a new convection scheme for studying the runaway greenhouse atmosphere
Abstract
The runaway greenhouse atmosphere has been extensively studied with 1D radiative-convective models. However, the dynamical structure, and the spatial distribution of water vapor and clouds are still poorly understood. Conventional general circulation models cannot simulate the runaway greenhouse atmosphere, not only because they assume water vapor is dilute in the atmosphere and use the dilute form of moist enthalpy to conserve energy but also because they ignore the energy carried away by precipitation (the sum of internal energy and potential energy of the condensate). Here we develop a 1D column model with a new convection scheme using the primitive physical equations to describe the energy change without any approximations, which means this scheme is always valid no matter what the condensable substance is, and whether the condensable substance is dilute in the atmosphere. Therefore an idealized general circulation model coupled with such a scheme could be employed to explore the climate dynamics of the runaway greenhouse atmosphere. First, the present Earth's atmosphere is studied in the 1D column model. Simulation results show that even if the water vapor concentration is as small as the present Earth's, the energy flux associated with precipitation is large, ~40 W m-2. Although most of it is balanced by the energy flux associated with evaporation, the residual part is still not negligible, ~2 W m-2. Next, a hot water-rich atmosphere on a planet with a high eccentricity orbit is studied in the 1D column model. We show that near the apastron, the surface temperature only drops by a small amount although the planet undergoes long and cold winter, due to the large thermal inertia of the atmosphere. In both cases, it is verified that the convection scheme conserves energy, and hence is suitable for future work involving general circulation models. Evolution of the net radiative flux at the top of the model (upper panel) and the net evaporation flux at the surface (lower panel) for the present Earth's condition.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.P21B1726D
- Keywords:
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- 0343 ATMOSPHERIC COMPOSITION AND STRUCTURE Planetary atmospheres