scholarly journals Ozone seasonal evolution and photochemical production regime in polluted troposphere in eastern China derived from high resolution FTS observations

2017 ◽  
Author(s):  
Youwen Sun ◽  
Cheng Liu ◽  
Mathias Palm ◽  
Corinne Vigouroux ◽  
Qihou Hu ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Meteorological Data ◽  
Eastern China ◽  
Ozone Production ◽  
Ozone Pollution ◽  
Seasonal Evolution ◽  
Photochemical Production ◽  
Production Regime ◽  
Autumn And Winter ◽  
Ozone Levels

Abstract. A precise knowledge of ozone seasonal evolution and photochemical production regime in polluted troposphere in China has important policy implications for ozone pollution controls especially in megacities where ozone pollution is common throughout the year. In this study, we used tropospheric ozone, CO and HCHO columns derived from high resolution Fourier transform infrared spectrometry (FTS) in Hefei, China, tropospheric NO2 columns deduced from overpass Ozone Monitoring Instrument (OMI), surface meteorological data, and a back trajectory cluster analysis technique to investigate ozone seasonal evolution and photochemical production regime in eastern China from 2014–2017. A pronounced seasonal cycle for tropospheric ozone is captured by FTS, where high levels of tropospheric ozone occurs in spring and summer, and low levels of tropospheric ozone occurs in autumn and winter. Day-to-day variations in spring and summer are in most cases larger than those in autumn and winter. At the same time, it shows that the tropospheric ozone roughly increases over time at the first half year and reaches the maximum in June, and then it decreases over time at the second half year. Tropospheric ozone columns in June are, on average, 0.5×1018 molecules*cm−2 (47.6 %) higher than those in December which has a mean value of 1.05×1018 molecules*cm−2. The OMI time series shows similar behaviour. The measured features can basically be reproduced by GEOS-Chem and WRF-Chem data but with slight shifts in the timing of the seasonal maximum. Back trajectories analysis shows that: air pollutions in megacities in central-southern China, northwest China, and the key pollution area, i.e., Yangtze River Delta area in eastern China, dominates the contributions to the observed tropospheric ozone levels, while the contributions from the other two key pollution areas, i.e., Beijing-Tianjin-Hebei in north China and Pearl River Delta in south China, are very small; Air masses generated from polluted areas have more transportations to the observed area in spring and summer than in autumn and winter, and hence have more contributions to the observed tropospheric ozone levels. Correlations between tropospheric ozone and meteorological data disclosed that spring and summer is more favorable to photochemical ozone production than in autumn and winter. Finally, the HCHO/NO2 ratio is used as a proxy to investigate the chemical sensitivity of ozone production (PO3). The results show that the PO3 is mainly NOx limited in summer, while it is mainly VOC or mix VOC-NOx limited in winter. Statistics show that NOx limited, mix VOC-NOx limited, and VOC limited PO3 accounts for 60.1 %, 28.7 %, and 11 %, respectively.

scholarly journals Ozone seasonal evolution and photochemical production regime in the polluted troposphere in eastern China derived from high-resolution Fourier transform spectrometry (FTS) observations

2018 ◽  
Vol 18 (19) ◽  
pp. 14569-14583 ◽  
Author(s):  
Youwen Sun ◽  
Cheng Liu ◽  
Mathias Palm ◽  
Corinne Vigouroux ◽  
Justus Notholt ◽  
...  
Keyword(s):  
Fourier Transform ◽  
High Resolution ◽  
Meteorological Data ◽  
Eastern China ◽  
Back Trajectory ◽  
Seasonal Evolution ◽  
Fourier Transform Spectrometry ◽  
Photochemical Production ◽  
Production Regime ◽  
Tropospheric O3

Abstract. The seasonal evolution of O3 and its photochemical production regime in a polluted region of eastern China between 2014 and 2017 has been investigated using observations. We used tropospheric ozone (O3), carbon monoxide (CO), and formaldehyde (HCHO, a marker of VOCs (volatile organic compounds)) partial columns derived from high-resolution Fourier transform spectrometry (FTS); tropospheric nitrogen dioxide (NO2, a marker of NOx (nitrogen oxides)) partial column deduced from the Ozone Monitoring Instrument (OMI); surface meteorological data; and a back trajectory cluster analysis technique. A broad O3 maximum during both spring and summer (MAM/JJA) is observed; the day-to-day variations in MAM/JJA are generally larger than those in autumn and winter (SON/DJF). Tropospheric O3 columns in June are 1.55×1018 molecules cm−2 (56 DU (Dobson units)), and in December they are 1.05×1018 molecules cm−2 (39 DU). Tropospheric O3 columns in June were ∼50 % higher than those in December. Compared with the SON/DJF season, the observed tropospheric O3 levels in MAM/JJA are more influenced by the transport of air masses from densely populated and industrialized areas, and the high O3 level and variability in MAM/JJA is determined by the photochemical O3 production. The tropospheric-column HCHO∕NO2 ratio is used as a proxy to investigate the photochemical O3 production rate (PO3). The results show that the PO3 is mainly nitrogen oxide (NOx) limited in MAM/JJA, while it is mainly VOC or mixed VOC–NOx limited in SON/DJF. Statistics show that NOx-limited, mixed VOC–NOx-limited, and VOC-limited PO3 accounts for 60.1 %, 28.7 %, and 11 % of days, respectively. Considering most of PO3 is NOx limited or mixed VOC–NOx limited, reductions in NOx would reduce O3 pollution in eastern China.

Unexpected Fast Monoterpene Oxidation In Eastern China

2021 ◽  
Author(s):  
Haichao Wang
Keyword(s):  
Eastern China ◽  
Field Measurements ◽  
Ozone Production ◽  
Nitrate Radical ◽  
Peroxy Radicals ◽  
Ozone Pollution ◽  
Volatile Organic ◽  
Secondary Aerosols ◽  
Photochemical Ozone

<p>Monoterpene plays an important role in the formation of secondary aerosols and ozone in the troposphere. However, the field characterization of monoterpene chemistry in ozone pollution is still very sparse. Here we report fast daytime oxidation of monoterpene by hydroxyl radical, nitrate radical and ozone based on field measurements in Eastern China. We find fast monoterpene oxidation produces peroxy radicals efficiently and enhances the photochemical ozone production largely with an additional 8.6 ppb of ozone production per day on average (14%), whose effect was even more important than that of isoprene chemistry in the analyzed dataset. We propose that the reduction of anthropogenic volatile organic compounds should be much more stringent in the presence of high monoterpenes to alleviating ozone pollution.</p>

scholarly journals Global distribution of tropospheric ozone from satellite measurements using the empirically corrected tropospheric ozone residual technique: Identification of the regional aspects of air pollution

2003 ◽  
Vol 3 (4) ◽  
pp. 893-907 ◽  
Author(s):  
J. Fishman ◽  
A. E. Wozniak ◽  
J. K. Creilson
Keyword(s):  
Tropospheric Ozone ◽  
Total Ozone ◽  
Stratospheric Ozone ◽  
Eastern China ◽  
Daily Basis ◽  
Stratospheric Aerosol ◽  
Eastern United States ◽  
Ozone Pollution ◽  
Austral Spring ◽  
Data Set

Abstract. Using coincident observations of total ozone from the Total Ozone Mapping Spectrometer (TOMS) and stratospheric ozone profiles from the Solar Backscattered Ultraviolet (SBUV) instruments, detailed maps of tropospheric ozone have been derived on a daily basis over a time period spanning more than two decades. The resultant climatological seasonal depictions of the tropospheric ozone residual (TOR) show much more detail than an earlier analysis that had used coincident TOMS and Stratospheric Aerosol and Gas Experiment (SAGE) ozone profiles, although there are many similarities between the TOMS/SAGE TOR and the TOMS/SBUV TOR climatologies. In particular, both TOR seasonal depictions show large enhancements in the southern tropics and subtropics in austral spring and at northern temperate latitudes during the summer. The much greater detail in this new data set clearly defines the regional aspect of tropospheric ozone pollution in northeastern India, eastern United States, eastern China, and west and southern Africa. Being able to define monthly climatologies for each year of the data record provides enough temporal resolution to illustrate significant interannual variability in some of these regions.

scholarly journals Transboundary ozone pollution across East Asia: daily evolution and photochemical production analysed by IASI+GOME2 multispectral satellite observations and models

2017 ◽  
Author(s):  
Juan Cuesta ◽  
Yugo Kanaya ◽  
Masayuki Takigawa ◽  
Gaëlle Dufour ◽  
Maxim Eremenko ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
East Asia ◽  
Satellite Data ◽  
Tropospheric Ozone ◽  
Northern China ◽  
Satellite Observations ◽  
The Yellow Sea ◽  
Ozone Pollution ◽  
Photochemical Production ◽  
Pollution Plumes

Abstract. We characterize a transboundary ozone pollution outbreak transported across East Asia in early May 2009 using new multispectral satellite observations of lowermost tropospheric ozone in synergy with other satellite data and models. Our analysis is focused on the daily evolution of ozone pollution plumes initially formed over the North China Plain (NCP) and their transport pathways over Northern China, Korea, Japan and the surrounding seas. A main aspect of the study is an estimation of the contribution of photochemical production of ozone along transport using the ratio of ozone to carbon monoxide enhancements with respect to background levels derived from satellite data and also from chemistry-transport models. A key contribution of the analysis is the use of new satellite data offering unprecedented skills to observe the horizontal distribution of lowermost tropospheric ozone over East Asia on daily basis, with a multispectral approach called IASI+GOME2. These satellite observations are in good agreement with ozonesondes, with low mean biases (3 %), a precision of about 16 %, a correlation coefficient of 0.85 and practically the same standard deviation for a comparison based on 2 years of data from 46 launching stations distributed worldwide, during all seasons. A similar agreement is also found over East Asia. Moreover, IASI+GOME2 offers a unique capacity for observing the evolution of near surface ozone during pollution outbreaks (with 5 % bias and 0.69 correlation), according to a comparison with surface in situ measurements during 2 major ozone events over several Japanese Islands. Single-band ozone retrievals, as those from IASI in the thermal infrared, do not capture such variability. Using IASI+GOME2, we put in evidence that (i) ozone pollution plumes are transported by an anticyclonic circulation around the Yellow Sea from the NCP to Northern China, Korea and Japan, co-located with carbon monoxide plumes, (ii) over Northern China the plume splits into two pollution filaments with one mixing with freshly emitted pollutants and (iii) ozone is produced every day of the event accounting for an enhancement in concentration during transport across East Asia of up to ∼ 84 % with respect to that produced over NCP. This estimation is done according to monotonically increasing values during 7 days of the ratio of ozone to carbon monoxide enhancements within the transported pollution plumes from about ∼ 0.25 over the NCP to ∼ 0.46 over the Pacific south of Japan.

scholarly journals Photochemical environment over Southeast Asia primed for hazardous ozone levels with influx of nitrogen oxides from seasonal biomass burning

2020 ◽  
Author(s):  
Margaret R. Marvin ◽  
Paul I. Palmer ◽  
Barry G. Latter ◽  
Richard Siddans ◽  
Brian J. Kerridge ◽  
...  
Keyword(s):  
Nitrogen Oxides ◽  
Southeast Asia ◽  
Biomass Burning ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Transport Model ◽  
Dry Season ◽  
Ozone Exposure ◽  
Ozone Production ◽  
Ozone Levels

Abstract. Mainland and maritime Southeast Asia are home to more than 655 million people, representing nearly 10 % of the global population. The dry season in this region is typically associated with intense biomass burning activity, which leads to a significant increase in surface air pollutants that are harmful to human health, including ozone (O3). Latitude-based differences in dry season and land use distinguish two regional biomass burning regimes: (1) burning on the peninsular mainland peaking in March and (2) burning across Indonesia peaking in September. The type and amount of material burned in each regime impacts the emissions of nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs), which combine to produce ozone. Here, we use the nested GEOS-Chem atmospheric chemistry transport model (horizontal resolution of 0.25° × 0.3125°), in combination with satellite observations from the Ozone Monitoring Instrument (OMI) and ground-based observations from Malaysia, to investigate ozone photochemistry over Southeast Asia in 2014. Seasonal cycles of tropospheric ozone columns from OMI and GEOS-Chem peak with biomass burning emissions. Compared to OMI, the model has a mean annual bias of −11 % but tends to overestimate tropospheric ozone near areas of seasonal fire activity. We find that outside of these burning areas, the underlying photochemical environment is generally NOx-limited, dominated by anthropogenic NOx and biogenic non-methane VOC emissions. Pyrogenic emissions of NOx play a key role in photochemistry, shifting towards more VOC-limited ozone production and contributing about 30 % of the regional ozone formation potential during both biomass burning seasons. Using the GEOS-Chem model, we find that biomass burning activity coincides with widespread ozone exposure at levels that exceed world public health guidelines, resulting in 272 premature deaths on mainland Southeast Asia in March of 2014 and another 273 deaths across Indonesia in September. Despite a positive model bias, hazardous ozone levels are confirmed by surface observations during both burning seasons.

scholarly journals Transboundary ozone pollution across East Asia: daily evolution and photochemical production analysed by IASI + GOME2 multispectral satellite observations and models

2018 ◽  
Vol 18 (13) ◽  
pp. 9499-9525 ◽  
Author(s):  
Juan Cuesta ◽  
Yugo Kanaya ◽  
Masayuki Takigawa ◽  
Gaëlle Dufour ◽  
Maxim Eremenko ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
East Asia ◽  
Satellite Data ◽  
Tropospheric Ozone ◽  
Northern China ◽  
Satellite Observations ◽  
The Yellow Sea ◽  
Ozone Pollution ◽  
Photochemical Production ◽  
Pollution Plumes

Abstract. We characterise a transboundary ozone pollution outbreak transported across East Asia in early May 2009 using new multispectral satellite observations of lowermost tropospheric ozone (located below 3 km altitude) in synergy with other satellite data and models. Our analysis is focused on the daily evolution of ozone pollution plumes initially formed over the North China Plain (NCP) and their transport pathways over northern China, Korea, Japan and the surrounding seas. A main aspect of the study is an estimation of the contribution of photochemical production of ozone during transport using the ratio of ozone to carbon monoxide enhancements with respect to background levels derived from satellite data and also from chemistry–transport models.A key contribution of the analysis is the use of new satellite data offering unprecedented skills to observe the horizontal distribution of lowermost tropospheric ozone over East Asia on a daily basis, with a multispectral approach called IASI + GOME2 (combining Infrared Atmospheric Sounding Interferometer observations in the IR and Global Ozone Monitoring Experiment-2 measurements in the UV). These satellite observations are in good agreement with ozonesondes, with low mean biases (3 %), a precision of about 16 %, a correlation coefficient of 0.85 and practically the same standard deviation for a comparison based on 2 years of data from 46 launching stations distributed worldwide, during all seasons. A similar agreement is also found over East Asia. Moreover, IASI + GOME2 offers a unique capacity for observing the evolution of near-surface ozone during pollution outbreaks (with 5 % bias and 0.69 correlation), according to a comparison with surface in situ measurements during two major ozone events over several Japanese islands. Single-band ozone retrievals, such as those from IASI in the thermal infrared, do not capture such variability.Using IASI + GOME2, we show that (i) ozone pollution plumes are transported by an anticyclonic circulation around the Yellow Sea from the NCP to northern China, Korea and Japan, collocated with carbon monoxide plumes; (ii) over northern China the plume splits into two pollution filaments with one mixing with freshly emitted pollutants; and (iii) ozone is produced every day of the event, accounting for an enhancement in concentration during transport across East Asia of up to  ∼ 84 % with respect to that produced over NCP. This estimation is done according to monotonically increasing values during 7 days of the ratio of ozone to carbon monoxide enhancements within the transported pollution plumes from about  ∼ 0.25 over the NCP to  ∼ 0.46 over the Pacific south of Japan.

scholarly journals Impact of climate change on tropospheric ozone and its global budgets

2008 ◽  
Vol 8 (2) ◽  
pp. 369-387 ◽  
Author(s):  
G. Zeng ◽  
J. A. Pyle ◽  
P. J. Young
Keyword(s):  
Climate Change ◽  
Tropospheric Ozone ◽  
Climate Model ◽  
Surface Ozone ◽  
Lower Troposphere ◽  
Ozone Production ◽  
Anthropogenic Emissions ◽  
Free Troposphere ◽  
Tropical Ocean ◽  
Ozone Levels

Abstract. We present the chemistry-climate model UMCAM in which a relatively detailed tropospheric chemical module has been incorporated into the UK Met Office's Unified Model version 4.5. We obtain good agreements between the modelled ozone/nitrogen species and a range of observations including surface ozone measurements, ozone sonde data, and some aircraft campaigns. Four 2100 calculations assess model responses to projected changes of anthropogenic emissions (SRES A2), climate change (due to doubling CO2), and idealised climate change-associated changes in biogenic emissions (i.e. 50% increase of isoprene emission and doubling emissions of soil-NOx). The global tropospheric ozone burden increases significantly for all the 2100 A2 simulations, with the largest response caused by the increase of anthropogenic emissions. Climate change has diverse impacts on O3 and its budgets through changes in circulation and meteorological variables. Increased water vapour causes a substantial ozone reduction especially in the tropical lower troposphere (>10 ppbv reduction over the tropical ocean). On the other hand, an enhanced stratosphere-troposphere exchange of ozone, which increases by 80% due to doubling CO2, contributes to ozone increases in the extratropical free troposphere which subsequently propagate to the surface. Projected higher temperatures favour ozone chemical production and PAN decomposition which lead to high surface ozone levels in certain regions. Enhanced convection transports ozone precursors more rapidly out of the boundary layer resulting in an increase of ozone production in the free troposphere. Lightning-produced NOx increases by about 22% in the doubled CO2 climate and contributes to ozone production. The response to the increase of isoprene emissions shows that the change of ozone is largely determined by background NOx levels: high NOx environment increases ozone production; isoprene emitting regions with low NOx levels see local ozone decreases, and increase of ozone levels in the remote region due to the influence of PAN chemistry. The calculated ozone changes in response to a 50% increase of isoprene emissions are in the range of between −8 ppbv to 6 ppbv. Doubling soil-NOx emissions will increase tropospheric ozone considerably, with up to 5 ppbv in source regions.

scholarly journals Trends and Variability of Ozone Pollution over the Mountain-Basin Areas in Sichuan Province during 2013–2020: Synoptic Impacts and Formation Regimes

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1557
Author(s):  
Youfan Chen ◽  
Han Han ◽  
Murong Zhang ◽  
Yuanhong Zhao ◽  
Yipeng Huang ◽  
...  
Keyword(s):  
High Pressure ◽  
Surface Ozone ◽  
Emission Control ◽  
Warm Season ◽  
Sichuan Province ◽  
Ozone Production ◽  
Daily Maximum ◽  
Ozone Pollution ◽  
Reanalysis Dataset ◽  
Ozone Levels

Sichuan Province, the most industrialized and populated region in southwestern China, has been experiencing severe ozone pollution in the boreal warm season (April–September). With a surface ozone monitoring network and reanalysis dataset, we find that nearly all cities in Sichuan Province showed positive increasing trends in the warm-season ozone levels. The warm-season daily maximum 8-h average (MDA8) ozone levels increased by 2.0 ppb (4.8%) year−1 as a whole, with slightly larger trends in some sites such as a site in Zigong (5.2 ppb year−1). Seasonally, the monthly ozone level in Sichuan peaks from May to August (varies with year). The predominant warm-season synoptic patterns were objectively identified based on concurrent hourly meteorological fields from ERA5. High-pressure systems promote ozone production and result in high ozone concentrations, due to strong solar radiation as well as hot and dry atmospheric conditions. The increased occurrence of high-pressure patterns probably drives the ozone increase in Sichuan. When ozone pollution is relatively weak (with MDA8 ozone around 170 μg m−3), the air quality standard could be achieved in the short term by a 25% reduction of NOx and VOCs emissions. Strengthened emission control is needed when ozone pollution is more severe. Our study provides implications for effective emission control of ozone pollution in Sichuan.

scholarly journals Impact of climate change on tropospheric ozone and its global budgets

2007 ◽  
Vol 7 (4) ◽  
pp. 11141-11189 ◽  
Author(s):  
G. Zeng ◽  
J. A. Pyle ◽  
P. J. Young
Keyword(s):  
Climate Change ◽  
Tropospheric Ozone ◽  
Climate Model ◽  
Surface Ozone ◽  
Lower Troposphere ◽  
Ozone Production ◽  
Anthropogenic Emissions ◽  
Free Troposphere ◽  
Tropical Ocean ◽  
Ozone Levels

Abstract. We present the chemistry-climate model UM_CAM in which a relatively detailed tropospheric chemical module has been incorporated into the UK Met Office's Unified Model version 4.5. We obtain good agreements between the modelled ozone/nitrogen species and a range of observations including surface ozone measurements, ozone sonde data, and some aircraft campaigns. Four 2100 calculations assess model responses to projected changes of anthropogenic emissions (SRES A2), climate change (due to doubling CO2), and idealised climate change associated changes in biogenic emissions (i.e. 50% increase of isoprene emission and doubling emissions of soil-NOx). The global tropospheric ozone burden increases significantly for all the 2100 A2 simulations, with the largest response caused by the increase of anthropogenic emissions. Climate change has diverse impacts on O3 and its budgets through changes in circulation and meteorological variables. Increased water vapour causes a substantial ozone reduction especially in the tropical lower troposphere (>10 ppbv reduction over the tropical ocean). On the other hand, an enhanced stratosphere-troposphere exchange of ozone, which increases by 80% due to doubling CO2, contributes to ozone increases in the extratropical free troposphere which subsequently propagate to the surface. Projected higher temperatures favour ozone chemical production and PAN decomposition which lead to high surface ozone levels in certain regions. Enhanced convection transports ozone precursors more rapidly out of the boundary layer resulting in an increase of ozone production in the free troposphere. Lightning-produced NOx increases by about 22% in the doubled CO2 climate and contributes to ozone production. The response to the increase of isoprene emissions shows that the change of ozone is largely determined by background NOx levels: high NOx environment increases ozone production; isoprene emitting regions with low NOx levels see local ozone decreases, and increase of ozone levels in the remote region due to the influence of PAN chemistry. The calculated ozone changes in response to a 50% increase of isoprene emissions are in the range of between –8 ppbv to 6 ppbv. Doubling soil-NOx emissions will increase tropospheric ozone considerably, with up to 5 ppbv in source regions.

scholarly journals Photochemical environment over Southeast Asia primed for hazardous ozone levels with influx of nitrogen oxides from seasonal biomass burning

2021 ◽  
Vol 21 (3) ◽  
pp. 1917-1935
Author(s):  
Margaret R. Marvin ◽  
Paul I. Palmer ◽  
Barry G. Latter ◽  
Richard Siddans ◽  
Brian J. Kerridge ◽  
...  
Keyword(s):  
Nitrogen Oxides ◽  
Southeast Asia ◽  
Biomass Burning ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Transport Model ◽  
Dry Season ◽  
Ozone Exposure ◽  
Ozone Production ◽  
Ozone Levels

Abstract. Mainland and maritime Southeast Asia is home to more than 655 million people, representing nearly 10 % of the global population. The dry season in this region is typically associated with intense biomass burning activity, which leads to a significant increase in surface air pollutants that are harmful to human health, including ozone (O3). Latitude-based differences in the dry season and land use distinguish two regional biomass burning regimes: (1) burning on the peninsular mainland peaking in March and (2) burning across Indonesia peaking in September. The type and amount of material burned in each regime impact the emissions of nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs), which combine to produce ozone. Here, we use the nested GEOS-Chem atmospheric chemistry transport model (horizontal resolution of 0.25∘ × 0.3125∘), in combination with satellite observations from the Ozone Monitoring Instrument (OMI) and ground-based observations from Malaysia, to investigate ozone photochemistry over Southeast Asia in 2014. Seasonal cycles of tropospheric ozone columns from OMI and GEOS-Chem peak with biomass burning emissions. Compared to OMI, the model has a mean annual bias of −11 % but tends to overestimate tropospheric ozone near areas of seasonal fire activity. We find that outside these burning areas, the underlying photochemical environment is generally NOx-limited and dominated by anthropogenic NOx and biogenic non-methane VOC emissions. Pyrogenic emissions of NOx play a key role in photochemistry, shifting towards more VOC-limited ozone production and contributing about 30 % of the regional ozone formation potential during both biomass burning seasons. Using the GEOS-Chem model, we find that biomass burning activity coincides with widespread ozone exposure at levels that exceed world public health guidelines, resulting in about 260 premature deaths across Southeast Asia in March 2014 and another 160 deaths in September. Despite a positive model bias, hazardous ozone levels are confirmed by surface observations during both burning seasons.

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