On September 5, 2020, an extraordinary meteorological phenomenon occurred during the devastating Creek Fire in California. The fire grew so intense that it began to generate its own weather system, producing a towering pyrocumulonimbus cloud—a thunderhead formed from the intense heat and smoke of the wildfire itself. This phenomenon unleashed a barrage of lightning strikes that further fueled the already rampant flames, complicating firefighting efforts and highlighting the urgent need to understand these wildfire-induced storms. Known as pyrocumulonimbus clouds, these fire-borne weather systems have become a significant and increasingly frequent feature of wildfire seasons across the Western United States, profoundly affecting regional air quality, weather patterns, and ultimately, global climate processes.
Until recently, the scientific community had been unable to successfully simulate these pyrocumulonimbus events within comprehensive Earth system models due to their complex dynamics and the intricate interactions between fire emissions, atmospheric conditions, and terrain. This shortfall represented a critical gap in our ability to predict and mitigate the impacts of wildfires, especially as climate change exacerbates fire frequency and intensity worldwide. A groundbreaking study, published in Geophysical Research Letters on September 25, 2024, has now overcome these challenges by developing an innovative wildfire-Earth system modeling framework that accurately simulates the formation and behavior of pyrocumulonimbus clouds.
The research team, led by Dr. Ziming Ke of the Desert Research Institute (DRI), employed a combination of high-resolution wildfire emissions data, a one-dimensional plume-rise model, and explicit modeling of fire-induced water vapor transport within the Department of Energy’s Energy Exascale Earth System Model (E3SM). This integrative approach allowed the simulation to reproduce the timing, altitude, and intensity of the towering thunderhead generated during the Creek Fire, which NASA terms one of the largest pyrocumulonimbus clouds in US history. Further validation was achieved by replicating several storms formed during the 2021 Dixie Fire, demonstrating the model’s robustness under variable meteorological and fire conditions.
At the heart of this breakthrough is the recognition of how moisture transported vertically by terrain and wind contributes significantly to cloud development during extreme wildfire events. The wildfire plume not only emits smoke particles and heat but also injects considerable quantities of water vapor into the atmosphere, which interact with meteorological conditions to trigger deep convection resulting in thunderstorm formation. Accurately modeling this process requires capturing the complex feedback loops between the fire’s heat release, atmospheric dynamics, and microphysical cloud processes, all of which the newly developed framework successfully integrates.
Pyrocumulonimbus clouds inject vast amounts of aerosols and water vapor into the upper atmosphere, on par with emissions from small volcanic eruptions. These aerosols can persist in the stratosphere for months, significantly influencing atmospheric composition and radiative properties. As these particles and gases disperse globally, they affect Earth’s energy budget by altering how sunlight is absorbed and reflected. Particularly concerning is their transport to polar regions, where they modify cloud albedo and ozone chemistry, accelerating snow and ice melt. Such changes feed back into global climate systems, illustrating the far-reaching impact of these wildfire-induced storms.
Scientists estimate that between tens to hundreds of pyrocumulonimbus events occur globally each year, and this frequency is projected to rise as climate change intensifies wildfire activity. This growing occurrence heightens the urgency to incorporate these storms into Earth system models to better forecast their immediate meteorological effects and long-term impacts on atmospheric chemistry and climate feedback loops. Prior to this study, failure to account for pyrocumulonimbus clouds in climate simulations represented a significant blind spot in understanding the full ramifications of wildfires on global climate dynamics.
The interdisciplinary research team included collaborators from Lawrence Livermore National Laboratory, the University of California Irvine, and Pacific Northwest National Laboratory. By leveraging DOE’s E3SM framework, they were able to conduct simulations at an unprecedented resolution, capturing the intricate interactions between wildfire emissions, atmospheric convection, and moisture transport. This multiscale approach bridges the gap between local wildfire dynamics and broader Earth system processes, enabling new insights into the dual role of wildfires as both natural disasters and climate drivers.
Dr. Ke emphasized that the study is a pioneering step in integrating extreme wildfire phenomena into Earth system models, setting a foundation for future research to incorporate these storms into regional and global climate assessments. This advance enhances the scientific community’s capacity to anticipate wildfire behavior, improve preparedness for associated hazards such as lightning-induced fires and air pollution episodes, and inform policy decisions aimed at mitigating wildfires’ ecological and societal impacts.
Pyrocumulonimbus clouds represent a compelling example of how localized natural hazards can exert extensive influence on global systems. Their formation combines intense thermal dynamics from wildfires with atmospheric processes that bridge multiple scales, from plume rise to synoptic weather patterns. This research underscores the necessity of high-resolution models that capture such coupled processes, providing crucial insights for addressing the challenges posed by increasingly frequent and severe wildfires worldwide.
Moreover, by clarifying the role of pyrocumulonimbus clouds in atmospheric chemistry and climate feedbacks, these findings offer a critical lens through which to understand wildfire contributions to stratospheric aerosol populations, polar climate variability, and ozone layer dynamics. This enhanced understanding may also shed light on historical climate variability linked to wildfire activity and inform projections under future warming scenarios.
Ultimately, the newly developed wildfire-Earth system modeling framework marks a transformative advance in Earth system science. It not only fills a longstanding knowledge gap but demonstrates the power of integrating multiple scientific disciplines—ranging from fire ecology and meteorology to atmospheric chemistry and climate science—to tackle complex environmental challenges. As wildfires continue to grow in scale and intensity, such integrative research will be indispensable for safeguarding ecosystems, public health, and the climate system at large.
Subject of Research: Simulation of pyrocumulonimbus clouds and wildfire-atmosphere interactions in Earth system modeling.
Article Title: Simulating Pyrocumulonimbus Clouds Using a Multiscale Wildfire Simulation Framework
News Publication Date: 25-Sep-2024
Web References:
- https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024GL114025
- https://e3sm.org/
- https://www.dri.edu/
- https://www.nasa.gov/missions/suomi-npp/californias-creek-fire-creates-its-own-pyrocumulonimbus-cloud/
References:
Ke, Z., Tang, Q., Zhang, J., Chen, Y., Randerson, J., Li, J., & Zhang, Y. (2024). Simulating Pyrocumulonimbus Clouds Using a Multiscale Wildfire Simulation Framework. Geophysical Research Letters. https://doi.org/10.1029/2024GL114025
Image Credits: NASA
Keywords: Wildfires, Pyrocumulonimbus Clouds, Earth System Modeling, Atmospheric Chemistry, Climate Feedbacks, Energy Exascale Earth System Model, Fire-Induced Thunderstorms, Stratospheric Aerosols, Climate Change, Fire-Atmosphere Interactions, High-Resolution Simulation, Extreme Weather
