Source: United States Navy
James Campbell, Ph.D., head of NRL’s Atmospheric Properties and Effects section, added “We are excited and proud to see David and his collaborative team awarded by NASA for the ground-breaking research that they’ve led into pyroCbs to date. The PYREX mission will address fundamental questions ranging from how day-to-day weather models predict extreme wildfire weather phenomena to how these smoke chimneys influence cloud formation, the chemical composition of the stratosphere and ultimately the climate.”
New observations of the Earth’s surface, wildfires, and atmospheric system will increase our understanding of complex phenomena in the global Earth system. PYREX has direct relevance to studies of atmospheric composition, weather and atmospheric dynamics, climate variability and change, the carbon cycle, and ecosystems. The experiment will improve understanding and predictive capability for changes in climate forcing and air quality associated with large wildfires, as well as the potential for climate feedbacks associated with increasing wildfire activity.
“The consequences from pyroCb smoke plumes observed in the lower stratosphere over the past ten years have created a significant knowledge gap,” said Dr. Peterson. “The onus now falls on the community to respond with field research that is dedicated to understanding pyroCbs and their impacts.”
The study will rely on multiple types of numerical models capturing different aspects of pyroCb science at different scales. The measurement components will make extensive use of models at fire-scale, coupled fire-weather, and regional composition and transport to derive flight plans and to target data collection. The mission will measure all parameters required for initialization of pyroCb smoke plumes in aerosol transport, chemistry, and climate models. The outcome of this mission will be an improved understanding of pyroCb phenomena that can be used to improve the fidelity of Earth system models in addition to those included in the PYREX study.
More than 140 pyroCb events were observed over Canada in 2023, far eclipsing any single year prior. The smoke released by pyroCbs in British Columbia, Yukon, and Alberta traveled far downwind, contributing strongly to air-quality and visibility hazards observed across the eastern United States, Canada, and even across the Atlantic. Combined with tragic fire-driven events in Hawaii and Greece, and a huge increase in North American fire activity on a decadal scale, it’s hard not to see the clear linkages between this activity and the warming climate overall.
PyroCbs are a result of the thermal buoyancy within a smoke plume, driven by the heat of the fire relative to the surrounding air. It is this fundamental process that determines the vertical limit of a rising plume, where smoke arrives in the atmosphere above the fire, and thus the downwind trajectory and lifetime of the smoke.
In some regions, like the tropics, smoke-plume-rise is damped by relatively low buoyancy, and the plumes typically do not reach high altitudes. In western North America, however, and other regions favorable to pyroCb development, the potential for plume rise is clearly significant. Measurements of detailed fire-smoke-weather processes are necessary to better understand pyroCb activity and smoke transport to the stratosphere.
The ramifications for understanding these initial stages of plume-driven dynamics will have equally long-lasting impacts on how we model fires of all scales and their downwind impacts on air quality and radiation. Global and regional-scale modeling of smoke transport is a decades-long endeavor that has never fully represented these important physical mechanisms in operational predictions.
The ability to accurately model smoke plume rise, from the surface to the lower stratosphere, will lead to consequential gains in forecast skill, both in terms of long-range smoke transport, surface air quality, feedbacks via light absorption, and impacts on clouds and weather. PYREX is not only timely, but fundamental toward a better understanding of fire and smoke for scientific research and operational prediction.
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