The Evolution of the Wave‐One Ozone Maximum During the 2017 LASIC Field Campaign at Ascension Island. Issue 10 (14th May 2021)

• Record Type: Journal Article
• Authors: Jenkins, Gregory S.; de Castro, Vagner; Cunha, Bruno; Fontanez, Ivan; Holzworth, Robert
• Is Part Of: Journal of geophysical research. Volume 126:Issue 10(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-05-14
• Subjects: biomass burning -- Ozone -- South Atlantic -- Southern Africa -- Wave One; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2020JD033972
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Aerosols associated with biomass burning sources in Southern Africa were the focus during the LASIC, CLARIFY, and ORACLES field intensives across the South Tropical Atlantic in August and September of 2017. During this period, we launched 20 ozonesondes to produce a high temporal resolution data set to complement the once per week regular ozonesondes to investigate episodes of elevated O3 mixing ratios from westward moving biomass burning from Southern Africa. Vertical profiles of tropospheric ozone reveal the presence of elevated ozone mixing ratios due to biomass burning in the lower to middle troposphere during this period. The collected data show ozone mixing ratios exceeded 80 ppb between 850 and 550 hPa when the origin of air was Southern Africa (Angola and regions to east). We also find elevated O3 mixing ratios in the 500–300 hPa layer, which could be linked to production of O3 via lightning (LNOX ) from deep convection over Africa, which is transported into the Southern Hemisphere by the Tropical Easterly Jet (TEJ). Low‐ozone mixing ratios in the lower troposphere are associated with transport from the Northern Tropical Atlantic, and there is evidence of pollution from South America. Surprisingly, we find limited observations of African Easterly Jet‐South (AEJ‐S) in its strong phase at Ascension Island, but elevated O3 mixing ratios are found when it does occur. Plain Language Summary: During the Southern Hemisphere dry season (June–November), fires are ubiquitous in Southern Africa leading the production of biomass burning aerosols, carbon monoxide, ozone, and methane, which are transported westward to the tropical Atlantic. As part of the LASIC field campaign, 20 ozonesondes are launched from Ascension Island to examine potential anthropogenic and natural sources of ozone between August 17 and 5 October 2017. Plumes of polluted air are observed at Ascension Island with values greater than 100 ppb in early September in the lower troposphere. Elevated ozone mixing ratios are also found in the upper troposphere which we attribute to thunderstorms producing Lightning NOX (LNOX ). Lightning locations are found north of the Equator over Africa, and LNOX produced ozone from these thunderstorms would be transported into the Southern Hemisphere via the Tropical Easterly Jet (TEJ). Key Points: Tropospheric ozone variability at Ascension Island during the LASIC, CLARIFY, and ORACLES field intensive is linked to biomass burning and continental lightning from Africa with additional influences from South America and the Tropical North and South Atlantic Ocean Biomass burning is responsible for elevated O3 mixing ratios between 850 and 500 hPa with values exceeding 120 ppb during the first week in September Ozonesonde data show coherence with CLARIFY aircraft data linking polluted aerosols layers and elevated O3 mixing ratios