Abstract
Understanding surface temperature is important for habitability. Recent
work on Mars has found that the dependence of surface temperature on
elevation (surface lapse rate) converges to zero in the limit of a thin
$\mathrm{CO_2}$ atmosphere. However, the mechanisms
that control the surface lapse rate are still not fully understood. It
remains unclear how the surface lapse rate depends on both greenhouse
effect and surface pressure. Here, we use climate models to study when
and why “mountaintops are cold”. We find the tropical surface lapse
rate increases with the greenhouse effect and with surface pressure. The
greenhouse effect dominates the surface lapse rate transition and is
robust across latitudes. The pressure effect is important at low
latitudes in moderately opaque ($\tau
\sim 0.1$) atmospheres. A simple model provides insights
into the mechanisms of the transition. Our results suggest that
topographic cold-trapping may be important for the climate of arid
planets.