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The dependency of the structure of the three-dimensional gray atmosphere on the solar constant and the runaway greenhouse states.

Masaki Ishiwatari (Graduate School of Environmental Earth Science, Hokkaido University)
Kensuke Nakajima (Faculty of Science, Kyushu University)
Shin-ichi Takehiro (Faculty of Science, Kyushu University)
Yoshi-Yuki Hayashi (Graduate School of Mathematical Science, University of Tokyo)

Abstract :

We determined the value of the solar constant at which the runaway greenhouse state realizes in the three-dimensional gray atmosphere, and performed the numerical integration of the runaway greenhouse state using the simplified general circulation model (GCM). The radiative active gas is assumed to be only water vapor. The vapor is transparent to solar radiation and has a gray infrared absorption coefficient. This model is equivalent to the system of Nakajima et al. (1992) which defined the runaway greenhouse state, except for the effect of atmospheric dynamics taken into account.

Under various values of the solar constant, integrations of about 1000 day were performed. The atmospheric thermal structure reaches the statistical equilibrium state in about 500 days when the value of solar constant is smaller than 1600 W/m2. However, the atmosphere does not reach the equilibrium state, and instead thermally "runaways" when the solar constant value is larger than 1600 W/m2. Outgoing longwave radiation (OLR) cannot balance out the incident energy flux. The vapor content and the amount of the atmosphere continue to increase as well as the atmospheric temperature and ground temperature.

The pole-equator contrast of distributions of vapor and temperature decreases with increasing solar constant value. As a result of homogenization of the radiation structure, the solar constant value when the "thermally runaway" state realizes corresponds to the upper limit of the outgoing radiation of the model of Nakajima et al. (1992) with the constant value of relative humidity of 60 %. This value of relative humidity is the mean value in the troposphere of three-dimensional calculation. The "thermally runaway" states realized when the value of the solar constant is larger than 1600 W/m2 correspond to the state in which one-dimensional model has no equilibrium solution, that is, the runaway greenhouse state.

Contents
  1. Background and Purpose of Research
    1. Background of Research
    2. Previous Studies on the Runaway Greenhouse State
    3. Problems Investigated in the Present Paper
  2. Model and Experimental Design
    1. Utilized System and Assumptions
    2. Model
    3. Experimental Design and List of Experiments
  3. Results
    1. Are the "runaway state" also be realized in 3D-system ?
    2. The Value of the 3D Runaway Limit
    3. Changes in the Equilibrium State (Circulation Pattern)
    4. Changes in the Equilibrium State (Meridional Structure)
    5. Changes in the Equilibrium State (Precipitation Distribution)
    6. The Runaway Greenhouse State
    7. What Determines a Runaway Limit? (Comparison with the Stratospheric Model)
    8. What Determines a Runaway Limit? (Examination on the Vertical Structure)
    9. What Determines a Runaway Limit? (Description with an Equilibrium Solution of 1D Radiative-Convective Model)
  4. Summary
    1. Conclusion
    2. Implications of the Present Study
    3. Future Themes and Problems

Acknowledgements, References, and Index

  1. Acknowledgements
  2. References
  3. Index
  4. Contact addresses of authors
 Appendices
  1. Chronology of Studies on the Runaway Greenhouse State
  2. A Summary of the results obtained by 1D Radiative-Convective Equilibrium Model
    1. Characteristics of Radiative Equilibrium Solutions: Results of Stratospheric Model
    2. Characteristics of 1D Radiative-Convective Equilibrium Solutions
    3. Dependence of the Upper Limit of Radiation on Relative Humidity
  3. Details of the Model
    1. Basic Equations
    2. Radiation Scheme
    3. Examination on the Vertical Resolution
    4. Changes in Surface Pressure due to Evaporation and Condensation
    5. Moist Convective Adjustment Scheme
    6. Upper Damping Layer
    7. Vertical Filter
  4. Results from Calculations with a Single Damping Layer
    1. Equilibrium State: Meridional Structure of the Troposphere
    2. Equilibrium State: Meridional Structure of the Upper Layer
    3. Equilibrium State: Meridional Distribution of Energy Fluxes
    4. Equilibrium State: Meridional Energy Transport
    5. Runaway Greenhouse State
  5. Atmospheric Structure in Equilibrium States
    1. Global Mean Values
    2. Temperature Distribution and Mass Stream Function (Troposphere)
    3. Condensation Heating Distribution (Troposphere)
    4. Specific Humidity Distribution (Troposphere)
    5. Relative Humidity Distribution (Troposphere)
    6. Zonal Wind Distribution (Troposphere)
    7. Temperature Distribution and Mass Stream Function (Upper Layer)
    8. Zonal Wind Distribution (Upper Layer)
    9. Meridional Distribution of Energy Fluxes
    10. Meridional Energy Transport
    11. Characteristics of Atmospheric Disturbances
  6. Atmospheric Structure in the Runaway Greenhouse State
    1. Time Evolution of Global Mean Values
    2. Time Evolution of Physical Variables
    3. Meridional Structure
    4. Meridional Thermal Structure
    5. Meridional Energy Transport
    6. Characteristics of Atmospheric Disturbances
  7. Images from Performed Experiments
    1. Results from Experiment S1200
    2. Results from Experiment S1380
    3. Results from Experiment S1500
    4. Results from Experiment S1550
    5. Results from Experiment S1570
    6. Results from Experiment S1600
    7. Results from Experiment S1700
    8. Results from Experiment S1800
Received 26 January, 1998; in revised form 21 April, 1998 Nagare Multimedia 98