Discovery of smoke-charged vortices generated by wildfires
A new type of atmospheric disturbance, comparable in magnitude to volcanic plumes, was discovered following the Australian forest fires in early 2020. The presence of ash plumes rising into the atmosphere by convection after different fires had previously been identified by satellite observations, but was only considered as a trace of the initial ash cloud.
Although the European meteorological model (ECMWF) does not take into account the effect of aerosols it is indirectly, through its reanalyses of ozone, vorticity and temperature that the structure of this cloud has been followed and analysed. The vorticity trend, i.e. the measurement of the rotation of an air parcel, is an essential element for understanding the behaviour of these ash clouds. Maintained by a vertical temperature dipole within the cloud, it keeps the organic carbon particles confined giving it a certain stability. This enabled the cloud to circumnavigate the Earth more than once in the southern hemisphere in about 12 weeks.
Following this discovery, one of the interrogations was to know if this was the first time this event had occurred. This question led to a research effort that focused on developing computer tools to hunt for these ash vortexes on previous forest fires. The second largest of the decade was a Canadian fire in the summer of 2017. The cloud hunt was successful as this project identified three ash vortexes emanating from the same fire that had different trajectories on either side of the Northern Hemisphere.
The consequences of this type of event are diverse (effects on the climate, hole in the ozone layer, etc.) and it is important to be concerned about them, as climate models predict an increase in the frequency and magnitude of forest fires in the context of global warming.
Smoke-charged vortices in the stratosphere generated by wildfires and their behaviour in both hemispheres: comparing Australia 2020 to Canada 2017. Hugo Lestrelin, Bernard Legras, Aurélien Podglajen, and Mikail Salihoglu. Atmos. Chem. Phys., 21, 7113–7134, 2021. https://doi.org/10.5194/acp-21-7113-2021 • https://acp.copernicus.org/articles/21/7113/2021/