Exploring the effects of wildfires on stratospheric aerosol composition and dynamics using satellite and ground-based lidars
Résumé
The severity of wildfires has remarkably increased over the last years in both Northern
and Southern hemispheres and there is an emerging realization of their effect on climate and
ozone layer. Intense wildfires give rise to extreme thunderstorms termed PyroCb, which can
inject significant amounts of smoke into the stratosphere. A number of recent studies have
demonstarted that the effects of strong PyroCb outbreaks on the global stratosphere can rival
those of moderate volcanic eruptions in terms of magnitude and duration whilst exceeding
them in terms of radiative forcing. Furthermore, the PyroCb injections into the stratosphere
were shown to generate persistent synoptic-scale anticyclones (SCV – Smoke-Charged
Vortex), lofting confined bubbles of smoke deep into the stratosphere due to solar heating of
carbonaceous aerosols, which prolongs their atmospheric residence time and radiative
effects.
Here we exploit a synergy of satellite and ground-based lidar observations to characterize
the impact of PyroCb on the stratospheric aerosol composition and dynamics. We use
CALIOP observations of aerosol backscatter and depolarization to characterize the optical
properties of stratospheric smoke aerosols, their evolution and longevity. Additionally, we
use multi-decade aerosol lidar records at the French Observatoire de Haute Provence (43.9
N) and Lauder observatory in New Zealand (45.0 S), both located downwind of the main
sources of PyroCb activity. Using the long-term ground-based and satellite lidar
observations of depolarization, we point out the longevity of fine smoke particles in the
stratosphere.
The multi-wavelength fluorescence lidar observations at the French LILAS site are used
to constrain the optical properties of stratospheric smoke plumes, which provides an
accurate reference for estimating the radiative forcing of persistent smoke plumes in the
stratosphere.
Finally, the global wind profiling, exclusively provided by Aeolus Doppler lidar, is used
to explore the dynamics of the rotating smoke plumes and related generation of downward-
propagating gravity waves