Convective available potential energy for pyrocumulus: quantifying the effect of CO2 emissions from combustion

Abstract:

Pyrocumulus are among the most spectacular extreme weather phenomena and can influence local-scale atmospheric circulations in life-threatening ways. The combustion of wildfires generates heat and releases water vapor, which have both been assessed in numerical simulations and in calculations of convective available potential energy (CAPE). Carbon dioxide (CO₂) is an additional combustion product that alters the atmospheric composition. Here, we present a quantification of CO₂'s role in changing CAPE. CO₂ has a higher molecular weight than dry air and therefore reduces a parcel's buoyancy. The isolated effect of the additional CO₂ from combustion is then to decrease CAPE. We assess the magnitude of this CAPE decrease using reanalysis soundings, focusing on the conditions of the January 2020 Australian fires.