The onset of the South China Sea summer monsoon (SCSSM) profoundly impacts meteorological conditions over East Asia. However, whether the interannual variability in monsoon onset date impacts ozone (O₃) pollution remains unclear. Here, we investigate the relationship between the early onset of SCSSM and late spring O₃ in southern China. Our results show notable differences in surface O₃ concentrations before and after SCSSM onset during early onset events in southern China. The enhanced O₃ of 11.1 µg m^-3 is supported by increased air temperature and solar radiation of 1.1 K and 30.9 W m^-2 and reduced relative humidity of -5.7%. Both observation and model simulations confirm that O₃-favorable meteorological conditions modulated by early SCSSM onset can be found in May. It increases the boundary layer height and biogenic emissions of volatile organic compounds, enhancing O₃ by 10 µg m^-3 over southern China. Chemical processes dominate such increases in O₃ with enhanced chemical production of 0.27 Tg month^-1. Descending motion in southern China vertically transports O₃ to the surface by 0.10 Tg month^-1, whereas horizontal advection reduces O₃ concentration by 0.12 Tg month^-1. The meteorological responses to colder sea surface temperature (SST) in the central equatorial Pacific are pronounced, leading to higher O₃ concentrations over the Yangtze River Delta, while warmer SST in the Philippine Sea contributes O₃ over the Pearl River Delta and eastern China. This study highlights the importance of SCSSM onset with respect to O₃ in southern China, with promising applications in management of air pollution and agriculture.

How to cite: Zhang, X., Lu, X., Wang, F., Zhou, W., Wang, P., and Gao, M.: Enhanced late spring ozone in southern China by early onset of the South China Sea summer monsoon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2868, https://doi.org/10.5194/egusphere-egu24-2868, 2024.

Ozone (O₃) deposition contributes 20% to the annual global tropospheric O₃ loss, affecting surface air quality,, the ecosystem and climate change. Limited by the instrument and method shortage, O₃ deposition in China, experiencing significantly increasing O₃ exposure, was less observed and investigated. Here, we conducted a comprehensive measurement of O₃ deposition over the wheat canopy at a typical polluted agricultural site of North China Plain using a new relaxed eddy accumulation (REA-O₃ flux) system. O₃ deposition flux and velocity (V_d) were at the averages of -0.25±0.39 μg m^-2 s^-1 and 0.29±0.33 cm s^-1, respectively. Daytime V_d (0.40±0.38 cm s^-1) was obviously higher than in the nighttime (0.17±0.26 cm s^-1). V_d played a decisive effect on the diel pattern of deposition flux, while O₃ concentration determined the flux variability on the longer timescales. The temporal changes of V_d were mainly determined by crop growth during wheat growing season, with predominantly contribution of stomatal uptake. Both daytime and nighttime V_d exhibited significant increase with decreasing relative humidity, and increasing friction velocity and soil water content, enhanced by higher leaf area index. With rapid increase of soil moisture, simultaneous and following overall increments in V_d were detected, attributed that stomatal conductance increased and opening extended to the night, remarkably strengthening O₃ stomatal uptake, and soil NO emission might be strengthened at moist condition, facilitating non-stomatal O₃ removals at night. The study suggests the leading effects of crop growth on O₃ deposition modulated by environmental condition and the non-negligible influences of nocturnal plant activities, and emphasizes the needs for O₃ deposition observation over different surface and accurate evaluation of O₃ agricultural impacts based on deposition fluxes.

How to cite: Zhang, X., Xu, W., Lin, W., Zhang, G., Geng, J., Zhou, L., Zhao, H., Zhou, G., and Xu, X.: Ozone deposition measurements over wheat fields in the North China Plain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6893, https://doi.org/10.5194/egusphere-egu24-6893, 2024.

Climate change and air pollution are two intimately interlinked global concerns. The frequency, intensity and duration of heatwaves are projected to increase globally under future climate change. A growing body of evidence indicates that health risks associated with the joint exposure to heatwaves and air pollution can be greater than that due to individual factors. However, the co-occurrences of heat and air pollution extremes in China remain less explored in the observational records. Here we investigate the spatial pattern and temporal trend of frequency, intensity, and duration of co-occurrences of heat and air pollution extremes using China’s nationwide observations of hourly PM_2.5 and O₃, and the ERA5 reanalysis dataset over 2013–2020. We identify a significant increase in the frequency of co-occurrence of wet-bulb temperature (T_w) and O₃ exceedances (beyond a certain predefined threshold), mainly in the Beijing-Tianjin-Hebei (BTH) region (up by 4.7 days decade^-1) and the Yangtze River Delta (YRD). In addition, we find that the increasing rate (compared to the average levels during the study period) of joint exceedance is larger than the rate of T_w and O₃ itself. For example, T_w and O₃ co-extremes increased by 7.0% in BTH, higher than the percentage increase of each at 0.9% and 5.5%, respectively. We identify same amplification for YRD. This ongoing upward trend in the joint occurrence of heat and O₃ extremes should be recognized as an emerging environmental issue in China, given the potentially larger compounding impact to public health.

How to cite: Xiao, X., Xu, Y., Zhang, X., Wang, F., Lu, X., Cai, Z., Brasseur, G., and Gao, M.: Amplified upward trend of the joint occurrences of heat and ozone extremes in China over 2013–2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2869, https://doi.org/10.5194/egusphere-egu24-2869, 2024.

Daily thresholds of meteorological factors relative to severe summer ozone pollution are determined in the North China Plain (NCP), the Fenhe River and Weihe River Plain (FWP), the Sichuan Basin (SCB), the Changjiang River Plain (CJR) and Pearl River Delta (PRD) by combing ozone concentrations at air quality monitoring stations and meteorological elements at weather stations. These regions share same daily thresholds, namely maximum temperature above 30 °C, relative humidity below 80%, rainfall below 10 mm and radiation in the scope of 17~27 MJ/m² together with wind speed in the range of 0.5~3.0 m/s. The adverse meteorological frequency combining daily thresholds of wind speed and radiation shows individual trend and periodic characteristics in each region after conducting 10-year moving average, namely rising with 3~6 percentage points/decade in NCP (in June), FWP (in June, July and August) and CJR (in July) while decreasing with 2~3 percentage points in SCB in July and August. However, there are no apparent trends in PRD. Additionally, these frequencies are periodic with 8.3 years to 25 years. The frequencies are positively related to Western Pacific Subtropical High (WPSH) in NCP, FWP, CJR and PRD, while negatively relevant in SCB. The correlate coefficients between Southern Oscillation and the frequencies vary in regions and months. With cyclo-stationary empirical orthogonal function analysis, we also substantiate impacts of global warming, Pacific Decadal Oscillation, El-Nino and La-Nina on WPSH in two typical months. These would give us more insights on meteorological effects on ozone pollution and be helpful for its projection.

How to cite: Li, Y., Gao, Q., Gao, W., Du, W., and Rehfeld, K.: Thresholds of Meteorological Factors Conductive to Severe Summer Ozone Pollution in China and Relation of Occurrence Frequency with Large Scale Circulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15699, https://doi.org/10.5194/egusphere-egu24-15699, 2024.

Heatwaves are phenomena that are occurring with increasing frequency, a trend which is expected to continue over the coming century as the effects of climate change continue to be felt, as has been well documented in the IPCC’s AR6 synthesis report. Heatwaves are of direct concern to human health due to exposure to extreme heat, but also for their secondary impacts including those on air pollution. 

A heatwave describes a period of hot weather where the air temperature exceeds a climatological average for that region, for example the UK’s Met Office defines these based on the average temperature in a region for the 15th July 1991 - 2020. The meteorology surrounding heatwaves is usually characterised by stagnant conditions, allowing air pollutants to remain closer to their sources and allowing secondary pollutants to form there. Tropospheric ozone is one of these air pollutants, created through the reactions of nitrogen oxides and volatile organic compounds and is harmful to human health.

As a part of the World Meteorological Organisation’s Air Quality and Climate Bulletin (2023), we included a short report on the effects of the July 2022 heatwave on ozone concentrations measured across several hundred air quality monitoring stations which were located primarily in urban and rural background locations in Europe. Here we present an extended analysis examining heatwave events over the last decade and their contribution to the number of extreme ozone events experienced at these sites.

How to cite: Drysdale, W., Nelson, B., Wilson, S., and Lee, J.: Effects of Heatwaves on European Ground Level Ozone Pollution in Recent Years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9865, https://doi.org/10.5194/egusphere-egu24-9865, 2024.

The World Health Organization (WHO) estimates that air pollution is responsible for more than seven million premature deaths every year around the world. Above background concentrations, tropospheric ozone (O₃) exerts negative effects on human health and vegetation. High ozone production occurs in conditions of strong sunlight and high temperature, as the acceleration of ozone formation is associated with high temperatures and photolysis. Therefore, it is a secondary pollutant that results from the reaction between nitrogen oxides (NOx) and volatile organic compounds (VOCs) released into the atmosphere from natural or anthropogenic activities. The combination of sunlight with non-methane hydrocarbons (NMHCs) and NOx (NO + NO2) from biomass burning can also contribute to an increase in tropospheric ozoneconcentration values. The main objective of this research is to study the tropospheric ozoneconcentration through the analysis of some precursors, between 2004 and 2022, over Portugal's mainland. In the present analysis, several predictors were selected, such as Surface Solar Radiation Downwards (SSRD), Fire Radiative Power (FRP), Temperature, Nitrogen Dioxide (NO₂), and Time of the Year (TOY). The FRP data used has been delivered in near real-time, since 2004, by the EUMETSAT Land Surface Analysis Satellite Applications Facility (LSA-SAF). The SSRD, ozone concentration and the remaining variables were collected from the Copernicus Atmosphere Monitoring Service (CAMS) reanalysis. The SSRD data is obtained from the ERA5 database, while the other variables are from the EAC4 database. A stepwise regression was applied to selected predictors used to evaluate the influence of each on ozone concentration and two models to estimate mean and maximum ozone tropospheric concentration were proposed. To understand the synoptic atmospheric patterns linked to tropospheric ozone concentration, spatial patterns of geopotential 850 mb, sea mean level pressure, vertical velocity, air temperature, and wind speed were analyzed during days characterized by high and low ozone concentrations. The regression models proposed have been tested using the Monte Carlo procedure and both models show high accuracy and robustness. Results also show a relevant contribution of FRP to mean and maximum ozone concentrations, namely for the composite of days characterized by high ozone concentration. In the present context of climate change and considering the foreseen increase of fire activity and severity, the proposed models revealed to be a useful tool for estimating tropospheric ozone concentration during the recent extreme fire events and also for analyzing the potential impacts of those concentrations on health and ecosystems. 

Acknowledgements:

This study is partially supported by the European Union’s Horizon 2020 research project FirEUrisk (Grant Agreement no. 101003890), by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020- IDL,  DHEFEUS - 2022.09185.PTDC and by European Investment Funds by FEDER/COMPETE/POCI– Operacional Competitiveness and Internacionalization Programme, under Project POCI-01-0145-FEDER-006958 and National Funds by FCT - Portuguese Foundation for Science and Technology, under the project UID/AGR/04033/2020.

How to cite: Alonso, C., A. Santos, J., and Gouveia, C.: Analysis of tropospheric ozone predictors and their relationship with the occurrence of fires in mainland Portugal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10961, https://doi.org/10.5194/egusphere-egu24-10961, 2024.

The vertical representativeness of ambient air pollutant concentration measurements is addressed rarely though it is a very important aspect influencing the use and correct interpretation of measured values. Presently not much information on the vertical distribution of ambient ozone (O₃) from sites representing relatively unpolluted rural areas is available. We explored the daily mean O₃ concentrations measured at four heights above the ground (2, 8, 50 and 230 m) at the rural Central European site Košetice in 2015–2021. We aimed to explore in detail the O₃ behaviour above the measuring point in close vicinity of the ground. We used the semiparametric GAM (generalised additive model) approach (with complexity or roughness-penalised splines implementation) to analyse the data with sufficient flexibility. Our models for both O₃ concentration and O₃ gradients used (additive) decomposition into annual trend and seasonality. Our results indicated consistently increasing O₃ with increasing height above the ground. The vertical O₃ concentration gradient in 2–230 m is not uniform, however, but changes substantially with increasing height and shows by far the highest dynamics near the ground between 2 and 8 m, differing in both the seasonal and annual aspects for all the air columns inspected. Study of O₃ concentrations at one site at several different heights above the ground brings useful results complementing ground-based ambient air quality monitoring, provides a deeper insight into the 3D structure of the atmosphere and the pollution, and provides valuable information for environmental studies exploring processes above the ground (Hůnová et al., 2023).  Knowledge on vertical distribution of O₃ concentrations near ground is for example an important input to ecological and environmental studies associating the air pollution with its impact on birds flying tens or hundred meters above the ground or impacts on tree canopies localised some tens of meters above the ground (Reif et al., 2023).

References:

Hůnová I., Brabec M., Malý M., 2023. Ambient ozone at a rural Central European site and its vertical concentration gradient close to the ground. Environmental Science and Pollution Research 30, 80014–80028. https://doi.org/10.1007/s11356-023-28016-8.

Reif J., Gamero A., Flousek J., Hůnová I., 2023. Ambient ozone – new threat to birds in mountain ecosystems? Science of the Total Environment 876, 162711. doi: 10.1016/j.scitotenv.2023.162711.

Acknowledgements:

Ozone concentration measurements at the tall tower used for the analysis were financially supported by the project ACTRIS-CZ LM2018122 and ACTRIS-CZ RI (CZ.02.1.01/0.0/0.0/16_013/0001315). This study was partially supported from the long-term strategic development financing of the Institute of Computer Science (Czech Republic RVO 67985807) and by the Czech Hydrometeorological Institute research project ʽDlouhodobá koncepce rozvoje výzkumné organizace (DKRVO) Český hydrometeorologický ústav’ financed by the Czech Ministry of the Environment.

How to cite: Hůnová, I., Brabec, M., and Malý, M.: Vertical concentration gradient of ambient ozone – insight into seven-year continuous measurements at a rural Central European site tall tower, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2874, https://doi.org/10.5194/egusphere-egu24-2874, 2024.

Volatile organic compounds (VOCs) are, together with nitrogen oxides (NO_x), important precursor substances from which ground-level ozone (O₃) can be formed through complex reaction chains. As there are only low regulatory requirements for VOC measurements in the EU, VOCs are only sparsely recorded in the air quality monitoring networks in Germany and Europe, in contrast to ozone and nitrogen oxides. However, in order to determine trends, check the effectiveness of emission reduction strategies and the correctness of emission inventories, be able to allocate emission sources and better understand ozone formation and the spread of its precursors, it is necessary to carry out long-term measurements of ozone precursors with a higher temporal resolution.

To check their suitability for continuous time-resolved VOC monitoring especially in measurement networks, two commercially available online-GC systems were tested over a time-period of about 1 1/2 years at a station of the air quality monitoring network in Saxony, Germany. Comparing the raw concentrations obtained from these two automated systems, the parameters of the regression are ranging from a slope of 0.4 and an R² of 0.13 for ethene to a slope of 2 and a R² of 0.54 for toluene. Both instruments required a significant maintenance effort and due to a number of hardware and software issues, a data availability of 73-76 % was achieved. The biggest issue with the raw data quality arose from retention time shifts, especially for low boiling point compounds, leading to frequent misclassifications of chromatographic peaks. Time-consuming manual or semi-manual reprocessing of the raw data is mandatory to increase the data quality to a more acceptable level. With the reprocessed data, a slope of 1.6 and R² of 0.59 for ethene and a slope of 1.3 and R² of 0.85 for propane as best-case example can be reached.

Approximately 20 of the 61 calibrated compounds could be measured on a regular basis including BTX aromatics and small chain alkanes and alkenes. Concentrations are ranging from 0.03 ppb for most of the aromatics and longer chain alkanes and alkenes up to 2.2 ppb for C₂ and C₃ compounds. During the vegetation period, biogenic VOCs and especially isoprene show higher concentrations of up to 7.6 ppb. From the measured seasonal trends and diurnal and weekly patterns, influences from different emission sources such as local traffic, heating or vegetation can be obtained and first results will be presented. In addition, together with the respective photochemical ozone creation potential (POCP) values of the measured VOCs, the influence of regional precursor emissions on the ozone concentration can be determined.

How to cite: Hell, M., van Pinxteren, D., Bastian, S., and Herrmann, H.: Comparison of time-resolved continuous measurements of ozone precursor VOCs in Borna, Saxony (Germany) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17957, https://doi.org/10.5194/egusphere-egu24-17957, 2024.

Tropospheric ozone (O₃) is a major concern in the atmosphere due to its adverse effects on human health and vegetation. O₃ is a secondary pollutant, formed through complex photochemical processes from its precursors like nitrogen oxides (NO_X) such as volatile organic compounds (VOCs). The Mediterranean coastline is particularly sensitive to human activities, under a climate with high insolation, under a climate with high solar radiation where a large part of the year prevails a regime of mesoscale winds (breezes) supported by a favourable orography. Large metropolitan areas, such as the city of Valencia, contribute to photochemistry with important emissions of NO_X and VOCs to the atmosphere, especially traffic, which determines high levels of ozone in the surrounding areas. However, there are other sources that can also play a relevant role in atmospheric photochemistry, which are not well known and do not have a sufficiently detailed emission profile speciation. This study deals with the analysis of the VOCs associated with three types of common emission sources (gas stations, ports and car painting shops) in a Mediterranean city, in this case Valencia. This could lead to a significant improvement in the urban VOC speciation for emission inventories used in model simulations, especially for O₃ in future studies.

10 passive samplers for VOCs were installed for two weeks during summertime when O₃ levels are typically elevated (from 29 June to 13 July 2023). Four samplers were placed at two gas stations (two each), three in areas influenced by the Port of Valencia, and the remaining three in nearby three different car painting shops. The measured VOC levels were analysed through gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). Additionally, for more precise temporal resolution, proton-transfer-reaction mass spectrometry (PTR-MS) was installed at a gas station in another Mediterranean city (Castellon) during July 2023.

As a result, the total VOC concentrations are generally high in car painting shops with an average of 52.4 µg m^-3, followed by gas stations (44.0 µg m^-3 as an average) and ports (26.4 µg m^-3). Looking at the contribution of the functional groups, aldehydes are clearly the largest contributors for gas stations and ports (28.5% and 34.3%, respectively), while for car painting shops, the contribution of this group is comparable to aromatics (24.4% and 26.1%, respectively). Analysing the species, formaldehyde (aldehydes) is generally one of the main contributors for the three environments, accounting for 6.7%, 8.5%, and 5.3% of the total VOCs for gas stations, ports and car painting shops, respectively. 2-methylpentane (alkane) (5.3%) and acetone (ketone) (5.1%) are the second most important species for gas stations and ports, respectively, and the third one is acetaldehyde for both environments (4.6% and 4.9%, respectively). Meanwhile, butyl acetate (ester) and methylcyclohexane (aromatic) have also high levels for car painting shops (8.3% and 7.1%, respectively). These species, with the exception of acetone, have significant ozone formation potential, which could lead to elevated O₃ levels in the western vicinity of the city.

How to cite: Jung, D., Mantilla, E., Borrás, E., Vera, T., and Muñoz, A.: Characterization of VOC sources in a typical urban environment (Valencia), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18035, https://doi.org/10.5194/egusphere-egu24-18035, 2024.

Tropospheric Ozone (O₃) is a secondary pollutant known for its positive radiative forcing and detrimental effects on air quality, human health, and ecosystems. In plants, O₃ acts as a strong oxidant, affecting cellular and molecular processes, e.g. modifying rubisco activity, reducing stomatal conductance, and inducing early leaf senescence. This study aims to evaluate the effects of O₃ on Gross Primary Production (GPP) at six forest sites: five European sites (Belgium, France, Finland and Italy) and one tropical site in the Congo Basin. We employed a modelling approach, contrasting simulations of GPP with and without the influence of O₃ using the Joint UK Land Environment Simulator (JULES), a land surface model used to study soil-vegetation-atmosphere interactions. The JULES model was calibrated for each site, adjusting key parameters, using historical climate data and soil properties to align with each location's specific environmental and vegetation characteristics. Therefore, we forced the model using measurements of local tropospheric O₃, CO₂, and meteorological variables. We conducted two simulations for each site: one representing the existing O₃ levels observed at each site and another under O₃-free conditions. This comparative approach enabled us to isolate the specific effects of O₃ on GPP to quantify this effect. Our findings reveal a difference in the sensitivity of the contrasting forest ecosystems to O₃ exposure. The correlation values between modelled GPP with O₃ and observed GPP vary between 0.786 in Castelporziano, Italy and 0.933 in Hyytiälä, Finland. Consequently, the European sites, encompassing a range of climatic and ecological conditions, displayed diverse responses to O₃, and the GPP reduction varies along the different sites. The GPP reduction due to O₃ exposure varied across sites, ranging from -1.52% in Hyytiälä, Finland, to -9.79% in Castelporziano, Italy. This study shows the necessity of long-term monitoring datasets combined with process-based models to understand better the O₃ impacts at several ecosystems.

How to cite: Vieira, I., Meunier, F., Sitch, S., Brown, F., Duran Rojas, C., Gerosa, G., Jansseans, I., Boeckx, P., Bauters, M., and Verbeeck, H.: Assessing the effects of surface ozone on forest GPP: a vegetation model approach using JULES, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11946, https://doi.org/10.5194/egusphere-egu24-11946, 2024.

This study compares tropospheric ozone (O₃) concentrations measured at Union Glacier (UG), Antarctica, in December 2023 with long-term trends and observations reported in recent literature. Ground-measurements for continuous gas and particulate matter monitoring were carried out at UG (West Antarctica), nearby the Estación Polar Conjunta Glaciar Unión (79° 46´S 82° 19´W). Union Glacier, which with ~2561 km², is one of the largest outlet glaciers in the Ellsworth Mountains, flowing to the Ronne-Filchner Ice Shelf. Ozone concentrations were measured using an ETL-ONE multiparametric air quality monitoring station equipped with an UniTec SENS-IT O₃ metal oxide sensor, which shows strong correlation with the Federal Reference Methods (FRMs) for O₃, for both field (R² ~ 0.72-0.83) and laboratory studies (R² >0.80 ). During over one week of monitoring with 1-minute resolution, we observed high O₃ levels at UG (mean: 45.8 ppb), significantly exceeding typical polar values. These findings are juxtaposed with analyses from various studies spanning over two decades, offering a broader context of O₃ dynamics in polar regions.

Kumar et al. (2021) and Helmig et al. (2007) documented increasing surface O₃ trends in Antarctica, associating them with climate issues and radiative processes. Our observations at UG align with these increasing trends but notably surpass the projected mean values, suggesting additional local or transient factors influencing O₃ levels. As observed in our study, the possible intrusion of stratospheric O₃ resonates with Yan Xia et al. (2023) findings, emphasizing the impact of stratospheric-tropospheric exchange, particularly during sudden stratospheric warming events.

Furthermore, the subtle yet persistent O₃ increases noted by Law et al. (2023) in the Arctic provide a comparative baseline, highlighting the polar-specific atmospheric dynamics. Our data also contribute to understanding the complex interplay of O₃ with nitrogen oxides (NOx), as discussed by Zhou et al. (2020), indicating that background NOx might play a crucial role in O₃ variability.

In light of these comparative analyses, our study underscores the importance of continued and enhanced O₃ monitoring in Antarctica to decipher the underlying mechanisms driving its distribution. These findings are particularly crucial for predicting future climate impacts and understanding the role of polar regions in global atmospheric chemistry. They advocate for a more nuanced understanding of polar O₃ trends, factoring in localized events and broader climatic influences to elucidate the evolving narrative of tropospheric O₃ in these remote regions.

Acknowledgment to INACH Project RT_34-21 and ANID Proyect: Anillo ACONCAGUA ACT210021, Fondecyt Regular 1221526 and FOVI230167.

References:

Helmig et al. (2007)

Kumar et al. (2021)

Law et al. (2023)

Yan Xia et al. (2023)

Zhou et al. (2020)

How to cite: Díaz Robles, L. A., Vallejo Gallardo, F., Campos Bravo, V., Fadic, X., Barcaza, G., Moosmuller, H., and Cereceda-Balic, F.: Comparative analysis of tropospheric ozone concentrations at Union Glacier, Antarctica: long-term observations and recent measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13666, https://doi.org/10.5194/egusphere-egu24-13666, 2024.

High emissions of NO_x and anthropogenic VOCs from urban areas are a major source of tropospheric ozone production. Tropospheric ozone is a secondary air pollutant that is harmful to human health as well as crop and ecosystem productivity, and an important greenhouse gas. It is formed from the chemical processing of NO_x and VOCs in a non-linear cycle, making ozone reduction strategies challenging. Urban centres across the world are developing at different rates and emitting different combinations and concentrations of chemical species, resulting in location specific drivers of urban ozone concentrations. Alongside this, different countries and cities have implemented a wide range of location specific air quality and climate change measures to reduce air pollution and greenhouse gas emissions. The diversity of these policies over the past few decades has further led to different outcomes for secondary pollutant formation across the globe.

As part of TOAR-II, long-term trends in urban ozone concentrations over the past 20 years across over 400 sites in Europe and the USA will be explored. This study utilises the TOAR database, accessed via the TOAR Data Portal, which collects hourly data of long-term surface air quality measurements from over 10,000 stations globally. Using ground-based data from air quality monitoring networks, seasonal trends in ozone and NO₂ concentrations are explored alongside trends in peak ozone and MDA8.  Global 5-year trends in ozone and NO₂ will also be examined, extending the analysis to include urban centres in China and South America. The period between 2018-2022 will be investigated, allowing us to take a closer look into the impact of COVID-19 in cities across the world. This study aims to assess trends in urban ozone and NO₂ across Europe and the USA, and to explore how lockdowns and restrictions during the COVID-19 pandemic might reveal insights into a lower NO_x emission future.

How to cite: Nelson, B., Drysdale, W., and Lee, J.: Long-term trends in urban ozone in Europe and the USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9759, https://doi.org/10.5194/egusphere-egu24-9759, 2024.

From May 20 through July 25, 2023, large boreal forest fire plumes were transported across the central and eastern United States of America. On many days the U.S. Environmental Protection Agency (EPA) air quality monitoring network detected co-located ozone and PM2.5 anomalies, which indicate a contribution from the smoke to surface ozone production. We apply a general additive mixed model (GAMM) to interpolate the observed ozone and PM2.5 observations onto daily maps of the continental United States.  Comparison to a recent baseline period with below-average wildfire activity (2014, 2016, 2019) allows for the identification of smoke events that contributed to enhanced surface ozone levels.

How to cite: Cooper, O., Chang, K.-L., and McDonald, B.: Co-occurrence of boreal smoke plumes and enhanced surface ozone across the central USA during summer 2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3240, https://doi.org/10.5194/egusphere-egu24-3240, 2024.

Biomass burning emits large quantities of ozone precursors, nitrogen oxides (NO_x) and volatile organic compounds (VOCs), to the lower atmosphere.  Recent analysis of ozone and tracers for biomass burning and urban emissions in the remote atmosphere shows that a larger fraction of tropospheric ozone may be attributable to biomass burning than global models predict.  At continental and regional scales, increasing trends in biomass burning emissions in North America are associated with enhanced ozone in U.S. cities.  Ozone production within smoke plumes leads to enhanced regional scale backgrounds, while interaction of aged smoke with urban NO_x pollution may lead to increased rates of ozone production depending on the local NO_x sensitivity regime.  Several recent airborne and ground-based field studies have investigated ozone in biomass burning influenced air.  The 2016-2018 Atmospheric Tomography Mission (ATom) sampled remote tropospheric biomass burning influence. The 2019 Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) sampled wildfire smoke across the U.S. with multiple research aircraft.  The 2022 California Fire Dynamics Experiment (CalFiDE) conducted focused in-situ and remote sensing measurements in California and Oregon.  Ground-based measurements in Boulder, Colorado intercepted periods of smoke influence in the Northern Front Range urban area in 2020 and 2021.  Finally, the 2023 Atmospheric Emissions and Reactivity Observed from Megacities to Marine Areas (AEROMMA) campaign on the NASA DC-8 and the Coastal Urban Plume Dynamics Study (CUPiDS) on the NOAA Twin Otter observed long range smoke transported to U.S. urban areas and the associated impacts on ozone.  These studies provide a comprehensive analysis of the biomass burning influence on tropospheric ozone at all scales, from near field plume chemistry to the global remote troposphere, and from the continental background to local urban influence.

How to cite: Brown, S., Bourgeios, I., Chace, W., Coggon, M., Langford, A., Peischl, J., Rickly, P., Robinson, M., Senff, C., and Zuraski, K.: Biomass burning influence on tropospheric ozone from recent airborne and ground-based field studies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20824, https://doi.org/10.5194/egusphere-egu24-20824, 2024.

Land cover has significant impacts on local meteorology and biogenic volatile organic compounds (BVOCs) emissions, which in turn affects surface ozone air quality. The Guangdong-Hong Kong-Macau Greater Bay Area (GBA) is a hotspot of ozone air pollution, where BVOCs play an important role. The importance of BVOCs in ozone air pollution strengthens during heatwaves, and heatwaves have been increasing in frequency and intensity in the past two decades. Therefore, it is critical to have accurate BVOCs emissions in atmospheric chemistry models for simulating ozone air quality and supporting the design of efficient ozone air pollution control strategies. However, current BVOCs emissions derived from the outdated and coarse (0.25° x 0.3125° spatial resolution) Community Land Model version 4.5 (CLM4) plant functional types (PFT) map based on Moderate Resolution Imaging Spectroradiometer (MODIS) land cover dataset in 2000 is far from sufficient for producing an accurate BVOCs emission inventory in the GBA. What is more, the CLM4 BVOCs emissions do not consider the substantial land cover change in the GBA in the past two decades, thus incapable of simulating ozone responses to land cover change on a decadal timescale. In this study, we employ the 30m Finer Resolution Observation and Monitoring of Global Land Cover (FROM_GLC2017) map for simulating meteorology with the WRF model and deriving an updated BVOCs emission inventory with MEGAN for September 2017, during which time a one-week heatwave event happened in the GBA. The online two-way coupled regional meteorology-chemistry model WRF-GC v2.0 with the detailed Greater Bay Area anthropogenic emission inventory (GBA-EI) reproduces the MDA8 ozone during non-heatwaves (r = 0.71, NMB = 4.21%), but has significant low biases for MDA8 ozone during heatwaves (r = 0.26, NMB = 27.32%). We find that updating the land cover data from U.S. Geological Survey (USGS) and CLM4 to FROM_GLC2017 is promising to correct the biased low ozone during heatwaves. Compared with the original USGS land cover map, broadleaf evergreen tree forest cover, which has a high BVOCs yield and responds swiftly to temperature increase, increases by 37.29%. Concurrently, the cropland cover, which has a relatively low BVOCs yield, decreases by 44.62%. We will go on to investigate how land cover changes affect ozone trends in the GBA in the past two decades with the long-term FROM_GLC2017 land cover dataset.

How to cite: Zhang, J., Zhai, S., and Tai, A. P. K.: Responses of biogenic volatile organic compound emissions and surface ozone air pollution in the Greater Bay Area to heatwaves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15216, https://doi.org/10.5194/egusphere-egu24-15216, 2024.

This work analyzes ground-level ozone trends in South America, an understudied region with scarce comprehensive trend estimates. We present an updated regional analysis and test a hypothesis proposing that the recent increase in ozone levels, particularly in urban environments, may be linked to intense wildfires induced by extreme meteorological events within a preexisting volatile organic compounds (VOC)-limited regime. Utilizing the quantile regression method, we estimate trends, quantify uncertainties, and identify change points. Short- and long-term exposure is assessed using the maximum daily 8-hour average and peak season metrics. Our findings reveal lower ozone levels in tropical cities (Bogotá and Quito), ranging between 39-43 ppbv for short-term and 26-27 for long-term exposure. In contrast, extratropical cities (Santiago and São Paulo) exhibit higher ozone levels, with short-term exposure at 61 ppbv and long-term exposures between 40-41 ppbv. Santiago (since 2017) and São Paulo (since 2008) show positive trends of 0.6 ppbv yr^-1 and 0.2 ppbv yr^-1, respectively, with very high certainty. We attribute these upward trends, or the absence of evidence of variation as observed in Bogotá and Quito, to the established VOC-limited regime. However, the higher increase in extreme percentile trends (≥ 90th) is linked to the impact of wildfires and biomass burning, particularly in southwestern South America, associated with extreme meteorological configurations.

How to cite: Seguel, R., Castillo, L., Opazo, C., Rojas, N., Nogueira, T., Cazorla, M., Gavidia-Calderón, M., Gallardo, L., Garreaud, R., Carrasco, T., and Elshorbany, Y.: Surface Ozone Trends in South America: Unraveling the Influence of Precursor Shifts and Extreme Events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11737, https://doi.org/10.5194/egusphere-egu24-11737, 2024.

Tropospheric ozone is generated by photochemical reactions by precursor pollutants, or it can also proceed from stratospheric intrusion. In addition to affecting the population's health, ozone exposure threatens biodiversity conservation and the production of food and forest products.

A prior study by this research group assessed public ozone monitoring stations across Chile, revealing that only stations near the Andes Mountains in central Chile exceed the national standard of 61 ppb. The highest concentrations were observed at Las Condes station (790 m.a.s.l.) and Los Andes station (830 m.a.s.l.).

In this context, the present study aimed to determine whether tropospheric ozone exists in high concentrations in the Andes Mountains range at higher altitudes and its behavior. For this reason, an ozone monitoring station was installed at the NUNATAK-1 refuge laboratory, located in Portillo (32.844ºS, 70.129ºW), east of the Los Andes station, at 3,000 m.a.s.l. The monitoring period for this study spanned from October 6, 2022, to October 18, 2023, with minute resolution using Thermo Scientific™ 49iQ Ozone Monitor, which employs a dual cell UV photometry (sample and reference) to measure the amount of ozone in the air from ppb levels up to 200 ppm, (detection limit: 0.50 ppb in 60 second averaging time; precision: ±1.0 ppb; response time: 20 seconds).

During the monitoring period, hourly averages of up to 80 ppb were observed, and the 99th percentile of the maximum daily 8-hour moving average was 61.56 ppb, exceeding the Chilean standard. The Portillo records were compared with Chile's most contaminated monitoring stations, Las Condes and Los Andes, using an ANOVA test, and a p-value ≤ 0.05 was obtained. Therefore, it is concluded that there are statistically significant differences between the stations. The LSD test further determined that Portillo exhibited a significantly higher average ozone concentration, with levels averaging 55% higher than those in Los Andes and 58% higher than those in Las Condes.

In the northern hemisphere, elevated tropospheric ozone levels have been observed in high-altitude regions, including the western US, western Europe, central Japan, central China, Himalayas, Greenland, southern Algeria, and Izaña. However, in the southern hemisphere, ozone in mountainous areas has not been studied as extensively due to poor data coverage. This study unveils ozone records spanning a year in the Andes Mountains, revealing even higher concentrations than those observed in urban areas in Chile. Therefore, tropospheric ozone could be harming the biodiversity of the Andes Mountain range in central Chile. Furthermore, ozone could adversely affect the health of climbers and hikers exploring the Andes Mountain range.

Subsequent studies should determine whether the tropospheric ozone recorded in the Andes Mountains range results from long-distance ozone or precursor pollutants transport from urban source regions, or ozone intrusion from the stratosphere. Photochemical modeling is recommended for a more comprehensive understanding and monitoring campaigns of the vertical ozone profile using radiosonde.

Acknowledgment to ANID Project: Anillo ACONCAGUA ACT210021, Fondecyt Regular 1221526, FOVI230167, and ANID National PhD Scholarship 21202033.

How to cite: Campos, V., Díaz-Robles, L., Fadic, X., Ruggeri, M. F., Vallejo, F., Barcaza, G., Fu, J. S., and Cereceda-Balic, F.: High levels and behavior of tropospheric ozone in the Andes Mountains, Central Chile, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13411, https://doi.org/10.5194/egusphere-egu24-13411, 2024.

A tropospheric ozone Climate Data Record from 1995 until end 2023 has been generated within ESA’s Climate Change Initiative programme. The GOME-type Tropical Tropospheric Ozone Essential Climate Variable (GTTO-ECV) satellite data record combines data from GOME, SCIAMACHY, OMI, the three GOME-2 missions and TROPOMI. The retrieval is based on the Convective Cloud Differential technique, which limits the coverage to the tropical belt (20°S to 20°N). We generated two monthly mean data sets at 1° x 1° resolution: one corresponds to a tropospheric column up to 200 hPa as in the previous CCI data release (Heue et al., 2016), while the other is limited to 270 hPa this pressure level is used in the operational S5P data set. Besides a consistent reprocessing of the CCD data for individual sensors, we also updated the harmonising scheme. The mean bias as well as the mean annual cycle relative to the reference instrument (OMI) are used to correct for the differences between the sensors.

Heue et al (2016) inferred a mean tropospheric ozone trend of +0.7±0.1 DU/decade (1995-2015) from the previous GTTO-ECV version. Did the trend change with the extended and improved data set? The GTTO-ECV data record will be used to investigate the tropical mean trend as well as temporal and local changes in the trends or extreme events.

How to cite: Heue, K.-P., Loyola, D., Coldewey-Egbers, M., van Gent, J., van Roozendael, M., and Hubert, D.: The GOME-type Tropical Tropospheric Ozone Essential Climate Variable (GTTO-ECV) satellite data record between 1995 and 2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5050, https://doi.org/10.5194/egusphere-egu24-5050, 2024.

The transport sector (i.e. aviation, land-based transport and shipping) is an important source of emissions of ozone precursors such as nitrogen oxides (NO_x), volatile organic compounds (VOCs) and carbon monoxide (CO). The formation of ozone from these precursors is a highly non-linear process which depends strongly on atmospheric background conditions (i.e., emissions from other sectors and meteorological conditions) and on the amount of transport emissions. As the different transport sectors emit at different geographical locations under different background conditions, their impact on tropospheric ozone cannot be estimated simply by comparing the emission shares. Instead, model-based spatially resolving approaches are needed that include a detailed ozone source attribution. To do this, we quantified for the first time the contribution of each transport sector to tropospheric ozone in a consistent way using the EMAC global chemistry-climate model equipped with an ozone source apportionment technique (called TAGGING). We performed simulations for present-day (2015) and for 2050 under the Shared Socioeconomic Pathways (SSP) SSP1-1.9, SSP2-4.5 and SSP3-7.0 and analysed the contributions of land-based transport from different geographical regions, shipping, and aviation to ozone. Based on these calculated contributions, we quantify the ozone radiative forcing (RF) attributable to emissions from the transport sector.

For 2015, we estimate an ozone RF attributable to emissions from land-based transport, shipping and aviation of 121 mWm^-2, 60 mWm^-2, and 31 mWm^-2,respectively. Compared to 2015, only SSP1-1.9 shows a strong decrease of ozone RF attributable to the entire transport sector in 2050. For the SSP2-4.5 scenario, we find similar RFs of the entire transport sector as for 2015, while the RFs in SSP3-7.0 increase compared to 2015.

How to cite: Mertens, M., Brinkop, S., Grewe, V., Hendricks, J., Jöckel, P., Lanteri, A., Matthes, S., and Righi, M.: The contribution of transport emissions to ozone mixing ratios in 2015 and 2050 in the Shared Socioeconomic Pathways (SSPs), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10612, https://doi.org/10.5194/egusphere-egu24-10612, 2024.

We present an analysis of ozone data products retrieved from multiple satellite observations. Specifically, we highlight data from the TRopospheric Ozone and its Precursors from Earth System Sounding (TROPESS) project which is a NASA effort that provides retrievals of atmospheric ozone utilizing radiances from a variety of different satellite instruments. The multispectral retrievals of ozone utilize the Multi-Spectra, Multi-Species, Multi-Sensors Retrievals of Trace Gases (MUSES) retrieval framework to produce consistent estimations of ozone from different satellite radiances. TROPESS ozone data products are retrieved from the Atmospheric Infrared Sounder (AIRS), the Ozone Monitoring Instrument (OMI), the Cross-track Infrared Sounder (CrIS) instruments, and combinations of these satellites.

Trends in ozone are presented and evaluated using records dating from 2002 to the present. Trends are investigated globally and regionally, and validated against ozonesonde measurements. We find that the magnitude of ozone vertical profiles and columns agree between satellites to a high degree, but we are still investigating the trends seen in the different data sets. We investigate the causes of these differences between satellites, including instrument type and vertical sensitivity of the retrievals. We show ongoing work investigating comparisons between the TROPESS ozone data products, chemical reanalysis products using the MOMO-Chem framework, other satellite products, and ground-based observations, as well as trends in ozone precursors.

How to cite: Pennington, E., Neu, J., Bowman, K., Miyazaki, K., and Osterman, G.: Quantification and evaluation of TROPESS ozone trends, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13520, https://doi.org/10.5194/egusphere-egu24-13520, 2024.

Surface ozone is a major air pollutant that harms not only human health but also crop and vegetation productivity. The continuously rising atmospheric CO₂concentration can affect surface ozone levels through various vegetation-mediated ecophysiological pathways. These pathways include higher leaf densityfollowing CO₂ fertilization, which can lead to increased biogenic volatile organic compound (BVOC) emissions and dry deposition, inhibition of BVOC emissions due to competitive biochemical effects in leaves, and lower stomatal conductance resulting in lower dry deposition. In this study, we implemented an ecophysiology module that explicitly links the computation of dry deposition velocity and isoprene emission to photosynthesis calculation in the GEOS-Chem global 3-D chemical transport model, and conducted model experiments to simulate the effects of rising CO₂ levels on surface ozone pollution via CO₂ fertilization, isoprene inhibition and stomatal closure under an atmospheric CO₂ level projected by Representative Concentration Pathway (RCP) 8.5 scenarios in 2050, with 2010 as the base year for comparison. The effects of rising CO₂ on enhancement in leaf area index (LAI) were simulated separately using a land surface model (Community Land Model, CLM). The simulated results indicate that the CO₂-induced ecophysiological effects depend largely on the environmental regime and plant traits. The combination of all the CO₂-induced ecophysiological responses lead to –3 to +5 ppbv of changes in surface ozone. While for the simulated results with the ecophysiology module implemented, the effects of all ecophysiological pathways result in an overall decrease in ozone levels by –0.047% in global tropospheric ozone burden, which corresponds to –2 to +2 ppbv of changes in surface ozone. In regions with low-NO_x environment and dense vegetation, the effect of CO₂ fertilization outweighs that of isoprene inhibition and stomatal closure, giving an overall decrease in ozone. In high-NO_x environment like North America and Europe, the effect of isoprene inhibition offsets that of CO₂ fertilization or stomatal closure. By comparing with the results, the impact of rising CO₂ on ozone levels is found to beoverall modest due to the counteracting effects of different pathways, but can be regionally important for specific pathways, underscoring the necessity of comprehensively analysing the interplay between the atmosphere and biosphere when examining the influence of increasing CO₂ on global atmospheric chemistry. 

How to cite: Cheng, K. W. K., Tai, A. P. K., and Wong, A. Y. H.: Effects of Rising CO2 Concentration on Global Ozone Air Quality , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14247, https://doi.org/10.5194/egusphere-egu24-14247, 2024.

Tropospheric ozone (O₃) is an important short-lived climate forcer and a critical secondary air pollutant, detrimental to human health and ecosystems. It is the dominant source of the hydroxyl radical OH that is highly reactive with organic and inorganic compounds. Global tropospheric O₃ concentrations have been rising considerably since the pre-industrial period as a result of the increase in the anthropogenic emissions of O₃ precursors. Assessing the long-term tropospheric O₃ trends is critical for understanding the impact of human activity and climate change on atmospheric chemistry.

Since 2007, the IASI (Infrared Atmospheric Sounding Interferometer) instruments have been embarked on board the polar-orbiting meteorological satellites Metop-A, -B and -C. The European Organization for the Exploitation of Meteorological Satellites (EUTMETSAT) is currently reprocessing the IASI O₃ dataset providing a homogeneous record of O₃.

In this study, we aim to assess tropospheric ozone distributions and trends on the global and regional scales for the period 2008-2023 using the homogeneous IASI O₃ dataset. Comparisons of the IASI data with the Cross-track Infrared Sounder (CrIS) satellite observations are also performed.

How to cite: Boynard, A., Wespes, C., Hadji-Lazaro, J., Hurtmans, D., Coheur, P.-F., Doutriaux Boucher, M., Bowman, K., and Clerbaux, C.: Tropospheric ozone global and regional distributions and trends from IASI, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19159, https://doi.org/10.5194/egusphere-egu24-19159, 2024.