Distribution Of O3 Research Articles

Sources and Trends of CO, O3, and Aerosols at the Mount Bachelor Observatory (2004–2022)

Understanding baseline O3 is important as it defines the fraction of O3 coming from global sources and not subject to local control. We report the occurrence and sources of high baseline ozone days, defined as a day where the daily maximum 8 h average (MDA8) exceeds 70 ppb, as observed at the Mount Bachelor Observatory (MBO, 2.8 km asl) in Central Oregon from 2004 to 2022. We used various indicators and enhancement ratios to categorize each high-O3 day: carbon monoxide (CO), aerosol scattering, the water vapor mixing ratio (WV), the aerosol scattering-to-CO ratio, backward trajectories, and the NOAA Hazard Mapping System Fire and Smoke maps. Using these, we identified four causes of high-O3 days at the MBO: Upper Troposphere/Lower Stratosphere intrusions (UTLS), Asian long-range transport (ALRT), a mixed UTLS/ALRT category, and events enhanced by wildfire emissions. Wildfire sources were further divided into two categories: smoke transported in the boundary layer to the MBO and smoke transported in the free troposphere from more distant fires. Over the 19-year period, 167 high-ozone days were identified, with an increasing fraction due to contributions from wildfire emissions and a decreasing fraction of ALRT events. We further evaluated trends in the O3 and CO data distributions by season. For O3, we found an overall increase in the mean and median values of 2.2 and 1.5 ppb, respectively, from the earliest part of the record (2004–2013) compared to the later part (2014–2022), but no significant linear trends in any season. For CO, we found a significant positive trend in the summer 95th percentiles, associated with increasing fires in the Western U.S., and a strong negative trend in the springtime values at all percentiles (1.6% yr−1 for 50th percentile). This decline was likely associated with decreasing emissions from East Asia. Overall, our findings are consistent with the positive trend in wildfires in the Western United States and the efforts in Asia to decrease emissions. This work demonstrates the changing influence of these two source categories on global background O3 and CO.

The potential of drone observations to improve air quality predictions by 4D-Var

Abstract. Vertical profiles of atmospheric pollutants, acquired by uncrewed aerial vehicles (UAVs, known as drones), represent a new type of observation that can help to fill the existing observation gap in the planetary boundary layer (PBL). This article presents the first study of assimilating air pollutant observations from drones to evaluate the impact on local air quality analysis. The study uses the high-resolution air quality model EURAD-IM (EURopean Air pollution Dispersion – Inverse Model), including the four-dimensional variational data assimilation system (4D-Var), to perform the assimilation of ozone (O3) and nitrogen oxide (NO) vertical profiles. 4D-Var is an inverse modelling technique that allows for simultaneous adjustments of initial values and emissions rates. The drone data were collected during the MesSBAR (automated airborne measurement of air pollution levels in the near-earth atmosphere in urban areas) field campaign, which was conducted in Wesseling, Germany, on 22–23 September 2021. The results show that the 4D-Var assimilation of high-resolution drone measurements has a beneficial impact on the representation of regional air pollutants within the model. On both days, a significant improvement in the vertical distribution of O3 and NO is noticed in the analysis compared to the reference simulation without data assimilation. Moreover, the validation of the analysis against independent observations shows an overall improvement in the bias, root mean square error, and correlation for O3, NO, and NO2 (nitrogen dioxide) ground concentrations at the measurement site as well as in the surrounding region. Furthermore, the assimilation allows for the deduction of emission correction factors in the area near the measurement site, which significantly contributes to the improvement in the analysis.

Asymmetries in the Simulated Ozone Distribution on TRAPPIST-1e due to Orography

TRAPPIST-1e is a tidally locked rocky exoplanet orbiting the habitable zone of an M dwarf star. Upcoming observations are expected to reveal new rocky exoplanets and their atmospheres around M dwarf stars. To interpret these future observations we need to model the atmospheres of such exoplanets. We configured Community Earth System Model version 2–Whole Atmosphere Community Climate Model version 6, a chemistry climate model, for the orbit and stellar irradiance of TRAPPIST-1e assuming an initial Earth-like atmospheric composition. Our aim is to characterize the possible ozone (O3) distribution and explore how this is influenced by the atmospheric circulation shaped by orography, using the Helmholtz wind decomposition and meridional mass streamfunction. The model included Earth-like orography, and the substellar point was located over the Pacific Ocean. For such a scenario, our analysis reveals a north–south asymmetry in the simulated O3 distribution. The O3 concentration is highest at pressures >10 hPa (below ∼30 km) near the south pole. This asymmetry arises from the higher landmass fraction in the northern hemisphere, which causes drag in near-surface flows and leads to an asymmetric meridional overturning circulation. Catalytic species were roughly symmetrically distributed and were not found to be primary driver for the O3 asymmetry. The total O3 column density was higher for TRAPPIST-1e compared to Earth, with 8000 Dobson units (DUs) near the south pole and 2000 DU near the north pole. The results emphasize the sensitivity of O3 to model parameters, illustrating how incorporating Earth-like orography can affect atmospheric dynamics and O3 distribution. This link between surface features and atmospheric dynamics underlines the importance of how changing model parameters used to study exoplanet atmospheres can influence the interpretation of observations.

Consistency evaluation of tropospheric ozone from ozonesonde and IAGOS (In-service Aircraft for a Global Observing System) observations: vertical distribution, ozonesonde types, and station–airport distance

Abstract. The vertical distribution of tropospheric O3 from ozonesondes is compared with that from In-service Aircraft for a Global Observing System (IAGOS) measurements collected at 23 pairs of sites between about 30° S and 55° N from 1995 to 2021. Profiles of tropospheric O3 from IAGOS are generally in good agreement with ozonesonde observations from electrochemical concentration cells (ECCs), Brewer–Mast sondes, and carbon–iodine sensors, with average biases of 2.58, −0.28, and 0.67 ppb and correlation coefficients (R) of 0.72, 0.82, and 0.66, respectively. Agreement between aircraft and Indian-sonde observations is poor, with an average bias of 15.32 ppb and an R value of 0.44. The O3 concentration observed by ECC sondes is, on average, 5 %–10 % higher than that observed by IAGOS, and the relative bias increases modestly with altitude. For other sonde types, there are some seasonal and altitudinal variations in the relative bias with respect to the IAGOS measurements, but these appear to be caused by local differences. The distance between the station and airport, when within 4° (latitude and longitude), has little effect on the comparison results. For the ECC ozonesondes, the overall bias with respect to the IAGOS measurements varies from 5.7 to 9.8 ppb when the station pairs are grouped by station–airport distances of <1° (latitude and longitude), 1–2°, and 2–4°. Correlations for these groups correspond to R=0.8, 0.9, and 0.7. These comparison results provide important information for merging ozonesonde and IAGOS measurement datasets. They can also be used to evaluate the relative biases of different sonde types in the troposphere, using the aircraft as a transfer standard.

Predicting plateau atmospheric ozone concentrations by a machine learning approach: A case study of a typical city on the southwestern plateau of China

Atmospheric ozone (O3) has been placed on the priority control pollutant list in China's 14th Five-Year Plan. Due to their unique meteorological conditions, plateau regions contain high concentrations of atmospheric O3. However, traditional experimental methods for determining O3 concentrations using automatic monitoring stations cannot predict O3 trends. In this study, two machine learning models (a nonlinear auto-regressive model with external inputs (NARX) and a temporal convolution network (TCN)) were developed to predict O3 concentrations in a plateau area in the Kunming region by considering the effects of meteorological parameters, air quality parameters, and volatile organic compounds (VOCs). The plateau O3 prediction accuracy of the machine learning models was found to be much higher than those of numerical models that served as a comparison. The O3 values predicted by the machine learning models closely matched the actual monitoring data. The temporal distribution of plateau O3 displayed a high all-day peak from February to May. A correlation analysis between O3 concentrations and feature parameters demonstrated that humidity is the feature with the highest absolute correlation (−0.72), and was negatively correlated with O3 concentrations during all test periods. VOCs and temperatures were also found to have high positive correlation coefficients with O3 during periods of significant O3 pollution. After negating the effects of meteorological parameters, the predicted O3 concentrations decreased significantly, whereas they increased in the absence of NOx. Although individual VOCs were found to greatly affect the O3 concentration, the total VOC (TVOC) concentration had a relatively small effect. The proposed machine learning model was demonstrated to predict plateau O3 concentrations and distinguish how different features affect O3 variations.

Disentangling the effects of meteorology and emissions from anthropogenic and biogenic sources on the increased surface ozone in Eastern China

China's Clean Air Actions have substantially improved ambient PM2.5 air quality since 2013. However, ozone (O3) pollution in urban areas has worsened in recent years, particularly in the eastern region. The formation of O3 in these high emission areas is highly complex and regulated by numerous factors. Utilizing the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), this study conducted a comprehensive analysis through nine sensitivity experiments for the years 2013 and 2017, aimed at disentangling the relative contributions of major factors (e.g., meteorological factors, anthropogenic emissions, biogenic emissions, and aerosol feedback mechanisms) to the observed O3 concentration trends in Jiangsu, a developed region of China with increasing trend of O3 level. Our findings indicate a pronounced increase in mean daily maximum 8-h average (MDA8) O3 levels in the economically vibrant southern Jiangsu, contrasted with a decrease in the less developed northern regions. The study identifies anthropogenic emissions change as the primary driver of O3 variations, with significant impacts also attributed to meteorological conditions and aerosol feedback effects, while biogenic emission shifts play a lesser role. In terms of meteorological factors, we discovered that the alteration in meteorological thermal factors (enhanced solar radiation and temperatures) in 2017, compared to 2013, exerted a more pronounced influence on the formation of O3 than the change in thermally driven dynamic factors (boundary layer height and wind speed). Moreover, the study observes a shift in O3 formation sensitivity from VOC-sensitive to transitional or NOX-sensitive regimes, signifying a notable transformation in the regional atmospheric chemistry conducive to O3 generation. Aerosol feedback effects, through complex pathways including photolysis rate alterations and modifications in the vertical O3 distribution, further compound the challenge of mitigating O3 levels. Our research underscores the necessity for adaptive, region-specific strategies to mitigate O3 pollution, providing potential insights for policymakers to formulate effective control measures.

Multi-instrumental analysis of ozone vertical profiles and total columns in South America: comparison between subtropical and equatorial latitudes

Abstract. The behavior of ozone gas (O3) in the atmosphere varies according to the region of the globe. Its formation occurs mainly in the tropical stratosphere through the photodissociation of molecular oxygen with the aid of the incidence of ultraviolet solar radiation. Still, the highest concentrations of O3 content are found in high-latitude regions (poles) due to the Brewer–Dobson circulation, a large-scale circulation that takes place from the tropics to the pole in the winter hemisphere. This work presents a multi-instrumental analysis at two Brazilian sites, a subtropical one (Santa Maria – 29.72° S, 53.41° W) and an equatorial one (Natal – 5.4° S, 35.4° W), to investigate ozone distributions in terms of vertical profiles (2002–2020) and total abundance in terms of total columns of ozone (1979–2020). The study is based on the use of ground-based and satellite observations. Ozone profiles over Natal, from the ground up to the mesosphere, are obtained by radiosonde experiments (0–30 km) in the framework of the SHADOZ program and by satellite measurements from the SABER instrument (15–60 km). This enabled the construction of a continuous time series for ozone, including monthly values and climatological trends. There is a good agreement between the two measurements in the common observation layer, mainly for altitudes above 20 km. Below 20 km, SABER ozone profiles showed high variability and overestimated ozone mixing ratios by over 50 %. Dynamic and photochemical effects can interfere with O3 formation and distribution along higher latitudes through the Brewer–Dobson circulation. The measurements of the total ozone columns used are in good agreement with each other (TOMS/OMI × Dobson for Natal and TOMS/OMI × Brewer for Santa Maria) in time and space, in line with previous studies for these latitudes. Wavelet analysis was used over 42 years. The investigation revealed a significant annual cycle in both data series for both sites. The study highlighted that the quasi-biennial oscillation (QBO) plays a significant role in the variability of stratospheric ozone at the two study sites – Natal and Santa Maria. The QBO's contribution was found to be stronger at the Equator (Natal) than at the subtropics (Santa Maria). Additionally, the study showed that the 11-year solar cycle also has a significant impact on ozone variability at both locations. Given the study latitudes, the ozone variations observed at the two sites showed different patterns and amounts. Only a limited number of studies have been conducted on stratospheric ozone in South America, particularly in the region between the Equator and the subtropics. The primary aim of this work is to investigate the behavior of stratospheric ozone at various altitudes and latitudes using ground-based and satellite measurements in terms of vertical profiles and total columns of ozone.

The dynamics and transport of ozone in the gas and liquid phase generated by air surface microdischarge plasma at atmospheric pressure

AbstractThis contribution focuses on the spatial‐temporal behavior and reactive pathways of O3 produced by a surface air microdischarge in the gas and liquid phase using ultraviolet absorption spectroscopy. The findings demonstrate that mode transition from ozone to nitrogen oxide over time is observed at a constant input power higher than ~0.60 W/cm2. Due to the long‐lived characteristic and ionic wind, the perpendicular distribution of O3 is almost uniform. The maximum penetration depth is around 5 mm, and the gas–liquid mass transfer efficiency is approximately 0.4‱ at a depth of 1 mm, when the treatment time is 10 min. The mass transfer of O3 between gas and liquid phases is dominated by the liquid convention induced by ionic wind.

Vertical distribution of ozone in spring based on two high tower observations over the Pearl River Delta, China

This study investigates the vertical distribution characteristics of ozone (O3) in the Pearl River Delta (PRD) region during spring, utilising observational data from two tall towers in urban and suburban areas of the PRD, i.e., the 600 m high Canton Tower and the 356 m high Shenzhen Meteorology Gradient Tower (SZMGT), between 2018 and 2020. The observations indicate that the peak times of O3 concentrations differ under polluted and clean conditions, with polluted conditions showing 1–3 h later peaks compared with clean conditions. The diurnal variation in the O3 concentration is more pronounced at the SZMGT than at the Canton Tower. The O3 vertical gradients differ between the two towers, with the Canton Tower showing larger daytime gradients and the SZMGT showing larger nighttime gradients under polluted conditions. The vertical O3 distribution patterns are categorised into three types: Polluted, Moderate, and Good levels. The O3 concentration initially rises with altitude and then decreases under polluted conditions. Elevated O3 is observed in the lower planetary boundary layer (PBL), approximately between 110 and 210 m in height, where the concentration is 1.1–1.4 times higher than the surface level. Both the Moderate and Good levels occur under clean conditions, in which the O3 of the Canton Tower increases with altitude, whereas the O3 of the SZMGT first increases and then decreases with altitude. The correlation between O3 and the meteorological conditions (temperature, relative humidity, wind direction, and wind speed) decreases with increasing altitude. The cluster analysis of backward trajectories identifies three main transport paths affecting the O3 levels: northeasterly continental, southerly oceanic, and easterly coastal paths. Combining the observations from O3 lidar in Guangzhou and Shenzhen and two additional cities within the PRD region, Foshan and Zhongshan, the analysis of a typical pollution case indicates that different cities have different local chemical generation and regional transport contributions to O3 pollution. A conceptual model reflecting the horizontal transport paths and vertical structures of O3 pollution in the spring over the PRD is proposed, which enhances our understanding of the O3 vertical distribution in different cities and contributes to the analysis of the O3 pollution mechanism in the PRD agglomeration.

A Comprehensive Review of Surface Ozone Variations in Several Indian Hotspots

Ozone at ground level (O3) is an air pollutant that is formed from primary precursor gases like nitrogen oxides (NOx) and volatile organic compounds (VOCs). It plays a significant role as a precursor to highly reactive hydroxyl (OH) radicals, which ultimately influence the lifespan of various gases in the atmosphere. The elevated surface O3 levels resulting from anthropogenic activities have detrimental effects on both human health and agricultural productivity. This paper provides a comprehensive analysis of the variations in surface O3 levels across various regions in the Indian subcontinent, focusing on both spatial and temporal changes. The study is based on an in-depth review of literature spanning the last thirty years in India. Based on the findings of the latest study, the spatial distribution of surface O3 indicates a rise of approximately 50–70 ppbv during the summer and pre-monsoon periods in the northern region and Indo-Gangetic Plain. Moreover, elevated levels of surface O3 (40–70 ppbv) are observed during the pre-monsoon/summer season in the western, southern, and peninsular Indian regions. The investigation also underscores the ground-based observations of diurnal and seasonal alterations in surface O3 levels at two separate sites (rural and urban) in Kannur district, located in southern India, over a duration of nine years starting from January 2016. The O3 concentration exhibits an increasing trend of 7.91% (rural site) and 5.41% (urban site), ascribed to the rise in vehicular and industrial operations. This review also presents a succinct summary of O3 fluctuations during solar eclipses and nocturnal firework displays in the subcontinent.

Characterization of Spatial and Temporal Variations in Air Pollutants and Identification of Health Risks in Xi’an, a Heavily Polluted City in China

The study of the temporal and spatial characteristics of air pollutants in heavily polluted cities is extremely important for analyzing the causes of pollution and achieving a viable means of control. Such characteristics in the case of Xi’an, a typical heavily polluted city in Fenwei Plain, China, have remained unclear due to limitations in data accuracy and research methods. The monthly, daily, and hourly patterns of O3 and particulate matter (PM2.5 and PM10) are analyzed in this study using on-site data provided by an urban air quality monitoring network. The analysis of variance (ANOVA) method was used to compare differences in pollutant concentrations during different seasons and time periods. The spatial distributions of O3, PM2.5, and PM10 at different time points following interpolation of the air quality monitoring sites have been analyzed. The results show that the O3 concentration from 12 p.m. to 3 p.m. was significantly higher than that in the morning and evening, and the concentrations of PM2.5 and PM10 from 7 p.m. to 10 p.m. were significantly higher than those in the morning and afternoon. The number of qualified days for PM2.5 was less than 30 and unqualified days for O3 was more than 100 in 2019. There is a potential risk of exposure to pollution with associated health risks. Even on the same day, the spatial pollutant distributions at different time points can differ significantly. This study provides a scientific basis for reducing O3 and particulate matter exposure. Outdoor activities in the morning in summer are more beneficial to reduce O3 exposure, and outdoor activities should be curtailed in the evening in winter to reduce particulate exposure. This study provides a scientific basis for the government to formulate public health policies to reduce pollution exposure from outdoor activities.

Exploring the spatial effects and influencing mechanism of ozone concentration in the Yangtze River Delta urban agglomerations of China.

Ground-level ozone (O3) pollution has emerged as a significant concern impacting air quality in urban agglomerations, primarily driven by meteorological conditions and social-economic factors. However, previous studies have neglected to comprehensively reveal the spatial distribution and driving mechanism of O3 pollution. Based on the O3 monitoring data of 41 cities in the Yangtze River Delta (YRD) from 2014 to 2021, a comprehensive analysis framework of spatial analysis-spatial econometric regression was constructed to reveal the driving mechanism of O3 pollution. The results revealed the following: (1) O3 concentrations in the YRD exhibited a general increasing and then decreasing trend, indicating an improvement in pollution levels. The areas with higher O3 concentration are mainly the cities concentrated in central and southern Jiangsu, Shanghai, and northern Zhejiang. (2) The change of O3 concentration and distribution is the result of various factors. The effect of urbanization on O3 concentrations followed an inverted U-shaped curve, which implies that achieving higher quality urbanization is essential for effectively controlling urban O3 pollution. Traffic conditions and energy consumption have significant direct positive influences on O3 concentrations and spatial spillover effects. The indirect pollution contribution, considering economic weight, accounted for about 35%. Thus, addressing overall regional energy consumption and implementing traffic source regulations are crucial paths for O3 pollution control in the YRD. (3) Meteorological conditions play a certain role in regulating the O3 concentration. Higher wind speed will promote the diffusion of O3 and increase the O3 concentration in the surrounding city. These findings provide valuable insights for designing effective policies to improve air quality and mitigate ozone pollution in urban agglomeration area.

Changes of PM2.5 and O3 and their impact on human health in the Guangdong-Hong Kong-Macao Greater Bay Area.

In recent years, the combined pollution of PM2.5 and O3 in China, particularly in economically developed regions such as the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), has garnered significant attention due to its potential implications. This study systematically investigated the changes of PM2.5 and O3 and their associated human health effects in the GBA, utilizing observational data spanning from 2015 to 2019. The findings revealed a spatial trend indicating a gradual decrease in PM2.5 levels from the northwest to the southeast, while the spatial distribution of MDA8 O3 demonstrated an opposing pattern to that of PM2.5. The monthly fluctuations of PM2.5 and MDA8 O3 exhibited V-shaped and M-shaped patterns, respectively. Higher MDA8 O3 concentrations were observed in autumn, followed by summer and spring. Over the five-year period, PM2.5 concentrations exhibited a general decline, with an annual reduction rate of 1.7μgm-3/year, while MDA8 O3 concentrations displayed an annual increase of 3.2μgm-3. Among the GBA regions, Macao, Foshan, Guangzhou, and Jiangmen demonstrated notable decreases in PM2.5, whereas Jiangmen, Zhongshan, and Guangzhou experienced substantial increases in MDA8 O3 levels. Long-term exposure to PM2.5 in 2019 was associated with 21,113 (95% CI 4968-31,048) all-cause deaths (AD), 1333 (95% CI 762-1714) cardiovascular deaths (CD), and 1424 (95% CI 0-2848) respiratory deaths (RD), respectively, reflecting declines of 27.6%, 28.0%, and 28.4%, respectively, compared to 2015. Conversely, in 2019, estimated AD, CD, and RD attributable to O3 were 16,286 (95% CI 8143-32,572), 7321 (95% CI 2440-14,155), and 6314 (95% CI 0-13,576), respectively, representing increases of 45.9%, 46.2%, and 44.2% over 2015, respectively. Taken together, these findings underscored a shifting focus in air pollution control in the GBA, emphasizing the imperative for coordinated control strategies targeting both PM2.5 and O3.

Mixing-layer-height-referenced ozone vertical distribution in the lower troposphere of Chinese megacities: stratification, classification, and meteorological and photochemical mechanisms

Abstract. Traditional tropospheric ozone (O3) climatology uses a simple average substantially smoothed stratification structure in individual O3 profiles, limiting our ability to properly describe and understand how O3 is vertically distributed at the interface between the mixing layer (ML) and free troposphere (FT). In this study, we collected 1897 ozonesonde profiles from two Chinese megacities (Beijing and Hong Kong) over the period 2000–2022 to investigate the climatological vertical heterogeneity of the lower-tropospheric O3 distribution with a mixing-layer-height-referenced (h-referenced) vertical coordinate system. The mixing-layer height (h) was first estimated following an integral method that integrates the information of temperature, humidity, and cloud. After that, a so-called h-referenced vertical distribution of O3 was determined by averaging all individual profiles expressed as a function of z/h rather than z (where z is altitude). We found that the vertical stratification of O3 is distributed heterogeneously in the lower troposphere, with stronger vertical gradients at the surface layer and ML–FT interface. There are low vertical autocorrelations of O3 between the ML and FT but high autocorrelations within each of the two atmospheric compartments. These results suggest that the ML–FT interface acts as a geophysical “barrier” separating air masses of distinct O3 loadings. This barrier effect varies with season and city, with an ML–FT detrainment barrier in summer (autumn) and an FT–ML entrainment barrier in other seasons in Beijing (Hong Kong). Based on a Student's t test, daily h-referenced O3 profiles were further classified into three typical patterns: MLO3-dominated, FTO3-dominated, and uniform distribution. Although the FTO3-dominated pattern occurs most frequently during the whole study period (69 % and 54 % of days in Beijing and Hong Kong, respectively), the MLO3-dominated pattern prevails in the photochemically active season, accounting for 47 % of summer days in Beijing and 54 % of autumn days in Hong Kong. These occurrences of the MLO3-dominated pattern are significantly more frequent than in previously reported results at northern mid-latitudes, indicating intensive photochemical MLO3 production under the high-emission background of a Chinese megacity. From a FTO3-dominated to MLO3-dominated pattern, the O3 precursor CH2O (NO2) experiences a substantial increase (decrease) in Beijing but a slight change in Hong Kong. Vertically, the increment of CH2O is larger in the upper ML, and the decrement of NO2 is larger in the lower ML. Such vertical changes in O3 precursors push O3 production sensitivity away from the VOC-limited regime and facilitate high-efficiency production of O3 via photochemical reactions, particularly in the upper ML of Beijing.

Geometric anisotropic Semi-variogram analysis of ozone levels in Daerah Istimewa Yogyakarta, Indonesia

Identification of areas with high O3 levels that pose a risk to public health is necessary. Ordinary co-kriging is a geostatistical method that determines the value of primary variables at specific locations using weighted values of secondary parameters. A Semi-variogram is required to demonstrate the spatial correlation between the observations measured using this method. This study aims to determine the best Semi-variogram model and produce a map of the predicted O3 level interpolation results using the ordinary co-kriging method with a geometric anisotropic Semi-variogram. Data from the first quarter of 2018’s air quality monitoring in Daerah Istimewa Yogyakarta (DIY) were used to interpolate O3 levels, with 72 points for CO levels and 53 points for O3 levels. The results showed that the Semi-variogram model with the lowest mean error (ME) value is a gaussian model that differs from the spherical model by only 0.003. The Gaussian model has the lowest root mean squared error (RMSE), but it is only 0.002 different from the spherical model. However, by comparing the mean squared deviation ratio (MSDR) values of the three models, the spherical model’s MSDR value is the lowest. A comprehensive analysis showed that the spherical geometric anisotropic Semi-variogram model performed superior, resulting in the smallest minimum mean error (ME), root mean square error (RMSE) and minimum squared deviation ratio (MSDR) values. These findings highlight the potential of this approach to accurately map the spatial distribution of O3 and support evidence-based decision-making related to public health.

Influence of Wind Flows on Surface O3 Variation over a Coastal Province in Southeast China

Surface ozone (O3) is influenced not only by anthropogenic emissions but also by meteorological factors, with wind direction being one of the most overlooked factors. Here, we combine the observational data of both O3 and wind flow to compare the variation in surface O3 with wind direction between coastal and inland regions of Fujian, a province in the southeast coast of China with complicated topography. We further conduct a numerical simulation using a global chemical transport model, GEOS-Chem, to interpret the observational results, explore the linkages between these O3 variations and wind flows, and identify the dominant processes for the occurrence of high O3 that varies with wind flows. The results from the observations over 2015–2021 suggest that, over coastal regions, surface O3 concentrations show a strong dependence on wind flow changes. On average, during the daytime, when southeasterly winds prevail, the mean of O3 concentrations reaches 83.5 μg/m3, which is 5.0 μg/m3 higher than its baseline values (the mean O3 concentrations), while the northwesterly winds tend to reduce surface O3 by 6.4 μg/m3. The positive O3 anomalies with southeasterly wind are higher in the autumn and summer than in the spring and winter. During the nighttime, the onshore northeasterly winds are associated with enhanced O3 levels, likely due to the airmass containing less NO2, alleviating the titration effects. Over inland regions, however, surface O3 variations are less sensitive to wind flow changes. The GEOS-Chem simulations show that the prevailing southeasterly and southwesterly winds lead to the positive anomaly of chemical reactions of O3 over coastal regions, suggesting enhanced photochemical production rates. Furthermore, southeasterly winds also aid in transporting more O3 from the outer regions into the coastal regions of Fujian, which jointly results in elevated surface O3 when southeasterly winds dominates. When affected by wind flows in different directions, the chemical reaction and transport in the inland regions do not exhibit significant differences regarding their impact on O3. This could be one of the reasons for the difference in O3 distribution between coastal and inland regions. This study could help to deepen our understanding of O3 pollution and aid in providing an effective warning of high-O3 episodes.

A multiscale geographically weighted regression kriging method for spatial downscaling of satellite-based ozone datasets

Accurate monitoring of ozone (O3) concentrations by remote sensing is essential for achieving pollution control and ecological protection. However, the existing O3 remote sensing data with a low spatial resolution do not facilitate fine-grained studies of small-scale urban clusters. In this study, the multiscale geographically weighted regression kriging (MGWRK) method was used to spatially downscale O3 remote sensing products (10 km × 10 km). Downscaling factors were selected from meteorological factors and vegetation, aerosol optical thickness (AOD), and air pollutant emission inventory data. Spatial heterogeneity and scale differences among the factors were considered and compared via multiple regression kriging (MLRK) and geographically weighted regression kriging (GWRK) to generate 1-km annual and seasonal O3 remote sensing products. The results showed that I) the downscaling accuracy of each model can be expressed as MGWRK > GWRK > MLRK; the local downscaling model yields data that are more consistent with the actual spatial distribution of O3 after considering the spatial heterogeneity of the influencing factors; and the downscaled annual and seasonal data exhibit satisfactory spatial texture characteristics and consistency with the original spatial distribution of O3, while the distribution boundary problem of image elements is eliminated. II) Nitrogen oxide (NOx) and volatile organic compound emissions and temperature exhibit strong positive correlations with O3, while wind speed, humidity, the normalized difference vegetation index, and AOD indicate weak positive correlations with O3. Moreover, precipitation exhibits a weak negative correlation with O3. III) The coefficient of determination (R2) of the 1-km resolution annual O3 concentration data after downscaling based on the MGWRK model reaches 0.93, while the RRMSE and MAE values are only 3% and 1.86, respectively, with a coefficient of variation of 9.55%; the downscaling accuracy of the seasonal O3 concentration data is higher in summer and winter than during the other seasons, with R2 greater than 0.85, further confirming the spatial and temporal downscaling advantages of the MGWRK model for O3 in the Chang-Zhu-Tan city cluster. This further corroborates the feasibility of the MGWRK model for spatial and temporal O3 downscaling in the Chang-Zhu-Tan urban area.

Preparation of carbon-coated Fe2 O3 @Ti3 C2 Tx composites by mussel-like modifications as high-performance anodes for lithium-ion batteries.

Fe2 O3 with high theoretical capacity (1007 mA h g-1 ) and low cost is a potential anode material for lithium-ion batteries (LIBs), but its practical application is restricted by its low electrical conductivity and large volume changes during lithiation/delithiation. To solve these problems, Fe2 O3 @Ti3 C2 Tx composites were synthesized by a mussel-like modification method, which relies on the self-polymerization of dopamine under mild conditions. During polymerization, the electronegative group (-OH) on dopamine can easily coordinate with Fe3+ ions as well as form hydrogen bonds with the -OH terminal group on the surface of Ti3 C2 Tx , which induces a uniform distribution of Fe2 O3 on the Ti3 C2 Tx surface and mitigates self-accumulation of MXene nanosheets. In addition, the polydopamine-derived carbon layer protects Ti3 C2 Tx from oxidation during the hydrothermal process, which can further improve the electrical conductivity of the composites and buffer the volume expansion and particle agglomeration of Fe2 O3 . As a result, Fe2 O3 @Ti3 C2 Tx anodes exhibit ~100 % capacity retention with almost no capacity loss at 0.5 A g-1 after 250 cycles, and a stable capacity of 430 mA h g-1 at 2 A g-1 after 500 cycles. The unique structural design of this work provides new ideas for the development of MXene-based composites in energy storage applications.

Future tropospheric ozone budget and distribution over east Asia under a net-zero scenario

Abstract. Under future net-zero emission policies, reductions in emissions of ozone (O3) precursors are expected to alter the temporal and spatial distributions of tropospheric O3. In this study, we quantify changes in the tropospheric O3 budget and in the spatiotemporal distribution of surface O3 in east Asia and the contributions of regional emissions, intercontinental transport and climate change between the present day and 2060 under a net-zero scenario using the NCAR Community Earth System Model (CESM) with online tagging of O3 and its precursors. The results reveal that the global tropospheric O3 burden is likely to decrease by more than 20 %, from 316 Tg in the present day to 247 Tg in 2060, under a net-zero scenario. The burden of stratospheric O3 in the troposphere is expected to increase from 69 to 77 Tg. The mean lifetime of tropospheric O3 is expected to increase by 2 d (∼10 %). Changes in climate under a net-zero pathway are relatively small and only lead to small increases in tropospheric O3. Over eastern China, surface O3 increases in winter due to the weakened titration of O3 by NO associated with reduced anthropogenic NO emissions and due to enhanced stratospheric input. In summer, surface O3 decreases by more than 30 ppbv, and peak concentrations shift from July to May. Local contributions from anthropogenic emissions to surface O3 over east Asia are highest in summer but drop substantially, from 30 % to 14 %, under a net-zero scenario. The contribution of biogenic NO sources is enhanced and forms the dominant contributor to future surface O3, especially in summer (∼40 %). This enhanced contribution is mainly due to the increased O3 production efficiency under lower anthropogenic precursor emissions. Over eastern China, local anthropogenic contributions decrease from 50 % to 30 %. The decreases in surface O3 are strongly beneficial and are more than sufficient to counteract the increases in surface O3 observed in China over recent years. This study thus highlights the important co-benefits of net-zero policies that target climate change in addressing surface O3 pollution over east Asia.

The development and application of a novel helicopter-based airborne platform for near-surface monitoring and sampling of atmospheric pollutants

This study presents a novel approach utilising helicopters as platforms for real-time monitoring of air pollutants and routine canister sampling to enhance our understanding of air pollution in the Greater Bay Area (GBA). By employing this method, local spatial and vertical distribution of various air pollutants (including CO, NO, NO2, O3, PM2.5 and VOCs) in Hong Kong could be obtained within hours for fast snapshots of air pollution.The investigation involved hovering ascent and descent operations above Tap Mun Island, revealing no indication of self-contamination from engine exhaust during the hovering process. The analysis of air pollutant spatial distribution in and around Hong Kong through multiple trips showed higher concentrations of O3 and PM2.5 in the northern region on days with episodic pollution, while urban areas exhibited elevated levels of NO2 and CO concentration. In contrast, Tap Mun Island as the background area demonstrated relatively low pollutant concentrations. The vertical distribution of concentrations of VOC species with high ozone formation potential revealed minor variations at sampling altitudes of 500 ft and 1000 ft over the waters around Hong Kong. The novel monitoring protocol using helicopters as platforms proves to be an effective approach for pollution episode investigations, offering valuable insights in the formation mechanisms and transport pathways of O3. The findings of the heterogenous spatial distribution of O3 and its precursors underscore the significance of ongoing monitoring efforts and policy development to combat air pollution in the dynamic GBA and similar regions worldwide.