A three dimensional Lagrangian analysis of the smoke plume from the
2019/2020 Australian wildfire event
Abstract
During the 2019/2020 bushfire season in Australia a rising plume, which
had record concentration of smoke in the lower Stratosphere, was
generated by the intense wildfires in southeast Australia. In this
paper, we use the atmospheric wind reanalysis model ERA5 to characterize
the three dimensional atmospheric transport in the region following a
dynamical system approach in the Lagrangian framework. Aided by the
Finite Time Lyapunov Exponent tool (FTLE) we identify Lagrangian
Coherent Structures which simplify the three-dimensional transport
description and make possible the characterization of the smoke plume
evolution. Different reduced FTLE formulations are compared to study the
impact of the vertical velocity and the vertical shear on the movement
of the plume. Several examples of the LCS geometries are described and
we show the presence of 3D lobe dynamics at play. Also, we unveil the
qualitatively different dynamical fates of the smoke parcels
trajectories depending on the region in which they originated.
Transport paths obtained with the inclusion of the buoyancy effects are
compared with those obtained considering only the reanalysis velocity.