Science Daily October 24, 2022
The molar mass of water vapour 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 vapour buoyancy and has been considered negligibly small in large-scale climate dynamics. Using theory, reanalysis data and a hierarchy of climate models a team of researchers in the US (UC Davis, Lawrence Livermore National Laboratory, Pacific Northwest National Laboratory) showed that vapour buoyancy has a similar magnitude to thermal buoyancy in the tropical free troposphere. They also showed that vapour 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 vapour buoyancy in the governing equations. According to the researchers this flaw leads to inaccurate simulations of cloud distributions—the largest uncertainty in predicting climate change…read more. TECHNICAL ARTICLEÂ
Low clouds and VB in comprehensive simulations. Credit: Nature Geoscience volume 15, pages781–788 (2022)Â