Evidence of the cloud lifetime effect from wildfire‐induced thunderstorms

A case study is presented of pyro‐cumulonimbi (pyroCbs) forming over Canadian forest fires. Cloud‐top ice effective radius values of these pyroCbs are significantly smaller than are those within surrounding convection. The smoke provides a massive source of cloud condensation nuclei (CCN), resulting in smaller cloud droplets which freeze homogeneously at temperatures around −40°C and produce very small ice crystals. It is also shown that the pyroCb anvils persist 6–12 hours longer than convectively‐generated cirrus anvils from nearby convection. This provides evidence for the so‐called cloud lifetime effect, an aerosol indirect effect identified by the most recent Intergovernmental Panel on Climate Change (IPCC) report.