General Structure and Properties of the Earth

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General Structure and Properties of the Earths
Atmosphere

• global circulation
• atmospheric radiation
• weather patterns
• atmospheric composition

Dr Tony Cox ERCA 2004 -Lecture 1
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Temperature structure of the Atmosphere
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Horse latitudes Descending Limb ?
Hadley Cell
? Rising Limb doldrums
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Jetstreams at (12km)
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Max.Outgoing earth radiation Max. Solar
radiation
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Absorbtion and re-emission up- and
downwards ?Warming at the surface
Black body emission at 280 K
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Coriolis Force - This is a force which is caused
by the rotation of the earth and acts
perpendicular to the direction of motion. It
results from the change in radius of rotation
with latitude and the need to conserve angular
momentum, by developing zonal motion, I.e. in the
direction of the earths rotation. The
hypothetical force producing this motion
perpendicular to the initial direction of
transport is called the Coriolis force. The
horizontal component of the Coriolis force is
directed perpendicular to the horizontal velocity
vector to the right in the N.Hemisphere and to
the left in the S.Hemisphere. The Coriolis force
has the magnitude Fc 2?Vhsin? (?
angular velocity Vh horizontal velocity ?
latitude) The force is thus a minimum at the
equator and maximum at the poles. The Coriolis
and the horizontal pressure force tend to balance
each other, see examples above for cyclonic and
anticyclonic pressure systems
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10 km
Cirrus
Cumulus
Stratus
0 km
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Orographic Clouds
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Cross-section of a Tropical Cyclone
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Issues in Atmospheric Chemistry
Tropics
High Latitudes
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Reservoir Atmospheric Non-atmospheric Carbon
cycle CO2 CaCO3 (carbonate) CO, CH4,
VOC biomass Oxygen cycle O2 sulphate CO2 CaC
O3 Nitrogen cycle NOx nitrate N2O,
N2,NH3 fixed organic N Sulphur cycle H2S,
OCS sulphate, sulphides SO2, H2SO4 sulphur in
biomass
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diameter
Fall speed
1
10 ms-1
lt10-3 ms-1
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Sources of the Minor Constituents
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Sources of the Minor Constituents

• The majority of the minor constituents of the
  troposphere originate from emissions from the
  Earth's surface.
• Natural emissions are primarily biogenic although
  volcanism accounts for significant amounts of
  atmospheric sulphur. Man made emissions result
  from energy production, industrial activity and
  agricultural practices.
• It frequently occurs that the chemical
  transformation of one minor constituent in the
  atmosphere creates one or more products which may
  themselves have significant roles in the overall
  chemical system. Knowledge of atmospheric
  degradation pathways is therefore important for
  understanding the behaviour of many minor
  constituents, gases and aerosols.
• Several important trace species enter the
  troposphere from the stratosphere. Most notable
  is O3 which plays a central role in tropospheric
  chemistry. Other species include HNO3 and HCl
  which result from stratospheric NOx and ClOx
  chemistry.

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Sinks of the Minor Constituents
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Deposition to the underlying surface
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Chemical Removal
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Lifetimes and Atmospheric Concentrations

• The atmospheric concentration of a particular gas
  emitted to the atmosphere is determined by its
  emission rate, and its atmospheric lifetime.
• For well mixed gases (those with lifetimes of
  several months or greater), the time evolution of
  concentration can be represented by a simple box
  model.
• A is the concentration of the gas of interest,
  emitted into the atmosphere at rate R.

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Lifetimes and Atmospheric Concentrations
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Emissions regulated under Montreal Protocol
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?1/2 5 yr i.e. kII 0.20 yr-1
kr 6.8x10-15 s-1 OH CH3CCl3 ?
products kII krOHmean OH 9.2x105
molecule cm-3 ?
Measurements of surface concentrations of
atmospheric CH3CCl3