1. Testing the Super-Greenhouse Thermostat with EOS observations Dan Feldman YLY Sunday meeting 10/30/05

2. 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

3. 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

4. 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

5. Observations of Cirrus Character From ISCCP data From Fu et al, 1992

6. 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.

7. 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.