testing the super-greenhouse thermostat with eos observations dan feldman yly sunday meeting...
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![Page 1: Testing the Super-Greenhouse Thermostat with EOS observations Dan Feldman YLY Sunday meeting 10/30/05](https://reader030.vdocument.in/reader030/viewer/2022032704/56649d565503460f94a3494a/html5/thumbnails/1.jpg)
Testing the Super-Greenhouse Thermostat with EOS
observationsDan Feldman
YLY Sunday meeting
10/30/05
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The Super Greenhouse Effect
• First proposed by Collins and Ramanathan, 1991
• Feedback relationship between warm SSTs and production of anvil cirrus leads to thermostat
• Used ERBE data for 1987 El Nino year
– 0.2-50 um band– 0.2-5 um band– 5-50 um band
• Proposed an upper limit to SSTs as governed by this mechanism.
From Collins and Ramanathan, 1991
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Super Greenhouse Knowns• Tropical SSTs are stable• H2O greenhouse effect
increases rapidly for SST>300 K
• Warm SSTs associated with increased convection
• Anvil cirrus efficiently reflect SW radiation, and detrained evaporation humidifies upper troposphere
From Collins and Ramanathan, 1991
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Super Greenhouse Unknowns
• Can tropical dynamics explain SST stability?• Are other mechanisms of poleward heat transport able to
explain SST observations• Is the radiative impact of anvil cirrus a strong and local
function of SSTs >300 K leading to a stable negative feedback?
From Wallace, 1991
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Observations of Cirrus Character
• From ISCCP data
From Fu et al, 1992
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Modeling Efforts
• Hartmann et al propose Fixed Anvil Temperature from:– Clausius-Clapeyron
definition of saturation vapor pressure dependence on temperature.
– Dependence of emissivity of rotational lines of water vapor on vapor pressure.
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EOS observations• MLS sensitive to UT H2O and Cloud IWC• Observations of MLS tend to support Super Greenhouse
Hypothesis.• AQUA can detect the following at 45 km spatial
resolution:– UT H2O (from AIRS standard product)– Cloud cover & cloud top temperature (from AIRS standard
product)– SST (from AIRS standard product)– Night-time cirrus for OD>0.1 (from AIRS, Kahn et al, 2003)– Shortwave Albedo (from CERES)
• With these products, detailed radiative forcing calculations may be able to address the causal or correlative relationship between anvil cirrus and warm SSTs.