Observations of the climate system GPC Ch1

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Observations of the climate system (GPC Ch1)

• 1.1 definition of climate synthesis of weather
  in a particular region
• Usually averages and measures of variability over
  space and time
• e.g. monthly mean and standard deviation of
  surface temperature over Greenland

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1.2 Atmospheric temperature

• Lapse rate rate of change of temperature with
  height
• ?-dT/dz
• 6.5 K/km in troposphere
• Q what determines the structure of the
  troposphere? Why is it important?

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Lapse rate varies in latitude and season
Def temperature inversion region of negative
lapse rate
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PO Fig 7.5 - zonal mean cross section of temp
Def zonal average average of a quantity over
all longitudes
ANN
DJF
JJA
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Zonal averaged surface air temperature
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1.3 Atmospheric composition
Mass of atm 5.14x1018kg Mass of
ocn 1.39x1021kg
Important for radiation Water vapor CO2 Ozone Met
hane N2O
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Mauna Loa CO2 concentration
Global average methane concentration ppmvparts
per million by volume
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1.5 Atmospheric humidity
Moisture in the air is generally confined to the
lowest few kilometers of the atmosphere Def
specific humidity ratio of the mass of vapor in
a certain volume to the total mass of air and
vapor in the same volume
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PO Fig 12.4 - zonal averaged specific humidity
Distribution depends strongly on temperature
ANN
DJF
JJA
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1.6 The world ocean
71 of earth surface is ocean Average depth
3700m Importance to climate - stores, moves,
releases heat
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Ocean surface temperature
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Vertical temperature and salinity structure of
the ocean at various latitudes. Ocean water
density depends on both temperature and salinity
T
S
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PO Fig 8.4 - zonal mean cross section of ocean
temperature
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1.7 Cryosphere
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Antarctic ice sheet
Ice sheet dynamics
(from http//igloo.gsfc.nasa.gov/wais/eos.html)
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Importance to climate Reflection of
sunlight Insulates ocean from atmosphere
Seasonal cycle of NH sea ice
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Seasonal cycle of SH sea ice
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Snow cover (grey)
Sea ice (blue)
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Areas covered by ice sheet, sea ice, snow about
comparable
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1.8 Land surface
More land in NH than SH - hemispheric asymmetry
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Atmospheric Circulation
Land-sea contrast land warmer than sea low
pressure over land Topography blocks atm flow
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NDVI-seasonal
Satellite Greenness index Normalized Difference
Vegetation Index
August 2000
NDVI RNIR RVIS RNIR Rvis
February 2001
Quantities relevant to climate reflective
properties moisture at the surface
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Rate of change Suppose T(z) is temperature with
height define change ?T T(z2) - T(z1) And
rate of change (with height) ?T/?z (T(z2) -
T(z1)) / (z2-z1) ?T/?z is usually denoted dT/dz
Concept of Balance Suppose X is a property that
changes with time because of various tendencies
on it. Then balance occurs when the tendencies
cancel, i.e. ?X/?t 0