Stratospheric Aerosol and Gas Experiment

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Stratospheric Aerosol and Gas Experiment (SAGE)
III Science Overview
Allan David Risley, Jr. Atmospheric Scientist SAIC
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What Are External Forcings of Climate? Processes
that have cause and effect
Influences outside the Earths environment solar
energy variability (e.g. 11 year cycle)
Influences within the Earths environment volcanic
eruptions greenhouse gas CFC emissions human
land-use activities
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Understanding External Forces requires
characterization of their variability

Seasonal and interannual variablity
Carbon dioxide increases of the past 40 years
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Understanding External Forces requires
characterization of their variability

Geographical variability
Aerosol forcing is regional in nature
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What are Climate Feedback Loops? - interactions
between climate processes that can amplify or
suppress external forces

Water Cycle Feedback
Climate warms
Greenhouse effect increases
More water evaporates
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Coupled Interactions across Climatic Processes

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Ozone loss in the presence of increasing CFC
concentrations
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Monitor the abundance of ozone and
ozone-destructive species
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Understand the distribution of aerosols and their
radiative impact
Eruption of Mt PinatuboJune 1991
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ERBE SAGE Observations of the Mt. Pinatubo
Eruption
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SAGE III Mission Objectives
Characterize the variability of aerosols, O3,
H2O, NO2, NO3, OClO, temperature and pressure.
Investigate the role of the measured species in
the radiation budget, atmospheric chemistry and
in biogeochemical and hydrologic cycles.
Extend the SAM II, SAGE I, and SAGE II data sets,
enabling the detection of long-term trends.
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How does SAGE III work?

• SAGE III instrument measures the reduction of
  solar radiation (light)
• Similar to a solar photometer (light energy is
  detected and converted into a current which is
  measured)
• Fundamental physics based on Beers Law
• I Io exp(-? ds)
• where I, Io solar radiation intensity
• ? extinction
• ds air mass path length

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Beers Law
Absorption or scattering of energy
Path length
Received energy
Transmitted energy
I Io exp(-? ds)
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Measurements from space allow profiles to be
derived along the line-of-sight tangent point
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SAGE III Meteor 3M/Mission

• Part of NASAs Earth Observation System (EOS)
• Cooperative effort between NASA and the Russian
  Space Agency
• SAGE III managed by NASA LaRC
• Launched December 2001
• 3-year lifetime

Zenit 2 launch from Baikonur Cosodrome
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