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.
Highlights
Biomass burning is a significant source of aerosols and active trace gases that impact the atmospheric composition from local to global scales, with consequences for tropospheric ozone production and budget
It is worth noting that the total column of carbon monoxide (TCO) anomalies obtained from ground-based measurements are observed during the transport events of Australian carbon monoxide (CO) plumes detected from Infrared Atmospheric Sounding Interferometer (IASI) observations (Figure 4a)
We presented the tropospheric ozone and CO variability over Oceania and the Southern Pacific during the 2019–20 Australian bushfires
Summary
Biomass burning is a significant source of aerosols and active trace gases that impact the atmospheric composition from local to global scales, with consequences for tropospheric ozone production and budget. Few studies on the influence of the smoke emissions from southeastern and eastern Australia on the tropospheric variability of aerosols and trace gases were undertaken [11,40,42,43] This is fairly surprising in view of the potential of biomass burning activity to change the physico-chemical composition in the troposphere at the local and regional scale [44,45]. Even though Kloss et al [40] showed that the Australian fire season of 2019–20 has already significantly impacted fire trace gas abundances in the southern hemisphere’s troposphere starting from September/October 2019, here we focus on the peak phase of the fire events (From December 2019 to January 2020) This is carried out to exclude the possible impact of ozone precursors from biomass burning plumes originating from Southern America and Africa [10].
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