Introduction to Meteorology Evolution and Composition of the

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Introduction to MeteorologyEvolution and
Composition of the atmosphere

• Leila M. V. Carvalho

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In the beginning
4.5 billion years ago formation of our solar
system from gas and dust (nebula) generated from
supernova explosion
http//www.aerospaceweb.org/question/astronomy/q02
47.shtml
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THE SOLAR SYSTEM
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PLANETS OF THE SOLAR SYSTEM NOT TO SCALE
TERRESTRIAL PLANETS (OR ROCKY PLANETS)
Earth
Venus
Mars
Mercury
GAS PLANETS (OR JOVIAL PLANETS)
Neptune
Jupiter
Saturn
Uranus
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Earth first atmosphere

• The original atmosphere was primarily helium (He)
  and hydrogen (H).
• Heat from the still-molten crust, the sun, and a
  probably enhanced solar wind, dissipated this
  atmosphere.
• Gravity is important to keep an atmosphere. H, He
  have low molecular weight and may have achieved
  the escape velocity (the velocity necessary to
  escape gravity)
• Other explanations gases would have been removed
  by collision between the growing Earth and other
  large bodies (failed planets). The tremendous
  energy released may have ejected the early
  atmosphere
• This theory explains the origin of the Moon and
  the tilting of the Earth axis to 23o
• (http//www.psrd.hawaii.edu/Dec98/OriginEarthMoon.
  html)

Artist impression of the giant impact that
created the Moon. The sizes of the proto-Earth
and the impactor are comparable with the results
of computer simulations from the 90's. More
recent simulations show the Earth-Moon system
could also have resulted from a relatively
smaller impactor
http//en.wikipedia.org/wiki/Earth27s_atmosphere
Evolution_of_Earth.27s_atmosphere
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The second atmosphere 4.4 billion years ago

• About 4.4 billion years ago, the surface had
  cooled enough to form a crust.
• Many volcanoes released steam, carbon dioxide,
  and ammonia. This led to the early "second
  atmosphere", which was primarily carbon dioxide
  and water vapor, with some nitrogen but virtually
  no oxygen.
• Additional water was imported by collisions,
  probably with asteroids ejected from the
  asteroid belt under the influence of Jupiter's
  gravity.
• As it cooled much of the carbon dioxide was
  dissolved in the seas and precipitated out as
  carbonates.
• Simulations run at the University of Waterloo and
  University of Colorado suggest that it may have
  had up to 40 hydrogen.
• It is generally believed that the greenhouse
  effect, caused by high levels of carbon dioxide
  and methane, kept the Earth from freezing.

Early Earth - The First Billion Years Lava
flowing from Earth's partially molten interior
spread over the Earth's surface and solidified to
form a thin crust, the rain evaporating on
contact with the hot ground. As the temperature
dropped, the oceans formed.
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Life and the formation of the third atmosphere

• cyanobacteriaS existed approximately 3.3 billion
  years ago and were the first oxygen-producing
  evolving phototropic organisms.
• They were responsible for the initial conversion
  of the Earth's atmosphere from an anoxic state to
  an oxic state (that is, from a state without
  oxygen to a state with oxygen) during the period
  2.7 to 2.2 billion years ago.
• They were the first to carry out oxygenic
  photosynthesis, and were able to produce oxygen
  while sequestering carbon dioxide in organic
  molecules, playing a major role in oxygenating
  the atmosphere. This is often referred to as the
  Oxygen Catastrophe. (oxygen was toxic to the
  microscopic anaerobic organisms dominant then.)
• The increase in the concentration of oxygen in
  the atmosphere required time because iron and
  other elements in the Earth's crust reacted with
  oxygen, removing it from the atmosphere.

Cyanobacterias
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The third atmosphere

• Photosynthesizing plants later evolved and
  continued releasing oxygen and sequestering
  carbon dioxide.
• As oxygen was released, it reacted with ammonia
  to release nitrogen.
• Bacteria also converted ammonia (NH3) into
  nitrogen, but most of the nitrogen currently in
  the atmosphere resulted from sunlight-powered
  photolysis of ammonia
• As more plants appeared, the levels of oxygen
  increased significantly, while carbon dioxide
  levels dropped.
• At first the oxygen combined with various
  elements, but eventually oxygen accumulated in
  the atmosphere, contributing to Cambrian
  explosion and further evolution.

Cambrian Period 543-490 Million Yrs
Siberia
Laurentia
Gondwana
Baltica
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Oxygen increases The ozone layer is formed, life
can migrate to the continents

• With the appearance of an ozone layer life-forms
  were better protected from ultraviolet radiation.
  - life over continents (450 mi years ago)
• Between 200 and 250 million years ago, up to 35
  of the atmosphere was oxygen (as found in bubbles
  of ancient atmosphere preserved in amber).
• This modern atmosphere has a composition which is
  enforced by oceanic blue-green algae as well as
  geological processes.

Ancient Amphibians http//news.nationalgeographic
.com/news/bigphotos/10940810.html
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http//www.chem.arizona.edu/prise/w8/historylife2.
pdf

• O2 does not remain naturally free in an
  atmosphere but tends to be consumed by inorganic
  chemical reactions, and by animals, bacteria, and
  even land plants at night. CO2 tends to be
  produced by respiration and decomposition and
  oxidation of organic matter.

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• O2 would vanish within a few million years by
  chemical reactions, and CO2 dissolves in water
  and would be gone in millennia if not replaced.
  Both are maintained by biological productivity
  and geological forces seemingly working
  hand-in-hand to maintain reasonably steady levels
  over millions of years.

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PRESENT ATMOSPHERE BEFORE THE INDUSTRIAL
REVOLUTION
O221
N2 78
per volume
Water vapor H2O 0-4 (Variable) Carbon
dioxide CO2 0.03 (Variable)
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Steady state and residence time definitions
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Steady state and residence time
Consider a gas that is constantly being cycled
between the atmosphere and the Earths surface
physical processes (volcanic eruptions,
biological processes, etc) or by chemical
processes (reaction between gases). If we
consider the atmosphere as a reservoir for this
gas, the concentration of the gas will remain
constant so long as the input rate output rate
concentration of the gas is in a steady state.
Individual molecules stay in the atmosphere for
only a finite period of time before they are
removed by whatever output processes are active.
The average length of time that individual
molecules of a given substance remain in the
atmosphere is called the residence time
These two figures are schematically showing gases
with high and low residence time. If arrows are
indicating the rate that a substance enters and
exits the atmosphere in a steady state, which
figure represents the long residence time?
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Permanent and variable gases in the atmosphere
Constitute approximately 99.999 of the
atmosphere and occur in nearly constant
proportion throughout the atmospheres lowest
80km HOMOSPHERE What does it mean?
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How to compute the residence time?

• Divide the mass of the substance in the
  atmosphere (in kilograms) by the rate at which
  the substance enters and exits the atmosphere (in
  kilograms per year).

Consider a box or reservoir
Fout
m X
L
D
i.e.
t Residence time (yr) m mass (kg) FoutFlux
outside the volume (or reservoir) L chemical
loss (kg/yr) of m converting into X D
Deposition (kg/yr)

• Thus everything else being equal, gases that are
  rapidly exchanged between Earths surface and the
  atmosphere have brief residence times, as do
  gases that have relatively low atmospheric
  concentrations.

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Example

• The mass of nitrogen in the atmosphere is 4 x
  1018 kg, and its sinks from the atmosphere
  include (i) biological nitrogen fixation by
  bacteria, 2 x 1011 kg yr-1 (ii) production of NO
  in thunderstorms, 7 x 1010 yr-1 (iii) chemical
  synthesis of ammonia, 5 x 1010 kg yr-1 (all data
  refer to loss of nitrogen). Calculate the
  residence time of nitrogen in the atmosphere.

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Water Vapor
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Water vapor from satellite
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Water vapor

• Water vapor is not the same as droplets it is a
  gas
• Main source evaporation
• Concentration decreases rapidly with altitude
• Most atmospheric water vapor lowest 5km (3mi) of
  the atmosphere in quantities the vary from 1-4
• Outside tropics it does not exceed 2
• It is constantly cycled between the planet and
  the atmosphere in the so called hydrological
  cycle.
• Water evaporates from river, oceans lakes, ice
  sheets, and underground water (removed from the
  soil sometimes by vegetation)

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Question to discuss with your partner

• What in your opinion is the most important role
  of tropical rainforests such as the Amazon forest
  (justify your answer)
• A) contribution for the Earth input of O2
• B) contribution for input H2O vapor
• C) (A) and (B) are correct
• D) Neither (A) or (B) is correct

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Carbon dioxide

• CO2 currently accounts for about 0.038 of the
  atmospheres volume.
• When a gas occupies such a small proportion of
  the atmosphere, we often express its content as
  part per million (ppm) - today 380 ppm.
• Sources plant, animal respiration, decay of
  organic material, volcanic eruptions, natural
  anthropogenic (human produced) combustion.
• CO2 is removed by photosynthesis by plants
• CO2 gas a residence time of about 150 yrs.

How do you explain the cycles observed for CO2?
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6.3
-2.3
-2.3
1.6
3.3 GtC
Metric ton 1,000 kilograms (2,205 pounds) Unity
of flux metric ton/year Gigatons 109 ton 1012
kg
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Methane CH4

• about 3.5 billion years agothere was 1,000 times
  as much methane in the atmosphere as there is
  now. The earliest methane was released into the
  atmosphere by volcanic activity.
• With life and increase in O2 methane decreased
  (reaction with OH).
• With industrialization the rate of increase
  accelerated so that values have more than doubled
  over the last 200yrs ( 1.7 ppm in 1999)
• The residence time for methane is about 10 yrs.
• The current input of CH4 is approximately equal
  to its natural removal
• CH4 is a very efficient greenhouse gas

Less industrial production and decrease of wet
lands (drought)
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Hum it seems something else happened these past
years that might change the trends observed
before and potentially cause a climate shift (if
persisted).
From the following article A sleeping
giant? Nature Reports Climate Change (2009)
Published online 5 March 2009 doi10.1038/climate
.2009.24
Could this increase be because methane has been
released in the atmosphere because global warming
has released the methane that was trapped under
the permafrost? If that is true, the increase of
methane, an efficient greenhouse gas, might
increase global warming and cause important
climate shifts
The average atmospheric concentration of methane
shot up suddenly in 2007, having remained stable
for a decade. Data shown are from the Advanced
Global Atmospheric Gases Experiment and the
Australian Commonwealth Scientific and Industrial
Research Organisation, courtesy of Matt Rigby
http//www.nature.com/climate/2009/0904/full/clima
te.2009.24.html
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What is greenhouse effect?
CO2, CH4, H20
IR - heat
UV, VIS
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Ozone O3

• Ozone is observed in the stratosphere (above
  20km) and in the troposphere (below 12 km)
• In the stratosphere 25km at concentration of
  15ppm (that is 15 out of every one million
  molecules is ozone), is essential for life on
  Earth!
• In the lower atmosphere occur in highly polluted
  urban areas and association with forest burning.
  Can cause irritation to lungs, eyes, and damage
  to vegetation.
• Concentration in polluted urban areas up to 0.15
  ppm (that is, 15 out of every 100 million
  molecules are ozone)

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(No Transcript)
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But how is ozone formed in the stratosphere
?http//www.ccpo.odu.edu/SEES/ozone/oz_class.htm

NASA
2. Ozone and oxygen atoms are continuously being
interconverted as solar UV breaks ozone and the
oxygen atmom reacts with another oxygen molecule
(FAST)
1. Oxygen molecules are photolyzed, yielding 2
oxygen atoms (SLOW)
O2
This interconversion process converts UV
radiation into Thermal energy, heating the
stratosphere
3. Ozone is lost by the reaction of the oxygen
atom or the ozone molecule with each other, or
some other trace gas such as chorine (SLOW)
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Typical reaction in the Stratosphere
UV solar radiation ? 240nm (wave length ) h
Plank Constant c speed of light
1) Production of free oxygen
O2 hc/? --gt O O
O3 hc/? --gt O2 O O O2 M --gt O3 M The
M is another molecule (typically N2 or O2, the
two most abundant molecules in the atmosphere).
It carries away the extra energy of this
reaction. This process of absorption is an
extremely efficient, ultraviolet radiation is
effectively screened out before it reaches
Earth's surface.
What happens if Chlorine , Bromine or Fluor (more
reactive) take part in this reaction?
O2 hc/? --gt O O ClO O --gt O2 Cl Cl
O3 --gt O2 ClO
Ex ClO (chlorine monoxide)
Net O3 O3 --gt 3 O2
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Discussion
WHY THE O3 PEAK IS OBSERVED AROUND 30Km AND NOT
ABOVE, WHERE SOLAR RADIATION IS HIGHER, OR
BELOW, WHERE THE DENSITY OF O2 IS HIGHER?
Did you know that Dobson Unit (DU) is a measure
of the "thickness" of the ozone layer? Imagine
that all of the overhead ozone molecules (spread
over the depth of the stratosphere) could be
brought down to the surface (at standard
temperature and pressure). This "layer" of ozone
would only be about 3 millimeters (mm) thick,
equivalent to the height of two stacked pennies.
This amount of ozone has a Dobson Unit value of
300 DU (approximately the global average of total
ozone).
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But what is the ozone hole? Why does it occur?
Is it caused by natural or is it anthropogenic
induced ?
O2
LOW
HIGH OZONE
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During the winter of the SH polar regions do not
receive solar radiation and therefore by the
beginning of the spring there is a minimum in the
stratospheric ozone. (therefore, the minimum
ozone is a natural feature)
However, remember that if chlorine, bromine or
flour are present, then when free oxygen that
begins to form during spring, combines with these
components. The result is less total ozone and
the increase in the ozone hole over polar
stratosphere
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Aerosols

• Definition small solid particles and liquid
  droplets in the air (excluding cloud droplets and
  precipitation).
• Can be formed by human or natural processes.
• Normal concentration 10,000 particles per cubic
  centimeter over land surface ( 17,000 particles
  per cubic inch)
• Size below 0.1 µm (Aitken nuclei)
• 0.1 1.0 µm (large particle)
• gt 1 µm giant particle

Fine aerosols
Coarse aerosols
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Effects in the atmosphere and society
Dust Storm Texas 1935
Smog in NY city
Caused by burning of fossil fuels, coal and
industrial activity Reduce visibility, solar
radiation at the surface, Serious impacts on
health
Reduce visibility, solar radiation at the
surface, Serious impacts on health
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Did you know?
On average, each breath a person takes brings
into the lungs about 1000cm3 (1 liter, or 64in.3)
of air. Given the average size and concentration
of aerosols, each of us draws about 1 trillion
aerosols into our lungs several times each
minute, or about two table spoons of solid each
day!
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Discussions and conclusions

• Earth had three atmospheres the composition of
  the third one is completely linked to the
  existence of life in our planet 21 O2 and 78 N2
  
• The ozone layer formed only recently ( 7 mi yrs)
• Green house gases have been important to maintain
  the temperature of earth above freezing.
• Human activity has increased the amount of
  greenhouse gases in the atmosphere
• The ozone hole is a natural feature of the
  atmosphere. Its increase over time is due to
  human activity (input of chlorine and bromine
  that reacts with free oxigen)
• Aerosols are important component of the
  atmosphere (they may be of natural sources or
  human produced)

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Training a few concepts
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How was the 2010 SH ozone hole compared with
previous years?
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http//www.esrl.noaa.gov/gmd/dv/spo_oz/spototal.ht
ml
Record low October 1993 Pinatubo released more
Chlorine in the atmosphere
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Important concepts

• Ultraviolet radiation is divided into three
  components UV-A (315 to 400 nm), UV-B (280 to
  315 nm) and UV-C (less than 280 nm). The shorter
  wavelengths that comprise UV-B are the most
  dangerous portion of UV radiation that can reach
  ground level
• Atmospheric ozone shields life at the surface
  from most of the UV-B and almost all of the UV-C
• All forms of UV radiation are reduced by cloud
  cover. Persistent lack of cloud cover in some
  regions (e.g. Australia and South Africa)
  increases the danger from UV radiation compared
  to similar latitudes in the Northern Hemisphere

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Why do we observe values so close to zero here???
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January 3, 2011 total ozone estimated by UV