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

Abstract

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

Role of K-feldspar and quartz in global ice nucleation by mineral dust in mixed-phase clouds

“…For the present study, we use the global 3-dimensional chemistry-transport model TM4-ECPL (Daskalakis et al, 2016(Daskalakis et al, , 2022Myriokefalitakis et al, 2016Myriokefalitakis et al, , 2015Kanakidou et al, 2020) driven by ERA-interim reanalysis meteorological fields produced with the European Centre for Medium-Range Weather Forecasts (ECMWF) meteorological model (Dee et al, 2011). The specific model version has a horizontal resolution of 3 o longitude by 2 o latitude with 25 hybrid pressure vertical levels from surface up to 0.1hPa (about 65 km) and uses a model time step of 30 minutes.…”

A Coupled Evaluation of Operational MODIS and Model Aerosol Products for Maritime Environments Using Sun Photometry: Evaluation of the Fine and Coarse Mode

“…As noted in the introduction, fine mode particles are known to be long-lived and have been hypothesized by many to dominate maritime CCN budgets. In particular, biomass burning emissions and pollution from South America can result in long-lived fine mode aerosol transport of over nearly 10,000 [2,3,62]. Perhaps emission or physics need to be adjusted in models.…”

Effect of Synoptic‐Scale Dynamics on the Vertical Distribution of Tropospheric Ozone Over the Arabian Sea and the Indian Ocean During the Boreal Winter of 2018

“…Similar mid-tropospheric high ozone-low water vapor (HOLW) structures (the term "HOLW" for these structures is coined by Anderson et al (2016)) are repeatedly reported over the major Oceanic regions like Pacific Ocean, Atlantic and Indian Ocean by many researchers during several campaigns. Though a common causative mechanism for the formation of this layer cannot be assigned, as it varies depending on the location, time and background meteorology, several possible pathways are proposed; continental transport (e.g., Boylan et al, 2015), stratospheric intrusions and transport from mid-latitude UT (e.g., Hayashi et al, 2008;Tao et al, 2018;Zachariasse et al, 2000Zachariasse et al, , 2001, transport from biomass burning sites (e.g., Anderson et al, 2016;Taupin et al, 1999) or both stratospheric intrusions and transport from biomass burning locations or continents (e.g., Chatfield et al, 2007;Daskalakis et al, 2022;Weller et al, 1996).…”

“…Generally, in the marine region low ozone concentrations are expected due to the lower availability of precursors for production and increased destruction via OH and halogen photochemistry (Kley et al., 1996; Liu et al., 1983; Read et al., 2008; Sarwar et al., 2015). However, continental influence, long‐range transport and prevailing meteorological conditions can significantly affect the ozone distribution over the ocean (e.g., Anderson et al., 2016; Boylan et al., 2015; Daskalakis et al., 2022; Jenkins et al., 2008, 2015; Lelieveld et al., 2001 and references there in). This makes any in situ measurements of ozone over the oceanic region a valuable asset; as the scope of satellite‐borne observations over these regions are limited in their quality of data.…”