Formation of Near-surface Atmospheric Inversion and Surface Inversion in Hothouse Climates

Abstract A hothouse climate may develop throughout Earth’s history and its warming future, and on potentially habitable exoplanets near the inner edge of the habitable zone. Previous studies have suggested that near-surface atmospheric inversion (NAIV), with the planetary boundary air temperature being higher than the air temperature adjacent to the surface, is a pronounced phenomenon in hothouse climates. However, the underlying mechanisms are unclear. Here, we show that lower-tropospheric radiative heating is necessary but not independently sufficient in forming the NAIV. Instead, the dynamic heating induced by large-scale subsidence is essential. With the prescribed reasonable large-scale subsidence, NAIV appears in small-domain cloud-resolving simulations, which was not observed in previous studies. Surface evaporative cooling also contributes to the formation of the NAIV. Besides NAIV, we find that surface inversion (SIV), with the air adjacent to the surface being warmer than the underlying sea surface, is also a distinct phenomenon in hothouse climates. SIV is caused by strong surface evaporative cooling and large atmospheric shortwave absorption. These two types of inversion strongly stabilize the atmosphere, weaken atmospheric circulation, dry the free troposphere, and suppress the hydrological cycle.