LAUSR

Pyrocumulonimbus (pyroCb) are wildfire-generated convective clouds that can inject smoke directly into the stratosphere. PyroCb have been tracked for years, yet their apparent rarity and episodic nature lead to highly uncertain climate impacts. In situ measurements of pyroCb smoke reveal its distinctive and exceptionally stable aerosol properties and define the long-term influence of pyroCb activity on the stratospheric aerosol budget. Analysis of 13 years of airborne observations shows that pyroCb are responsible for 10 to 25% of the black carbon and organic aerosols in the “present-day” lower stratosphere, with similar impacts in both the North and South Hemispheres. These results suggest that, should pyroCb increase in frequency and/or magnitude in future climates, they could generate dominant trends in stratospheric aerosol. Description Fired up Large wildfires can generate pyrocumulonimbus clouds that transport smoke into the stratosphere and have major impacts on the stratospheric aerosol budget and climate. Katich et al. analyzed 13 years of airborne observations to determine the chemical and physical compositions of pyrocumulonimbus smoke and to quantify its effects on stratospheric aerosols. These clouds are responsible for as much as 25% of the black carbon and organic aerosols now in the lower stratosphere and may become an even more important influence on future climate as the frequency and severity of extreme fires increase. —HJS The fingerprint of pyrocumulonimbus clouds can be seen in lower stratospheric aerosols.