from heavy industry ( Ref: IV.4 )
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IV.2. Interactions between atmosphere and hydrosphere:
IV.2.1.
Effect of water vapour:
The water vapour in the atmosphere is essentially molecules of steam evaporated water - bounding around very thinly diluted among the gaseous nitrogen and
oxygen molecules that make up the atmosphere. This water vapor can be experienced as
humidity.
Water vapour plays a critical role in affecting both climate and weather. The amount of
water vapor in the atmosphere is not at all uniform ,far from it,but changes drastically and
abruptly, often in a matter of a few hours, to cause, for example, thunderstorms.
Figure 25: Hydrological cycle ( Ref: IV.8 )
It takes a lot of energy to evaporate water. A molecule of water vapor "contains"
much more energy than a molecule of liquid water. water vapor is one of the most
important "storehouses" of energy in the atmosphere and in the climate system.
When water vapor condenses to form clouds, it has another important effect: it "shades"
Earth's surface and lower atmosphere. In the greenhouse analogy, rolling down a shade
over the greenhouse would cool off the interior, just as it would cool a sunny room When
clouds shade the Earth, some of the incoming solar energy is reflected back into space.
Some also is absorbed by the clouds and re-radiated upwards and downwards. Thus some
of the energy is caught at altitudes higher than Earth's surface, but still in the atmosphere.
But water in its vaporous state has an important heat-trapping " explained by water
vapor's being relatively transparent to the shorter wavelengths at the visible and
ultraviolet end of the light spectrum But after this energy has warmed the Earth's surface
and been re-radiated upward in the infrared bands of the spectrum, water vapor readily
absorbs it - trapping heat in the lower atmosphere (troposphere). Thus the water vapor is
like the heat-trapping "glass" in the greenhouse analogy.
IV.2.2.
Effect of water, ice caps, sea ice:
Climate change is a better phrase than global warming because it encompasses
many kinds of effects. Some areas will be warmer, some cooler, sea levels may rise, polar
25
ice caps may melt, deserts might spread across Europe and extreme weather events may
become more frequent. The Intergovernmental Panel on Climate Change estimates that
the global temperature will rise by as much as 6°C this century. near the poles, in parts of
Alaska, Canada, Siberia and the Antarctic, temperatures are rising faster than elsewhere.
The permafrost is melting and plants, animals and the people that live there are already
being affected.
Arctic sea ice is melting at a faster rate than previously thought. . Melting sea ice doesn't
raise sea levels but it could threaten ocean productivity, change current systems and
disrupt global weather .
Sea ice also plays an important role in keeping the ice and snow covering the Antarctic
continent in place. With nothing to stop it, the Antarctic ice sheet may slide into the
ocean and melt.
If the sea rises by half a metre, this number could double. A metre rise would inundate
1% of Egypt's land, 6% of the Netherlands and 17.5% of Bangladesh. Only 20% of the
Marshall Islands would be left above water. Although the ice sheets in Greenland have
been thinning, analysis of long-term climate information (presented in the journal
Geophysical Review Letters) has shown that temperatures in the southern part of the
island and the Labrador Sea have fallen over the last 40 years, not risen.
global climate change shifts temperatures across the planet . According to UNEP,
they will have to migrate 10 times as fast as they did after the last ice age. Many won't
make it. Species that do move will do so at different rates, breaking up existing
communities. At high latitudes, entire forest types are expected to disappear, to be
replaced by new ones. During this transition, carbon will be lost to the atmosphere faster
than it can be replaced by new growth, accelerating climate change. In the high
atmosphere the sulphur dioxide coverts into aerosols which reflect the sun's radiation
back into space and thereby cooling the surface of the Earth.Interactions between
geosphere and atmosphere:
IV.2.3.
Effect of volcanoes on atmosphere:
The volcanic dust was spread around the upper atmosphere by the jetstreams, and
it has been estimated that the world temperature fell by over 1C (2F). The year after,
1816, has been described as the year without a summer.
Volcanoes release large amount of sulphur compounds such as sulfurdioxide. This will
effect the climate more than the dust particles ejected from jetstreams.when this
sulfurdioxide combines with waterdroplets in the air forms sulphuric acid.this sulphuric
acid when falls on earth causes significant cooling.but this has been the primary cause of
the global cooling that occurred after the Pinatubo and Tambora eruptions .
26
Figure 26 : Popocatépetl Volcano near Mexico
City, Mexico ( Ref: IV.6 )
Figure 27 : Effects of volcanoes ( Ref: IV.6 )
Volcanoes releases large amount of carbondioxide and water. these two
compounds will be in the form of gases in the atmosphere, they absorb heat radiation
emitted by the ground . This causes the air below to get warmer. But this will not make
the globe warmer.the effect is little.over long periods of time , multiple eruptions of giant
volcanoes, such as the flood basalt volcanoes, can raise the carbon dioxide levels enough
to cause significant global warming.
IV.3. The Hydrologic cycle:
The most familiar cycle is probably the hydrologic cycle, which describes the
fluxes of water between the various reservoirs of the hydrosphere ( Ref: Blue ). It is
important to remember that water is extremely important for all life. It is used by
different systems, biologic, geologic and atmospheric. It is almost never destroyed,
instead it changes state and gets transported. There is fixed amount of water on the planet.
This means that the water you drink is the same water the dinosaurs drank once upon a
time. Therefore, it is essential to know about the hydrologic cycle.
Another important impact of the hydrologic cycle on the earth, is that it shapes the
landscape to great variety. The hydrologic cycle is closely related to the to the cycle of
rocks ( Ref: Blue ).
As we already know, water can exist in the stable states, solid, gaseous and liquid. The
physical state of water is determined by its temperature and pressure. As we identify the
reservoirs of water we need to keep this in mind.
27
Figure 28 : The Hydrologic Cycle ( Ref: Blue )
IV.3.1.
Water reservoirs:
The reservoirs can be divided into ground water, surface water and water in the
atmosphere as clouds and air humidity. Most of the water is of course located to the
oceans which make up for more than 97.5 % of all the water in the system. Meaning that
most of the water is saline, not fresh water. The ice-caps contain 74 % of all fresh water.
The next largest reservoir of unfrozen fresh water is the groundwater, which represents
98.5 % of this unfrozen fresh water. Water resident in lakes and streams actually make up
only a small fraction of the total together with atmospheric humidity. The size of the
reservoir is very important for how long the water resides in the reservoir, known as the
residence time. The bigger the reservoir, the longer the water will reside in the reservoir.
For example, polar ice-caps can contain water for thousands of years, in lakes the
residence time is small in comparison, such as a few weeks to a month. This makes the
polar ice-caps an ideal place to look for information on past atmospheric conditions. The
residence time is important in its turn to know how fast changes can propagate through
the system.
IV.3.2.
Pathways:
The sun is the driving force for the whole system. The hydrological cycle starts
(since its a cycle it actually doesn't start anywhere) when water evaporates from the
surface of the earth, land or sea. Remember that about 70% of the earth most of the
surface is covered by water ( Ref: IV.9 ). On land it also leaves the surface in
transpiration from the pores of plants and even animals. Water vapor in turn forms
28
clouds that contain small water drops. When the drops grow in size and become so heavy
that the gravity pulling them down is much greater than the upward winds, it falls as
precipitation in the different forms. It can fall as rain, hail or snow. In many cases the
precipitation doesn't reach the ground before it evaporates again and return to the clouds.
When it reaches the ground it can infiltrate the soil recharging groundwater reservoirs or
it remains on the surface and fills up lakes and streams. From the surface reservoirs,
water makes its way back to the oceans via so called surface runoff, where the cycle starts
all over again.
Figure 29 : Earth's water reservoirs and fluxes ( Ref: IV.9 )
Water in the atmosphere does not rise that high, it is mostly located to the
troposphere, a thin layer close to the earth. Surprisingly most of our weather occurs in
this thin layer. This means that the atmosphere above the troposphere is quite dry.
IV.3.3.
Anthropologic effects:
The large cultivations made by man influence the amount of water evaporated
through altering the surface of the soil , which otherwise would be covered by wild
vegetation. This vegetation has, of course not the same evaporation characteristics as our
grown vegetation thus changing the evaporation properties of the surfaces.
A good example of this could be the rainforests that are being devastated. This doesn't
only influence the CO2 level of the atmospheres but also the hydrological cycle, by
changing the total amount of forest surface of the earth.
The ices melting due to the greenhouse effect is also causing a change in the
surface of the earth, and affecting the hydro level on the atmosphere. The ice reflects a
great deal of the solar radiation: if it melts, there will be more radiation absorbed,
increasing the humidity in the atmosphere. This is a positive feedback system since the
increased temperature will melt more ice, making it unstable.
29
Human release of particles into the atmosphere increase the ability for water drops
and ice particles to form since they need a solid base to form onto. The increased
formation of clouds works as described before.
IV.3.4.
The energy budget of the atmosphere:
In the atmosphere, energy transport is closely related to the hydrological cycle
since most of the energy is concentrated to the water. Vapor has an great ability to store
heat energy and to release it.
The energy absorbed by the atmosphere comes both from sun radiation and energy
emitted from the surface of the earth. One often measures the energy radiated by the sun
over the average of the surface of the whole earth, making it an average over a time
period evolving both day and night. In figure (See the figure 30 : The energy budget) we
can see that total incident short-wave radiation from the sun is 343 W.m-2. Approximately
30 % of that amount is reflected back to space. Of the remaining, 20 % is absorbed by the
atmosphere. 50 % reached the surface. In it's turn, the surface of the earth emit heat
radiation to the atmosphere in an intricate system of absorption and re-emission to and
from clouds on different levels. Practically, for the clouds the surface of the earth acts as
a heat source and the space acts as a heat sink.
Energy is internally stored in the atmosphere in both thermal and mechanical
form. The thermal form is the temperature of the atmosphere, i.e. the random motion of
molecules. The mechanical energy form, is the potential energy of the atmospheric mass
within the earths gravity, and also in the form of kinetic energy in the motion of air.
These internal forms of energy are responsible for redistribution of energy within the
atmosphere.
Figure 30 : The energy budget [W.m-2 ] ( Ref: Salby )
30
V.
Measurements techniques:
Radar is a technique often used. Doppler reflection from e.g. precipitation for
determining wind speed, direction.
Polarisation of reflected light is used to check the polarization direction of the reflecting
media, it could be sea-waves or ices. This indicates sea-wave directions, and one can also
extract information about the amplitude of the sea-waves, because the reflected lights has
a dependency on the wave height. Through sending a electromagnetic waves with
different amplitudes and wavelengths, and observing the reflected radiation one can
extract information of the reflecting media. Since all matter has its specific spectrum, it is
easy to extract information on the composition of the atmosphere through registering the
spectrum of the received light.
The drawbacks for the reflecting EM-radiation methods is that it is a result of the total
path of the ray. It is not a local value, that sometimes is the interesting parameter.
Sometimes it is an advantage, depending on the application.
Satellite measurement gives a global picture of the atmosphere, which is useful for
weather precipitation.
V.1. Measurement of different elements:
The energy of solar radiation depend on energy of photons with different
frequencies. The total energy of solar radiation can be considered as the addition of
energies at all emitted frequencies.
E=E1+E2+E3+....En
where: E1= h * ν1
E2 = h * ν2
E3 = h * ν3
En = hνn
Every molecule will, depending on its characteristics; absorb radiation of a
particular frequency. In atmosphere different molecules will absorb different frequencies.
Satellite uses spectrometer to measure the frequency spectrum of light radiation, reradiated by earth surface. If the obtained spectrum is compared with the spectrum of sun
radiation, components in the earths atmosphere can be determined.
This technique can be used to measure water vapor in the atmosphere. Water
molecule in the earths atmosphere will absorb solar radiation emitted by earth surface. As
water vapor will absorb radiation of only certain wavelength, frequency spectrum
obtained by satellite will depend on the atmospheric water vapor concentration. Also just
by changing the frequency of the observation we can measure concentration of different
elements.
31
Precision of measurement using this technique is only 30­40% as water has
complex spectrum as compared with other gases, also most of the water vapor
concentration is near earth surface in 5000m, which is a large distance from satellite
therefore hard to detect. But, this method can be used measure global water vapor
distribution and changes in the concentration.
Figure 31 : Advanced Microwave Scanning Radiometer(AMSR) will observe various physical content
concerning water (H2O) by receiving weak microwaves to be naturally radiated from the Earth's surface
and atmosphere (for example, water vapor content, precipitation, sea surface temperature, sea surface
wind, sea ice, etc.) and also regardless of day or night, the presence of cloud. These sensors aim at
collecting energy. ( Ref: V.1.1 )
V.2. Wind Speed :
Sea wind Scatterometer is used for wind speed and direction over sea surface
measurement with high accuracy. This method can provide accurate measurements over
90% ice free ocean surface. Sea wind Scatterometer uses indirect approach for
measurement of wind speed over ocean surface. Change in wind speed will cause change
in the roughness of ocean surface, which will change the backscattered power.
Figure 32 : The SeaWinds will use a one meter diameter dish antenna with two beams rotated about the
satellite nadir axis at 18 RPM. SeaWinds radiates and receives microwave pulses at a frequency of 13.4
GHz across on 1800 km wide swath. ( Ref: V.2.1 )
32
V.3. Balloons and rockets:
Balloons are used for measuring meteorological data, such as temperature, pressure,
humidity atmospheric composition among other. Weather balloons carry equipment not
only for measuring the atmosphere but also for pinpointing its position and a
communication system for transmitting live-data to a ground station. Balloons are quite
cheap to implement, there are no complicated mechanics or propulsion systems. They are
often filled with helium, which is lighter than air and it is an inert gas ( Ref: V.1). There
are different types of balloons, small balloons called "pilot balloons" are about 1m in
diameter, and there are much larger balloons called "teardrop balloons". Different sizes
means that they are used for different purposes . The smaller ones are visually followed to
obtain data for the computation of wind speed and direction at different levels in the
atmosphere. The larger balloons are able to carry more equipment and are used for higher
altitudes. Balloons can reach a height of 20-40km ( Ref: V.2 ) ( Ref: V.1 ). Airplane travel
up to about half of that height. Well up in the atmosphere the balloon eventually bursts
and fall to the ground. Normally balloons are equipped with a parachute to facilitate, in
some cases, the reuse of the equipment. Balloons are limited in geographic and altitude
coverage since they require a launch site, often a meteorological station. But the modest
costs involved often makes them the choice for various atmospheric observations ( Ref:
V.2 ).
In figure 33, there is group of student assisting a researcher on the release of a
sounding balloon. This is an experimental balloon of a diameter of about 1.5 meters that
reach the height of 8km. A radiosond transmitted data back to the ground and data was
recorded. Temperature and pressure is registered in figure 34.
Figure 33 : A group of people releasing a sounding balloon in Vancouver Canada at about 49° Latitude
and 123° Longitude ( Ref: V.3 )
33
Figure 34 : The temperature observations are shown as dark red dots and blue circles when the sonde
was ascending and descending, respectively. Dew point is in green. For reference, dry adiabats are in
orange, and a moist adiabat is the violet dashed line ( Ref: V.3 )
Rockets evolved rapidly during the second world war. Not only for destructive
purposes but also for atmospheric observations.
Obviously, rockets have more costs but have a great advantage in altitude reach
Rockets travel up to 76km ( Ref: V.1 ). These are therefore used for sounding the
upper atmosphere in a more vertical ascend than balloons that has a ascent depending
heavily on winds.
34
VI.
References:
VI.1. Bibliography:
• Blue => B.J. Skinner, S.C. Porter, D.B. Botkin: The Blue Planet
2:nd edition, John Wiley & Sons. Inc., USA, 1999
• Salby => Murry L. Salby: Fundamentals of Atmospheric Physics
Academic Press, Inc., USA, 1996
VI.2. Internet resources:
II. Atmosphere history:
•
II => http://www.geocities.com/CapeCanaveral/7639/atmosphere/atmosevo.htm
III. Structure and functions of each layer of the atmosphere:
III.1. Layers:
• III.1 => http://csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html
•
III.1.a (Earth's atmosphere) =>
http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Atmosphere.
shtml
•
III.1.b => http://www.oulu.fi/~spaceweb/textbook/ionosphere.html
•
III.1.1.Ionosphere => http://www.haarp.alaska.edu/haarp/ionindex.html
•
III.1.2.Mesosphere =>
http://www.ace.mmu.ac.uk/eae/Atmosphere/Older/Mesosphere.html
•
III.1.3.Stratosphere => http://www.metoffice.com/research/stratosphere/
III.2. Winds:
•
III.2a => http://sync.usatoday.com/weather/photos/press2-470.jpg
http://sync.usatoday.com/weather/photos/press-3-470.jpg
•
III.2b => http://apollo.lsc.vsc.edu/classes/met130/notes/chapter9/pg.html
35
•
III.2.1 => http://zebu.uoregon.edu/~js/glossary/coriolis_effect.html
•
III.2.2 => http://calspace.ucsd.edu/virtualmuseum/climatechange1/08_1.shtml
•
III.2.3 => http://sd.znet.com/~aringler/jet.htm
•
III.2.4 Cell => http://www.physicalgeography.net/fundamentals/7p.html
•
http://sparce.evac.ou.edu/q_and_a/air_circulation.htm ( III.2 )
•
http://www.weatherquestions.com/What_causes_the_jet_stream.htm ( III.2 )
•
http://www.espere.net/Unitedkingdom/water/uk_measurement.html ( III.2 )
•
http://kids.earth.nasa.gov/archive/nino/global.html ( III.2 )
III.3. Temperature:
• III.3.1 => http://www.greeningearthsociety.org/wca/2004/wca_21b.html
•
III.3.2 => http://www.aip.org/history/climate/20ctrend.htm#temp2002
•
III.3.3 => http://www.tpub.com/weather2/3-2.htm
•
III.3.4 => http://www.brighton73.freeserve.co.uk/gw/paleo/paleoclimate.htm
•
III.3.5 => http://www.klimadiagramme.de/
•
http://web.utk.edu/~grissino/ website about tree-rings, with tree-ring dating,
dendrochronology,... ( III.3 )
•
http://www.ngdc.noaa.gov/paleo/ei/ei_reconsa.html : Temperature reconstructions
( III.3 )
•
http://www.atmosphere.mpg.de/enid/gt.html ( III.3 )
•
http://www.atmosphere.mpg.de/enid/5057ce0c8397e666f5a77ee2a0017790,55a30
4092d09/15z.html ( III.3 )
•
http://www.newscientist.com/hottopics/climate/climate.jsp?id=22354400 ( III.3 )
•
http://www.ngdc.noaa.gov/paleo/pubs/mann2003b/mann2003b.html ( III.3 )
36
•
http://www.ngdc.noaa.gov/paleo/globalwarming/paleolast.html ( III.3 )
IV. Interactions with biosphere, geosphere, and hydrosphere:
•
IV.1 => http://www.geog.umd.edu/biogeomodeling/ABINTERACT/
•
IV.2 => http://www.hamburger-bildungsserver.de
•
IV.3 => http://wings.avkids.com
•
IV.4 => http://www.thegreenschool.fsnet.co.uk
•
IV.5 => http://www.solarviews.com
•
IV.6 => http://www.cotf.edu
•
IV.7 => http://www.classzone.com
•
IV.8 => http://www.ucmp.berkeley.edu
• IV.9 => University of Illinois:
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hyd/bdgt.rxml V. Measurement techniques:
•
V.1 => Infoplease Encyclopedia:
http://www.infoplease.com/ce6/sci/A0851701.html
•
V.1.1 => http://hgssac02.eoc.nasda.go.jp/satellite/sendata/amsr_e.html
•
V.2 => http://www.ciesin.org/docs/011-489/011-489.html
•
V.2.1 => http://hgssac02.eoc.nasda.go.jp/satellite/sendata/seawinds_e.html
•
V.3 => A balloon sounding made by ``Earth and Oceans Science at UBC'', The
University of British Columbia, Vancouver Canada:
http://www.eos.ubc.ca/courses/atsc201/A201Resources/SoundingUBC/BalloonLa
unch.html
37