Investigating global stratospheric pollution from the 2006 Victorian bushfire using modern satellite data

Kane Stone
La Trobe University

Svetlana Petelina
La Trobe University

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     Last modified: July 29, 2011

Abstract
In December 2006, the state of Victoria suffered from a major bushfire season. On December 14th 2006, particularly large fire fronts ran across North-East Victoria and Gippsland resulting in a so-called pyro-cumulonimbus (PyroCB) event: large amounts of smoke aerosols were injected into the atmosphere up to unusually high altitudes above 12 km. The main focus of this work is to analyse the transport and evolution of this smoke plume, including its vertical and horizontal dispersion. We also demonstrate that, contrary to a present belief, part of the smoke plume was able to penetrate the tropopause and pollute the stratosphere at altitudes above 15 km. Limb-scattered spectral solar irradiance data measured by the Optical Spectrograph and Infrared Imaging System (OSIRIS) instrument onboard the Odin satellite are used for this purpose. Individual vertical limb radiance profiles, as well as monthly-averaged global maps of radiances at different altitudes, are being produced to track the smoke evolution in time and space. Different from tropospheric smoke aerosols whose lifetime is short due to effective removal mechanisms, stratospheric aerosols resulting from PyroCB events like this one can remain there for months. This is important to account for in global aerosol databases and in climate-related studies as such smoke aerosols absorb incoming and outgoing solar radiation and affect the Earth's global radiation budget and climate.