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- Title
Satellite Evidence of HONO/NO<sub>2</sub> Increase With Fire Radiative Power.
- Authors
Fredrickson, C. D.; Theys, N.; Thornton, J. A.
- Abstract
Wildfires are important sources of atmospheric reactive nitrogen. The reactive nitrogen species partitioning generally depends on fire characteristics. One reactive nitrogen compound, nitrous acid (HONO), is a source of hydroxyl radicals and nitric oxide, which can impact the oxidizing capacity of the atmosphere and fire plume chemistry and composition. We study the Australian wildfire season of 2019–2020, known as Black Summer, where numerous large and intense wildfires burned throughout the continent. We use HONO and nitrogen dioxide (NO2) from the TROPOspheric Monitoring Instrument (TROPOMI) and fire radiative power (FRP) from the Visible Infrared Imaging Radiometer Suite to investigate HONO and NO2 relationships with fire characteristics. The ratio of HONO to NO2 increases linearly with FRP both in Australia and globally. Both Australian and global fire relationships depend strongly on land cover type. These relationships can be applied to emission inventories to improve wildfire emission representation in models. Plain Language Summary: During the southern hemisphere summer from 2019 to 2020, colloquially known as the Black Summer, multiple wildfires burned throughout Australia that caused widespread environmental, ecological, and property damage. The smoke and gases from the wildfires contributed to poor air quality and impacted stratospheric ozone chemistry. One gas that wildfires emit is nitrous acid, a nitrogen‐containing molecule that breaks down under sunlight to create reactive species. These reactive species undergo rapid chemical transformations that ultimately lead to the creation of pollutants, such as ozone and particulate matter. Nitrous acid is emitted alongside nitrogen dioxide from wildfire smoke, but the amounts emitted depend on fire characteristics. Multiple satellites were able to measure nitrous acid, nitrogen dioxide, and fire power during the Black Summer. By counting each smoke pixel and computing summary statistics, we found an increasing, linear relationship between the ratio of nitrous acid to nitrogen dioxide and fire power. Satellites can also characterize the type of ecosystem that is burning. With this information, we derived relationships over three ecosystem types, which can be extended globally. This relationship can be included in computer models that simulate the chemistry of the atmosphere and the impacts of wildfire emissions. Key Points: We report TROPOspheric Monitoring Instrument nitrous acid, nitrogen dioxide, and the ratio of nitrous acid to nitrogen dioxide during the Australian Black SummerMean nitrous‐acid‐to‐nitrogen‐dioxide ratio shows an increasing relationship with mean fire radiative power both in Australia and globallyThe relationship between nitrous‐acid‐to‐nitrogen‐dioxide ratio and fire radiative power is affected by vegetation type
- Subjects
AUSTRALIA; WILDFIRES; SMOKE; REACTIVE nitrogen species; NITROUS acid; STRATOSPHERIC chemistry; OZONE layer; NITROGEN dioxide; EMISSION inventories
- Publication
Geophysical Research Letters, 2023, Vol 50, Issue 17, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2023GL103836