Cold Air Rises: Profound Effects of Vapor Buoyancy on Earth's Climate - Livestream

 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. As a result, cold air rises in the tropical free troposphere. We further show that vapor buoyancy increases subtropical stratiform low clouds, enhances thermal radiation, and favors convective aggregation. However, some state-of-the-art climate models fail to properly represent vapor buoyancy. This flaw leads to inaccurate simulations of cloud distributions - the largest uncertainty in predicting climate change.

Speaker: Da Yang, UC Davis

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