Impact of biomass burning and stratospheric intrusions in the remote South Pacific Ocean troposphere

Abstract. The ozone mixing ratio spatiotemporal variability in the pristine South Pacific Ocean is studied, for first time, using 21-year-long (O3) records from entire southern tropical and subtropical between 1994 2014. analysis considered regional O3 vertical observations ozonesondes, surface carbon monoxide (CO) flasks, three-dimensional chemistry-transport model simulations of global troposphere. Two numerical simulations, with without biomass burning emissions, were performed to disentangle importance relative stratospheric intrusions ambient levels region. Tagged tracers stratosphere CO various regions have been used track impact these different on levels. Patterns analyzed based atmospheric dynamics variability. Considering interannual observations, can capture observed gradients troposphere a positive bias 7.5 % upper troposphere/lower (UTLS) as well near surface. Remarkably, even most region ocean affected by distant emissions convective outflow through mid high subsequent subsidence over oceanic Therefore, contribution tropospheric maximizes UTLS. Southeast Asian open fires identified major contributing source Pacific, average study period about 8.5 13 ppbv at Rapa Nui Samoa, respectively, an altitude around 12 km during season spring Southern Hemisphere. America second-most important that influences area. Its lower (6.5 3.8 Samoa). All sources contribute 15–23 Samoa account 25 total Pacific. This also seen O3, which precursor only few period, while stratosphere–troposphere exchange Ocean, 15–20 subtropics.