Maximum Ozone Research Articles

Deciphering decadal urban ozone trends from historical records since 1980

Abstract Ozone pollution is a major environmental threat to human health. Timely assessment of ozone trends is crucial for informing environmental policy. Here we show that for the most recent decade (2013–2022) in the Northern Hemisphere, warm-season (April-September) mean daily 8-h average maximum (MDA8) ozone increases much faster in urban regions with top ozone levels (mainly in North China Plain, 1.2 ± 1.3 ppbv year−1) than that in other low-ozone regions (0.2 ± 0.9 ppbv year−1). These trends widen the ozone differences across urban regions, and increase extreme pollution levels and health threats from a global perspective. Comparison of historical trends in different urban regions reveals that, ozone increases in China during 2013–2022 differ in magnitude and mechanisms from historical periods in other regions since 1980. This reflects a unique chemical environment characterized by exceptionally high nitrogen oxides and aerosol concentrations, where reducing ozone precursor emissions leads to substantial ozone increase. Ozone increase in China has slowed down in 2018–2022 compared to 2013–2017, driven by ongoing emission reductions but with ozone-favorable weather conditions. Historical ozone evolution in Japan and South Korea indicates that ozone increases should be suppressed with continuous emission reduction. Increasing temperature and associated wildfires have also reversed ozone decreases in the US and Europe with anthropogenic ozone control slowing down in recent decades.

Ambient air pollution exposure is associated with liver fat and stiffness in Latino youth with a more pronounced effect in those with PNPLA3 genotype and more advanced liver disease

BackgroundExposure to ambient air pollutants has emerged as a risk for metabolic-dysfunction associated steatotic liver disease (MASLD). ObjectivesWe sought to examine associations between short-term (prior month) and long-term (prior year) ambient air pollution exposure with hepatic fat fraction (HFF) and liver stiffness in Latino youth with obesity. A secondary aim was to investigate effect modification by patatin-like phospholipase domain-containing protein 3 (PNPLA3) genotype and liver disease severity. MethodsData was analyzed from 113 Latino youth (age 11–19) with obesity in Southern California. Individual exposure to particulate matter with aerodynamic diameter ≤ 2.5μm (PM2.5), ≤ 10μm (PM10), nitrogen dioxide (NO2), 8-hour maximum ozone (8hrMax-O3), 24-hr O3, and redox-weighted oxidative capacity (Oxwt) were estimated using residential address histories and United States Environmental Protection Agency air quality observations. HFF and liver stiffness were measured using magnetic resonance imaging. Linear models were used to determine associations between short-term and long-term exposure to air pollutants with HFF and liver stiffness. Modification by PNPLA3 and liver disease severity was then examined. ResultsShort-term exposure to 8hrMax-O3 was positively associated with HFF. Relationships between air pollution exposure and HFF were not impacted by PNPLA3 genotype or liver disease severity. Long-term exposure to 8hrMax-O3 and Oxwt were positively associated with liver stiffness. Associations between air pollution exposure and liver stiffness depended on PNPLA3 genotype, such that individuals with GG genotypes exhibited stronger, more positive relationships between short-term exposure to PM10, 8hrMax-O3, 24-hr O3, and Oxwt and liver stiffness than individuals with CC/CG genotypes. In addition, relationships between short-term exposure to NO2 and liver stiffness were stronger in those with severe liver disease. DiscussionAir pollution exposure may be a risk factor for liver disease among Latino youth with obesity, particularly in those with other preexisting risks for liver damage.

Heatwave events and concurrent ozone concentrations between 2006 and 2022 at two sites in southern and northern Spain.

Hotter-than-usual days are becoming more common, such that heat waves are expected to increase in intensity, frequency, duration, and spatial extent in Spain. Within this framework, this paper looks at the combined effects of extreme temperatures and air pollution in two cities in Spain, Córdoba and Valladolid, over the period 2006-2022. Synoptic patterns and air mass movement were analysed during the eleven coincident heat waves at both locations in order to study what impact orography and local meteorology have on ozone concentrations. Weak flow conditions were the most frequent synoptic pattern in the Iberian Peninsula during heat waves. Moreover, west and local circulations characterised the main air trajectories at low levels (500m agl), while southwest maritime advections and African air mass transport were more frequent at higher levels (1500 and 3000m agl) in Córdoba and Valladolid, respectively. On average, maximum ozone values were higher in Córdoba (105.1µgm-3) than in Valladolid (80µgm-3) and were strongly correlated with extreme temperatures at both locations (r up to 0.8, p-value < 0.05). Mean temperature in Córdoba was 31.9°C, with the maximum value reaching 43.7°C, while temperatures in Valladolid were lower (28.3°C and 37.3°C, respectively). Calculation and assessment of some indices helped to understand the impact of extreme events. Caution actions based on the Heat Index characterised heat wave periods. Moderate risk was the general Air Quality Health Index feature recorded and reached a very high risk of unhealthy air quality in the June 2022 event in Córdoba.

Assessment of short-term effects of ambient air pollution exposure on osteoarthritis outpatient visits

The association of short-term ambient air pollution exposure with osteoarthritis (OA) outpatient visits has been unclear and no study has assessed the modifying roles of district-level characteristics in the association between ambient air pollution exposure and OA outpatient visits. We investigated the cumulative associations of ambient air pollution exposure with daily OA outpatient visits and vulnerable factors influencing the associations using data from 16 districts of Beijing, China during 2013–2019. A total of 18,351,795 OA outpatient visits were included in the analyses. An increase of 10 μg/m3 in fine particulate matter (PM2.5), inhalable particulate matter (PM10), nitrogen dioxide (NO2), sulfur dioxide (SO2), maximum 8-hour moving-average ozone (8 h-O3), and 0.1 mg/m3 in carbon monoxide (CO) at representative lag days were associated with significant increases of 0.31 %, 0.06 %, 0.77 %, 0.87 %, 0.30 %, and 0.48 % in daily OA outpatient visits, respectively. Considerable OA outpatient visits were attributable to short-term ambient air pollution exposure. In addition, low temperature and high humidity aggravated ambient air pollution associated OA outpatient visits. District-level characteristics, such as population density, green coverage rate, and urbanization rate modified the risk of OA outpatient visits associated with air pollution exposure. These findings highlight the significance of controlling ambient air pollution during the urbanization process, which is useful in policy formation and implementation.

Mesospheric Ozone Depletion during 2004–2024 as a Function of Solar Proton Events Intensity

Solar proton events (SPEs) affect the Earth’s atmosphere, causing additional ionization in the high-latitude mesosphere and stratosphere. Ionization rates from such solar proton events maximize in the stratosphere, but the formation of ozone-depleting nitrogen and hydrogen oxides begins at mesospheric altitudes. The destruction of mesospheric ozone is associated with protons with energies of about 10 MeV and higher and will strongly depend on the intensity of the flux of these particles. Most studies investigating the impact of SPEs on the characteristics of the middle atmosphere have been based on either simulations or reanalysis datasets, and some studies have used satellite observations to validate model results. We study the impact of SPEs on cold-season ozone loss in both the northern and southern hemispheres using Aura MLS mesospheric ozone measurements over the 2004 to 2024 period. Here, we show how strongly SPEs can deplete polar mesospheric ozone in different hemispheres and attempt to evaluate this dependence on the intensity of solar proton events. We found that moderate SPEs consisting of protons with an energy of more than 10 MeV and a flux intensity of more than 100 pfu destroy mesospheric ozone in the northern hemisphere up to 47% and in the southern hemisphere up to 33%. For both hemispheres, the peak of winter ozone loss was observed at about 76 km. In the northern hemisphere, maximum winter ozone loss was observed on the second day after a solar proton event, but in the southern hemisphere, winter ozone depletion was already detected on the first day. In the southern hemisphere, mesospheric ozone concentrations return to pre-event levels on the ninth day after a solar proton event, but in the northern hemisphere, even on the tenth day after a solar proton event, the mesospheric ozone layer may not be fully recovered. The strong SPEs with a proton flux intensity of more than 1000 pfu lead to a maximum winter ozone loss of up to 85% in the northern hemisphere, and in the southern hemisphere winter, ozone loss reaches 73%.

Ozone exceedance forecasting with enhanced extreme instance augmentation: A case study in Germany

Accurately forecasting ozone levels that exceed specific thresholds is pivotal for mitigating adverse effects on both the environment and public health. However, predicting such ozone exceedances remains challenging due to the infrequent occurrence of high-concentration ozone data. This research, leveraging data from 57 German monitoring stations from 1999 to 2018, introduces an Enhanced Extreme Instance Augmentation Random Forest (EEIA-RF) approach that significantly improves the prediction of days when the maximum daily 8-hour average ozone concentrations exceed 120μg/m3. A pre-trained machine learning model is used to generate additional high-concentration data, which, combined with selectively reduced low-concentration data, forms a new dataset for training a refined model. This method achieved an improvement of at least 8% in the accuracy of predicting days with ozone exceedances across Germany. Our experiment underscores the approach’s value in enhancing atmospheric modeling and supporting public health advisories and environmental policy-making related to ozone pollution.

Implications of ozone transport on air quality in the Sichuan Basin, China.

Ozone pollution is formed through complex chemical and physical processes closely associated with emissions, photochemical reactions, and meteorological conditions. The objective of this study is to quantify the contributions of meteorological chemical formation, vertical transport, and horizontal transport to air quality during spring and summer in different regions of the Sichuan Basin. The Community Multi-scale Air Quality (CMAQ) with the Integrated Process Rate (IPR) was employed to simulate the months of April and July 2021 in the Sichuan Basin. The results indicate that both the spring and summer chemical formation of ozone in the urban centre show negative values, while the surrounding urban areas contribute positively, with chemical formation ranging from 0 to 10 μg·m-3. The maximum ozone level due to horizontal transport in the urban centre exceeds 20 μg·m-3, whereas horizontal transport in the surrounding urban areas exhibits negative values, with transport contributions concentrated within the range of -5 to 0 μg·m-3. The vertical transport in the central and southern parts of the basin shows positive values, with transport contributions ranging from 0 to 10 μg·m-3, and the urban centre exhibits relatively stronger vertical transport with contributions ranging from 10 to 20 μg·m-3. Although the chemical formation contribution in the urban centre is relatively small due to high nitrogen oxide emissions, vertical and horizontal transport play significant roles and are among the key factors contributing to ozone pollution formation.

Characteristics of dielectric barrier discharge and ozone production in synthetic air

This work studies the characteristics of electrical discharge, optical emission spectroscopy and ozone production of an air-fed dielectric barrier discharge reactor. In particular, the reactor utilizes water as the high voltage electrode and the grounding electrode. Results show that when the applied peak-to-peak voltage is increased from 16.8 kV to 26.8 kV at 10 kHz, the specific input energy is increased from 19.0 J/L to 664.9 J/L. The maximum ozone generation efficiency reaches about 155 g/kWh with an ozone concentration of around 1549 ppm. The results also show that at a peak-to-peak voltage of 24.0 kV, the typical rotational temperature is 306 ± 5 K. In addition, during a 400 min stability test with ozone concentrations up to about 6000 ppm, the ozone generation efficiency is stabilized at around 106 g/kWh. The reactor can provide optimized control of the gas temperature and realizes energy-efficient ozone generation.

Observation-Based Ozone Formation Rules by Gradient Boosting Decision Trees Model in Typical Chemical Industrial Parks

Ozone pollution in chemical industrial parks is severe and complicated and is significantly influenced by pollutant emissions and meteorological parameters. In this study, we innovatively investigated the formation rules of ozone by using observation-based analyses and a gradient-boosting decision tree (GBDT) model, focusing on a typical chemical industrial park located in the Yangtze River Delta of China. The results revealed that ozone concentration was positively correlated with temperature while negatively correlated with NO2 concentration and relative humidity (RH). Ozone pollution was predominantly observed from April to October (M4–10). The optimized GBDT model was subsequently utilized to establish a specific and quantifiable relationship between each single dominant impact factor (RH, NO2, temperature, and PM2.5) and ozone within a complex and uncertain multi-factor context during M4–10. Detailed discussions were conducted on the reaction rate of ozone-related to different levels of RH and temperature. The accumulation of ozone was favored by high temperature and low RH, with the maximum ozone concentration observed at the RH of 50% and the temperature of 35 °C. The NO2-O3 change curve exhibited distinct phases, including a period of stability, gradual increase, rapid increase, and equilibrium. During the second and third periods, the ratio of ozone production to NO2 consumption was 0.10 and 2.73, respectively. Furthermore, there was a non-monotonic relationship between variations in ozone concentration and PM2.5 concentration. Hence, it is imperative to implement fine control strategies in the park, such as adopting seasonal production strategies, implementing targeted measures for controlling NOx and active VOCs, and employing special control methods during periods of high temperature. This study provides aid in achieving effective management of localized ozone pollution and ensuring compliance with air quality standards.

Trends of surface ozone based on hourly concentrations in the Beijing–Tianjin–Hebei region during 2017–2021

As a typical secondary air pollutant, surface ozone has been monitored routinely since 2013 in China. Most studies on the spatiotemporal variation of ozone have been centered around the daily maximum 8-h average, with little attention paid to the trends of hourly ozone, especially hourly ozone exceedances. Focusing on hourly ozone exceedances and peak values, the spatiotemporal trends of hourly ozone at 77 sites in 13 cities of the Beijing–Tianjin–Hebei (BTH) region during 2017–2021 were analyzed in this study. The number of hours with exceedances (NH200) in 2019 was nearly three times that of 2021. On a five-year average, the percentage of cumulative NH200 in June accounted for up to 40.5 % of all hourly exceedances. Cities in central Hebei Province had the highest cumulative annual NH200. June had the highest average hourly ozone exceeded multiples of 0.158. The top two cities with the highest average exceeded multiple were Tangshan (0.166) and Beijing (0.158). Tangshan and Xingtai ranked as the top two in terms of the mean of the 10 highest daily maximum ozone concentrations (MTDM), with 286.74 and 285.37 µg m−3, respectively. The gap between the MTDM and the daily maximum of hourly ozone averaged over all sites had narrowed to 97.88 µg m−3 in 2021, much lower than that in other years, which indicated that the stability and convergence of ozone pollution in BTH region had been enhanced in 2021 to some extent.摘要本文以京津冀地区为研究对象, 采用国际常用的评价指标, 在分析2017–2021年臭氧小时浓度变化趋势的基础上, 重点讨论了小时浓度超标情况及其峰值水平. 结果显示, 2019年臭氧小时浓度超标数约为2021年的3倍, 6月份小时浓度超标数占比高达40.5%, 河北中部城市小时浓度超标情况突出; 2017年和2019年臭氧小时浓度超标倍数在高位区间的占比相对最高, 唐山和邢台的小时浓度峰值水平相对较高. 本文可为后续进一步研究局地臭氧污染特征和异常污染事件提供基础参考.

Distribution of ozone, carbon monoxide and oxides of nitrogen over an urban location in the foothills of the North-Western Himalayas

Increasing anthropogenic activities and biomass burning events over the Northern Indian region severely affect the pristine environment of North-Western Himalayas. To investigate their influence in this data sparse region, continuous monitoring of O3, CO and NOx are made during January 2018 to December 2019 over Dehradun, an urban location in the foothills of North-western Himalayas. Ozone shows daytime broad peak and CO and NOx show two peaks during morning and evening hours. The maximum daytime ozone is observed during spring with 58.2 ± 2.0 ppbv (56.2 ± 2.7 ppbv) during 2018 (2019). CO and NOx show maximum value during winter and minimum during summer-monsoon. Their concentrations are found to be influenced from stubble burning and forest fire emissions during late spring. WRF-Chem simulations are made with and without biomass burning emissions to quantify the contribution of these emissions on the variability of these gases over Dehradun. Sensitivity simulations reveal that biomass burning over northern Indian region contributed 43 ppbv, 79 ppbv and 1.2 ppbv increase in O3, CO and NOx mixing ratios over Dehradun. In addition, dust storm event in June 2018 contributed for lower ozone levels in 2018 (16.1 ± 9.3 ppbv) and stratosphere troposphere exchange process enhanced surface ozone in June 2019 (53.6 ± 22.3 ppbv).

Tropospheric Ozone levels in and around southern city Bengaluru, India

The diurnal to seasonal ozone (O3) pre-cursors (NO, NO2, CO, VOCs) trends over local climatic zones (LCZs) with the changes in weather patterns with respect to land cover classes determines the O3 trends and useful for air quality management. In this work, diurnal to seasonal patterns of O3 concentrations are analysed across the different LCZs in Bengaluru region. The Central/State Pollution Control Boards (CPCB/SPCB) operate more than 500 continuous air quality and weather monitoring stations across the India. Hourly O3 concentration data were collected from CPCB for 5 different LCZs within the Bengaluru region over a period of four years (2019-2022). Time series analyses were conducted to examine the temporal variations in O3 levels. The results showed significant fluctuations in diurnal trends of O3 due to the influence of air temperature and relative humidity variations across the five LCZs within Bengaluru region. There were distinct seasonal trends in O3 concentrations with maximum (60-65 ppb) observed during the winter and summer seasons and that of minimum concentration in the range 20-25 ppb during the monsoon months. The observed maximum ozone levels (60 -65 ppb) found to be beyond the threshold national ambient air quality standard (NAAQ) and the accumulation exposure over threshold of 40 ppb (AOT 40) during the winter and summer. The O3 concentration trends are in line with the published research on premature mortality about 1200 annually for Karnataka state for chronic obstructive pulmonary disease owing to population exposure to O3 beyond its threshold level of NAAQ. Also, the annual rice yield loss is about 2% (~0.1 Metric Tonne) with the AOT 40 to paddy crop for Karnataka state. Thus, O3 diurnal to seasonal trends serve the first-hand information to local authorities for the action plan of air quality management taking into consideration O3 precursors, wind speed, and wind direction.

ТЕОРЕТИЧЕСКИЕ ПРЕДПОСЫЛКИ ОПРЕДЕЛЕНИЯ РАЗМЕРА И ОБЪЁМА РАСПРОСТРАНЕНИЯ ОЧАГА ОЗОНА В ЗЕРНОВОМ ВОРОХЕ И ОПТИМИЗАЦИЯ ВРЕМЕНИ ОЗОНИРОВАНИЯ

One of the most promising methods for processing agricultural products today is the ozonation process. The effect of ozone on grain will allow it to be disinfected and stimulate the growth processes of the seed, without causing harmful emissions into the environment. The purpose of the research was to find the optimal time for ozonation of grain and seeds depending on the processing speed of a certain volume of grain material. To achieve it, numerical optimization methods were used, namely the patternsearch global search method, which will determine the most rational ozonation regime for given conditions, were used to achieve it. The source of ozone propagation in a grain heap during ozonation for 10...60 minutes is close in shape to an ellipsoid, but has a slightly different mathematical description. The mathematical models obtained by interpolation make it possible to determine the minimum ozonation time and the maximum speed of ozone treatment per unit volume of a grain heap. It was revealed that increasing the processed volume of grain due to the longer duration of the operation does not make sense, as it will contribute to an increase in energy and cost costs. Under given conditions, an ozonation time of 1270 seconds provides a maximum ozone treatment rate of 3059 mm3/s per unit volume of grain. Optimization will make it possible to ozone the maximum volume of a grain storage facility as quickly as possible at minimal cost. The shortest processing time per unit volume under these conditions was 0.000327 s/mm3. Other ozonation parameters will have different optimal values, therefore the proposed methodology is the basis of an appropriate computer program that will automatically determine the optimal ozonation regime for specific conditions.

Measurement and Risk Analysis of Ozone (O3) Concentrations in the 9 MeV and 12 MeV Electron Mode LINAC

This study investigates potential non-radiation hazards, specifically Ozone (O3) production, during Linear Accelerator (LINAC) electron mode radiotherapy. The research uses experimental measurements to determine Ozone concentration in the LINAC patient waiting room and control room. Measurements are taken assuming a ±2-hour delay in one working day, using 9 MeV and 12 MeV energy, 400 MU dose rate, and illumination angles of 0o, 90o, and 270o. Maximum Ozone concentrations in the LINAC patient waiting room and control room are found to be 6.6 ppb (12 MeV) and 8.3 ppb (12 MeV), respectively. These concentrations fall below the chemical threshold limit and are deemed safe for human exposure. Notably, potentially detectable Ozone levels are observed in the LINAC banker. Overall, this research highlights the importance of monitoring Ozone levels to ensure the safety of both patients and personnel in LINAC facilities.

Applicability of evaluation metrics/schemes for human health burden attributable to regional ozone pollution: A case study in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), South China

This is a study to identify the applicable/preferable short- and long-term metrics/schemes to evaluate the premature mortality attributable to the ozone pollution in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), one of the most representative populous ozone pollution regions in China, by comprehensively accounting the uncertainty sources. The discrepancy between the observation and the CAQRA reanalysis datasets (2013–2019) was investigated in terms of the concentration variation pattern, which determines the exposure metric change. A set of domestic short-term C-R coefficients for the all-age population were integrated using the meta-analysis respectively corresponding to the metrics of MDA1, MDA8, and Daily average. The dataset-based deviations of the short-term attributable factors (AFs) and their corresponding premature mortalities were respectively about 16.9 ± 13.3 % and <5 % based on MDA8, much smaller than other two metrics; and the MDA8-based evaluation results were the most sensitive to the deteriorative ozone pollution, with the maximum upward trends of 0.095–0.129 %/year. Accordingly, MDA8 was recognized as the most applicable short-term metric. For the long-term exposure, the domestic summer metric SMDA8 could not exactly represent the peak-season ozone maximum level in the GBA, with the deviation from 6MMDA8 as much as 30 %. By considering the ability of metric to represent the peak-season ozone, the relatively smaller dataset-based discrepancies of AFs (6MMDA8-WHO2021: 23.3 ± 16.9 %, AMDA8-T2016: 20.7 ± 15.8 %) and the attributable premature mortalities (6MMDA8-WHO2021: 5 %, AMDA8-T2016: 8 %), and the higher sensitivity of the evaluation results to the deteriorative ozone pollution (6MMDA8-WHO2021: 0.13 %;year, p = 0.01; AMDA8-T2016: 0.15 %/year, p = 0.03), the schemes of 6MMDA8-WHO2021 and AMDA8-T2016 were recognized relatively more preferable for the adult (≥25-year) long-term evaluation. Based on the recognized metric/schemes, the central and the eastern PRE areas of higher NO2 level in the GBA were experiencing the highest health burdens from 2013 to 2019.

Examining modification of the associations between air pollution and birth outcomes by neighborhood deprivation in a North Carolina birth cohort, 2011-2015.

Evidence from studies of air pollutants and birth outcomes suggests an association, but uncertainties around geographical variability and modifying factors still remain. As neighborhood-level social characteristics are associated with birth outcomes, we assess whether neighborhood deprivation level is an effect measure modifier on the association between air pollution and birth outcomes in a North Carolina birth cohort. Using birth certificate data, all North Carolina residential singleton live births from 1 January 2011 to 31 December 2015 with gestational ages of 20-44 weeks (n = 566,799) were examined for birth defect diagnoses and preterm birth. Exposures were daily average fine particulate matter (PM2.5), daily 8-h maximum nitrogen dioxide (NO2), and daily 8-h maximum ozone (O3) modeled concentrations, and the modifier of interest was the neighborhood deprivation index (NDI). Linear binomial models were used to estimate the prevalence differences and 95% confidence intervals (CI) for the association between ambient air pollution and birth defect diagnoses. Modified Poisson regression models were used to estimate risk differences (RDs) and 95% CIs for air pollution and preterm birth. Models were stratified by the neighborhood deprivation index group (low, medium, or high) to assess potential modification by NDI. Approximately 3.1% of the study population had at least one birth defect and 8.18% were born preterm. For preterm birth, associations with PM2.5 and O3 did not follow a conclusive pattern and there was no evidence of modification by NDI. The associations between NO2 and preterm birth were generally negative across exposure windows except for a positive association with NO2 and preterm birth for high NDI [RD: 34.70 (95% CI 4.84-64.56)] for entire pregnancy exposure. There was no evidence of associations between pollutants examined and birth defects. There may be differences in the association between NO2 exposure and preterm birth by NDI but we did not observe any evidence of associations for birth defects. Our results support the public health protection afforded by reductions in air pollution, even in areas of neighborhood deprivation, but future research conducted in areas with higher levels of air pollution and evaluating the potential for modification by neighborhood deprivation level would be informative.

Stratospheric Temperature and Ozone Impacts of the Hunga Tonga‐Hunga Ha'apai Water Vapor Injection

AbstractThe January 2022 eruption of the Hunga Tonga‐Hunga Ha'apai underwater volcano injected a large amount of water vapor into the mid‐stratosphere. This study uses model simulations to investigate the resulting stratospheric impacts out to 2031. Maximum radiatively‐driven model temperature changes occur in the Southern Hemisphere (SH) subtropics in April–May 2022, with warming of ∼1 K in the lower stratosphere and cooling of 3 K in the mid‐stratosphere. The radiative cooling combined with adiabatic cooling driven by the quasi‐biennial oscillation meridional circulation explains the near‐record cold anomaly observed in the SH subtropical mid‐stratosphere. Projected ozone responses maximize in 2023–2024 as the water vapor plume is transported globally throughout the stratosphere and mesosphere. The excess H2O increases the OH radical, causing a negative global ozone response (2%–10%) in the upper stratosphere and mesosphere due to increased odd hydrogen‐ozone loss, and a small positive ozone response (0.5%–1%) in the mid‐stratosphere due to interference of the NOx catalytic loss cycle by the additional OH. In the lower stratosphere, the excess H2O is projected to increase polar stratospheric clouds and springtime halogen‐ozone loss, enhancing the Antarctic ozone hole by 25–30 DU in 2023. Arctic impact is small, with maximum additional ozone loss of 4–5 DU projected in spring 2024. These responses diminish after 2024 to be quite small by 2031, as the excess H2O is removed from the stratosphere with a 2.5‐year e‐folding time. Given the year‐to‐year variability of the stratosphere, the magnitudes of these ozone responses may be below the threshold of detectability in observations.

Implementation and evaluation of updated photolysis rates in the EMEP MSC-W chemistry-transport model using Cloud-J v7.3e

Abstract. The present work describes the implementation of the state of the art Cloud-J v7.3 photolysis rate calculation code in the EMEP MSC-W chemistry-transport model. Cloud-J calculates photolysis rates and accounts for cloud and aerosol optical properties at model run time, replacing the old system based on tabulated values. The performance of Cloud-J is evaluated against aerial photolysis rate observations made over the Pacific Ocean and against surface observations from three measurement sites in Europe. Numerical experiments are performed to investigate the sensitivity of the calculated photolysis rates to the spatial and temporal model resolution, input meteorology model, simulated ozone column, and cloud effect parameterization. These experiments indicate that the calculated photolysis rates are most sensitive to the choice of input meteorology model and cloud effect parameterization while also showing that surface ozone photolysis rates can vary by up to 20 % due to daily variations in total ozone column. Further analysis investigates the impact of Cloud-J on the oxidizing capacity of the troposphere, aerosol–photolysis interactions, and surface air quality predictions. Results find that the annual mean mass-weighted tropospheric hydroxyl concentration is increased by 26 %, while the photolytic impact of aerosols is mostly limited to large tropical biomass-burning regions. Overall, Cloud-J represents a major improvement over the tabulated system, leading to improved model performance for predicting carbon monoxide and daily maximum ozone surface concentrations.

Trends in polar ozone loss since 1989: potential sign of recovery in the Arctic ozone column

Abstract. Ozone depletion over the polar regions is monitored each year by satellite- and ground-based instruments. In this study, the vortex-averaged ozone loss over the last 3 decades is evaluated for both polar regions using the passive ozone tracer of the chemical transport model TOMCAT/SLIMCAT and total ozone observations from Système d'Analyse par Observation Zénithale (SAOZ) ground-based instruments and Multi-Sensor Reanalysis (MSR2). The passive-tracer method allows us to determine the evolution of the daily rate of column ozone destruction and the magnitude of the cumulative column loss at the end of the winter. Three metrics are used in trend analyses that aim to assess the ozone recovery rate over both polar regions: (1) the maximum ozone loss at the end of the winter, (2) the onset day of ozone loss at a specific threshold, and (3) the ozone loss residuals computed from the differences between annual ozone loss and ozone loss values regressed with respect to sunlit volume of polar stratospheric clouds (VPSCs). This latter metric is based on linear and parabolic regressions for ozone loss in the Northern Hemisphere and Southern Hemisphere, respectively. In the Antarctic, metrics 1 and 3 yield trends of −2.3 % and −2.2 % per decade for the 2000–2021 period, significant at 1 and 2 standard deviations (σ), respectively. For metric 2, various thresholds were considered at the total ozone loss values of 20 %, 25 %, 30 %, 35 %, and 40 %, all of them showing a time delay as a function of year in terms of when the threshold is reached. The trends are significant at the 2σ level and vary from 3.5 to 4.2 d per decade between the various thresholds. In the Arctic, metric 1 exhibits large interannual variability, and no significant trend is detected; this result is highly influenced by the record ozone losses in 2011 and 2020. Metric 2 is not applied in the Northern Hemisphere due to the difficulty in finding a threshold value in enough of the winters. Metric 3 provides a negative trend in Arctic ozone loss residuals with respect to the sunlit VPSC fit of −2.00 ± 0.97 (1σ) % per decade, with limited significance at the 2σ level. With such a metric, a potential quantitative detection of ozone recovery in the Arctic springtime lower stratosphere can be made.

Determination of Total Stratospheric Ozone on Millimeter Waveband over the Central Asian Region

The principles of operation of the main blocks of the radio spectrometer of the millimeter range for the study of the ozone layer are presented. Some results of measurements of the altitude distribution of ozone over the region of Central Asia are presented, according to which the zones of maximum ozone concentration in height are confirmed, and total ozone is determined in the altitude range of 20‑60 km.