Latent Heating Is Required for Firestorm Plumes to Reach the Stratosphere

Abstract

City‐wide firestorms produce extreme convective plumes that loft soot into the atmosphere. If emplaced in the stratosphere, soot has long‐lasting impacts on global climate. Given the extreme sensible heating from the fire, the importance of additional heating from condensation is unclear and a subject of debate. Analytic plume calculations presented here establish that an idealized dry plume requires a temperature anomaly of at least 60 K at the top of the boundary‐layer to remain buoyant up to the cold‐point tropopause. Direct numerical and large‐eddy simulations indicate that dry firestorm plumes possess temperature anomalies that are less than the requirements for stratospheric ascent by a factor of two or more. In contrast, moist firestorm plumes are shown to reach the stratosphere by tapping into the abundant latent heat present in a moist environment. Latent heating is found to be essential to plume rise, raising doubts about the applicability of past work that neglected moisture.

Anthropocene Under Dark Skies: The Compounding Effects of Nuclear Winter and Overstepped Planetary Boundaries

“…An average person's life will dramatically change overnight. Many major cities could go up blazing in a firestorm, delivering large quantities of soot into the upper atmosphere (1,2) and killing millions (3). This will change the climate globally (2).…”