Transport and Variability of Tropospheric Ozone over Oceania and Southern Pacific during the 2019–20 Australian Bushfires

Abstract

The present study contributes to the scientific effort for a better understanding of the potential of the Australian biomass burning events to influence tropospheric trace gas abundances at the regional scale. In order to exclude the influence of the long-range transport of ozone precursors from biomass burning plumes originating from Southern America and Africa, the analysis of the Australian smoke plume has been driven over the period December 2019 to January 2020. This study uses satellite (IASI, MLS, MODIS, CALIOP) and ground-based (sun-photometer, FTIR, ozone radiosondes) observations. The highest values of aerosol optical depth (AOD) and carbon monoxide total columns are observed over Southern and Central Australia. Transport is responsible for the spatial and temporal distributions of aerosols and carbon monoxide over Australia, and also the transport of the smoke plume outside the continent. The dispersion of the tropospheric smoke plume over Oceania and Southern Pacific extends from tropical to extratropical latitudes. Ozone radiosonde measurements performed at Samoa (14.4°S, 170.6°W) and Lauder (45.0°S, 169.4°E) indicate an increase in mid-tropospheric ozone (6–9 km) (from 10% to 43%) linked to the Australian biomass burning plume. This increase in mid-tropospheric ozone induced by the transport of the smoke plume was found to be consistent with MLS observations over the tropical and extratropical latitudes. The smoke plume over the Southern Pacific was organized as a stretchable anticyclonic rolling which impacted the ozone variability in the tropical and subtropical upper-troposphere over Oceania. This is corroborated by the ozone profile measurements at Samoa which exhibit an enhanced ozone layer (29%) in the upper-troposphere. Our results suggest that the transport of Australian biomass burning plumes have significantly impacted the vertical distribution of ozone in the mid-troposphere southern tropical to extratropical latitudes during the 2019–20 extreme Australian bushfires.

Key challenges for tropospheric chemistry in the Southern Hemisphere

“…The 2019/2020 Australian fires resulted in a vast injection of CO 2 into the atmosphere (Byrne et al, 2021;van der Velde et al, 2021) and record-breaking aerosol optical depth levels in the Southern Hemisphere, with smoke injection into the stratosphere comparable to a volcanic eruption that impacted dynamical circulation and radiative balance (Khaykin et al, 2020;Fasullo et al, 2021;Hirsch and Koren, 2021). The fires had significant impacts on tropospheric composition including elevated CO and ozone over the Oceania and southern Pacific regions (Be `gue et al, 2021;John et al, 2021) as well as deposition into the Southern Ocean resulting in widespread phytoplankton blooms (Tang et al, 2021). Smoke from the fires caused some of the worst air pollution events on record in Australia, with large populations exposed to hazardous air quality over extended periods of time (Nguyen et al, 2021).…”

Ozone Trend Analysis in Natal (5.4°S, 35.4°W, Brazil) Using Multi-Linear Regression and Empirical Decomposition Methods over 22 Years of Observations

“…They showed that the tropospheric ozone reaches its maximum partial column (45 DU), and its highest ozone mixing ratio during spring (October), coinciding with the BB season, with impacts on the change of surface UV radiation by up to 10%. Bègue et al (2021) [10] examined the transport and variability of tropospheric ozone across Oceania and the South Pacific during the 2019-2020 Australian bushfires, demonstrating how major BB events affect tropospheric trace-gas abundance, particularly ozone, on a regional scale. Moreover, Khaykin et al (2020) [11] reported that these Australian bushfires spread over longer distances, with planetary-scale repercussions.…”