a. Utilized System and Assumptions
The system utilized is basically the same as that of the 1D model
developed by Nakajima et al. (1992), except for the
inclusion of atmospheric motion. In our study, the following
assumptions are made:
- Atmospheric component:
The atmosphere consists of dry air and water vapor. Both
behave as ideal gases with constant specific heat. The
molecular weight of water vapor is the same as dry air.
- Radiative Properties:
There is no absorption of incident solar radiation flux
(shortwave radiation) by the atmosphere. Only water vapor is
assumed to absorb and emit longwave radiation. The absorption
coefficient is constant and independent of
wavelength. Together, these conditions make up a so-called
gray atmosphere.
- Cloud Effect:
The cloud effect is ignored and condensation of water vapor
has no effect on radiation. Additionally, the evaporation of
rain droplets and the processes of cloud physics are not
considered.
- Surface Condition:
The surface is assumed to be always in a heat balanced
ocean. The specific heat of the surface is set to 0 (swamp
condition). Oceanic motion, heat transport, and material
transport are completely ignored. The surface albedo is
constant and set to 0.
- Planetary Condition:
The radius of the planet and the rotation rate are constant.
As can be seen from the above, the system setup used in the present
study is extremely simple. The reason for this is that we are
attempting a 3D version of the study by Nakajima et al. (1992). By
applying the results of Komabayashi (1967) and Ingersoll (1969) to a
reproducible stratosphere/troposphere model, Nakajima et al. (1992)
succeeded in constructing a theoretical framework for a runaway
greenhouse state. The goal of the present study is to move on to the
further step by the use of their framework.
