Description
Wildfires are increasingly recognized as fully coupled land–atmosphere systems that produce complex meteorological feedbacks, including the generation of deep convective clouds known as pyrocumulonimbus (pyroCb). While most wildfires produce shallow boundary-layer smoke plumes, extreme events can generate buoyant, fire-driven updrafts that rise into the troposphere and, in severe cases, penetrate above the tropopause, injecting smoke into the lower stratosphere where it can persist for months. These phenomena have significant implications for climate, air quality, and operational fire management, yet the environmental conditions that distinguish pyroCb-producing fires from those that do not remain underinvestigated.
PyroCb formation results from nonlinear interactions among fire heat release, plume thermodynamics, and the surrounding atmosphere. Although wildfires generate substantial sensible heat fluxes that enhance plume buoyancy, the development of these plumes is strongly influenced by environmental factors such as convective available potential energy (CAPE), convective inhibition (CIN), mid-level moisture, vertical wind shear, and entrainment processes. Previous research indicates that pyroCb events can occur in environments with only modest instability compared to typical severe thunderstorms, indicating that fire-induced heating may compensate for marginal atmospheric conditions. Nevertheless, the relative importance and interplay of these environmental controls remain uncertain.
This study investigates the atmospheric conditions governing pyroCb initiation and development, focusing on two central questions: (1) how variations in thermodynamic structure, particularly CAPE, CIN, and mid-level humidity, modulate the transition from a buoyant fire plume to deep convection, and (2) how vertical wind shear interacts with plume entrainment and fire-driven buoyancy to sustain or suppress organized pyroCb updrafts. By improving the understanding of these processes, this work aims to enhance the prediction of extreme wildfire-driven convection as wildfire intensity and frequency continue to increase.