November 1, 2022
Journal Article

Substantial Influence of Vapour Buoyancy on Tropospheric Air Temperature and Subtropical Cloud

Abstract

The molar mass of water vapor is less than that of dry air, making humid air lighter than dry air at the same temperature and pressure. This effect is known as vapor buoyancy and has been considered negligibly small in large-scale climate dynamics. Here we use theory, reanalysis data, and a hierarchy of climate models to show that vapor buoyancy has a similar magnitude to thermal buoyancy in the tropical free troposphere. We further show that vapor buoyancy makes cold air rise and increases subtropical stratiform low clouds by up to 70% of its climatological value. However, some widely used climate models fail to represent vapor buoyancy in the governing equations. This flaw leads to inaccurate simulations of cloud distributions—the largest uncertainty in predicting climate change.

Published: November 1, 2022

Citation

Yang D., W. Zhou, and S.D. Seidel. 2022. Substantial Influence of Vapour Buoyancy on Tropospheric Air Temperature and Subtropical Cloud. Nature Geoscience 15, no. 10:781–788. PNNL-SA-176724. doi:10.1038/s41561-022-01033-x

Research topics