Exploiting the weak temperature gradient approximation for climate theory on slowly rotating, tidally locked planets
Abstract
Tidally locked planets are subject to extreme temperature variations due to the stellar flux directly warming only one side of the planet. This is important because planets in the habitable zone around M dwarf stars are likely to be tidally locked. Such planets are unlikely to be habitable if their antistellar temperatures are low enough that CO2 will condense. This problem has previously been investigated using GCMs, which explicitly solve for atmospheric dynamics. In order to gain a greater understanding of the effect of different mechanisms on the temperature profile, we use a lower-order energy balance model here. We consider tidally locked planets that rotate slowly enough that we can neglect the Coriolis force, which allows us to assume that atmospheric temperature at any given height is independent of horizontal position (weak temperature gradient approximation). This allows us to easily isolate and contrast the effects of different physical mechanisms, such as greenhouse gas level and surface turbulent exchange, on the resulting temperature profile. We find that the effect of turbulent exchange on climate saturates at fairly low values (very smooth planets), whereas CO2 has a consistently strong effect on climate.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.P21C1674M
- Keywords:
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- 0343 ATMOSPHERIC COMPOSITION AND STRUCTURE / Planetary atmospheres;
- 5405 PLANETARY SCIENCES: SOLID SURFACE PLANETS / Atmospheres;
- 6296 PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS / Extra-solar planets