Published: March 22, 2023

Nadir Jeevanjee, Geophysical Fluid Dynamics Laboratory, National Oceanic and Atmospheric Administration (NOAA)

The surprising fluid dynamics of atmospheric thermals

Atmospheric convection is both ubiquitous and fundamental to the climate system, as the primary means of communicating heat from the surface to the atmosphere. The fundamental building block of atmospheric convection seems to be "thermals", or isolated blobs of buoyant fluid which resemble expanding vortex rings. Thermals exhibit some surprising properties, however.  We present recent work focusing on dry thermals which  shows that i) dry thermals expand due to their buoyancy, not due to turbulent entrainment, ii)  their "virtual mass" effect can be described using an exact correspondence with the equations of magnetostatics, and iii) dry thermals experience negligible or even negative drag. We close by discussing the potential effects of moisture, and the many directions this opens for future work.