Ozone Variations Research Articles

Changes in US background ozone associated with the 2011 turnaround in Chinese NOx emissions

Assessing the effectiveness of surface ozone air quality regulations is complicated by non-local sources and inhibited by sparse in situ observational networks. Here, we harness satellite measurements of ozone and its precursors over Asia to identify the Asian contribution to background ozone over the United States (US) from 2006-2016 using a state-of-the-art chemical data assimilation system. Our results indicate that Chinese NOx emissions reached an apex in 2011, increasing daily average ozone concentrations over Los Angeles by up to 3.8 ppb at 750 hPa and 0.7 ppb at the surface in 2012 relative to 2006, with somewhat larger impacts in the high altitude regions of the Western US (assuming constant VOC emissions). Decreasing Chinese NOx emissions after 2011 contributed to a reduction of similar magnitude in Western US background ozone from 2012-2016. We also assess the impact of direct assimilation of satellite-based tropospheric ozone profile measurements over Asia and find that it substantially modifies global ozone, including US surface concentrations. These results suggest that measurements of both ozone and its precursors over Asia play a substantial role in evaluating not only local but also global air quality. The simultaneous assimilation of ozone and its precursors proffers a powerful way to constrain the vertical profile of ozone and improve understanding of ozone variations. In the future, a more extensive satellite observing system has great potential to better constrain both local pollution and background ozone globally when employed in conjunction with chemical data assimilation.

The impact of peripheral circulation characteristics of typhoon on sustained ozone episodes over the Pearl River Delta region, China

Abstract. The peripheral circulation of typhoon forms sustained ozone episodes. However, how it impacts the day-to-day ozone pollution levels during the episodes has not been clearly studied, which is crucial for better prediction of the daily ozone variation. In this study, the analysis of ground observation, wind profile data, and model simulation is integrated. By analysing the wind profile radar observations, we found a weak wind deepening (WWD; vertical depth of the weak winds increased), more correlated with the ground-level ozone variation than surface weak wind. Long-term statistical analyses showed that the WWD is a common weather phenomenon in the peripheral subsidence region of typhoons and is generally accompanied by ozone pollution episodes. The Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) with process analysis simulation showed that the peripheral subsidence chemical formation (CHEM) and vertical mixing (VMIX) effects are two major contributors to the enhancement of ozone levels to form the episode, while the advection (ADV) showed negative values. However, the day-to-day variation of the daytime ozone levels during the episode is not determined by the daily variation of daytime CHEM and VMIX but is dominated by the ADV terms. Therefore, the ozone and its precursors accumulation, including the enhancement during the night-time, contribute to the daytime ozone increase in the following day. A detail day-to-day process analysis showed that in additional to decrease of negative ADV values (e.g. the weakened advection outflow or dispersion) on the ground, the integrated effect of the daily variation of the accumulative CHEM and ADV above the ground throughout the planetary boundary layer (PBL) together determined the overall day-to-day daytime ozone variation on the ground through the VMIX process. The results indicate that the peripheral characteristics of approaching typhoon not only form the ozone episode by the enhanced photochemical reactions, but also could increase the day-to-day daytime ozone levels via pollution accumulation throughout the PBL due to the WWD up to 3–5 km. These results illustrate the important role of the WWD in the lower troposphere for the formation of sustained ozone episodes due to the peripheral circulation of the typhoon, which helps to better predict the daily changes of daytime ozone levels.

Ozone Monitoring in the Baikal Region (East Siberia): Spatiotemporal Variability under the Influence of Air Pollutants and Site Conditions

This article analyses the results of year-round automatic ozone monitoring in seven cities of the Baikal region (southeastern Siberia). We reveal that significant differences in the spatiotemporal variability of the average daily ozone concentrations depend on different anthropogenic loads. In large cities with heavy industry, which are located in the Angara River valley, the ozone concentrations were minimal and changed little during the year: less than 5 µg/m3 in the Angarsk city and 20–30 µg/m3 in the Irkutsk city. In the settlements of a less polluted region, the Selenga River valley, the ozone concentrations were significantly higher, and the annual ozone variability was typical of East Siberia: the maximum in spring (60 to 70 μg/m3) and the minimum in autumn and winter (10 to 30 μg/m3). The maximum ozone concentrations were observed in rural conditions (Listvyanka station), up to 80–100 μg/m3 during the spring maximum. Nitrogen oxides had the main influence on ozone depletion in the surface atmosphere of the cities, especially in winter, the season of maximum burning of fossil fuels (negative correlation can reach −0.9). In cities with heavy industry, the effect of NOx on ozone was weaker. Perhaps other anthropogenic impurities can also affect ozone suppression in these cities, which have not yet been studied.

A comparison of the impact of TROPOMI and OMI tropospheric NO<sub>2</sub> on global chemical data assimilation

Abstract. This study gives a systematic comparison of the Tropospheric Monitoring Instrument (TROPOMI) version 1.2 and Ozone Monitoring Instrument (OMI) QA4ECV tropospheric NO2 column through global chemical data assimilation (DA) integration for the period April–May 2018. DA performance is controlled by measurement sensitivities, retrieval errors, and coverage. The smaller mean relative observation errors by 16 % in TROPOMI than OMI over 60∘ N–60∘ S during April–May 2018 led to larger reductions in the global root-mean-square error (RMSE) against the assimilated NO2 measurements in TROPOMI DA (by 54 %) than in OMI DA (by 38 %). Agreements against the independent surface, aircraft-campaign, and ozonesonde observation data were also improved by TROPOMI DA compared to the control model simulation (by 12 %–84 % for NO2 and by 7 %–40 % for ozone), which were more obvious than those by OMI DA for many cases (by 2 %–70 % for NO2 and by 1 %–22 % for ozone) due to better capturing spatial and temporal variability by TROPOMI DA. The estimated global total NOx emissions were 15 % lower in TROPOMI DA, with 2 %–23 % smaller regional total emissions, in line with the observed negative bias of the TROPOMI version 1.2 product compared to the OMI QA4ECV product. TROPOMI DA can provide city-scale emission estimates, which were within 10 % differences with other high-resolution analyses for several limited areas, while providing a globally consistent analysis. These results demonstrate that TROPOMI DA improves global analyses of NO2 and ozone, which would also benefit studies on detailed spatial and temporal variations in ozone and nitrate aerosols and the evaluation of bottom-up NOx emission inventories.

Multi-Year Variation of Ozone and Particulate Matter in Northeast China Based on the Tracking Air Pollution in China (TAP) Data.

With the rapid development of economy and urbanization acceleration, ozone (O3) pollution has become the main factor of urban air pollution in China after particulate matter. In this study, 90th percentile of maximum daily average (MDA) 8 h O3 (O3-8h-90per) and PM2.5 data from the Tracking Air Pollution in China (TAP) dataset were used to determine the mean annual, seasonal, monthly, and interannual distribution of O3-8h-90per and PM2.5 concentrations in Northeast China (NEC). The O3-8h-90per concentration was highest in Liaoning (>100 μg/m3), whereas the highest PM2.5 concentration was observed mainly in urban areas of central Liaoning and the Harbin–Changchun urban agglomeration (approximately 60 μg/m3). The O3-8h-90per concentrations were highest in spring and summer due to more intense solar radiation. On the contrary, the PM2.5 concentration increased considerably in winter influenced by anthropogenic activities. In May and June, the highest monthly mean O3-8h-90per concentrations were observed in central and western Liaoning, about 170–180 μg/m3, while the PM2.5 concentrations were the highest in January, February, and December, approximately 100 μg/m3. The annual mean O3-8h-90per concentration in NEC showed an increasing trend, while the PM2.5 concentration exhibited an annual decline. By 2020, the annual mean O3-8h-90per concentration in southern Liaoning had increased considerably, reaching 120–130 μg/m3. From the perspective of city levels, PM2.5 and O3-8h-90per also showed an opposite variation trend in the 35 cities of NEC. The reduced tropospheric NO2 column is consistent with the decreasing trend of the interannual PM2.5, while the increased surface temperature could be the main meteorological factor affecting the O3-8h-90per concentration in NEC. The results of this study enable a comprehensive understanding of the regional and climatological O3-8h-90per and PM2.5 distribution at distinct spatial and temporal scales in NEC.

Variations of Arctic winter ozone from the LIMS Level 3 dataset

Abstract. The Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) instrument operated from 25 October 1978 through 28 May 1979. Its Version 6 (V6) profiles and their Level 3 or zonal Fourier coefficient products have been characterized and archived in 2008 and in 2011, respectively. This paper focuses on the value and use of daily ozone maps from Level 3, based on a gridding of its zonal coefficients. We present maps of V6 ozone on pressure surfaces and compare them with several rocket-borne chemiluminescent ozone measurements that extend into the lower mesosphere. We illustrate how the synoptic maps of V6 ozone and temperature are an important aid in interpreting satellite limb-infrared emission versus local measurements, especially when they occur during dynamically active periods of Northern Hemisphere winter. A map sequence spanning the minor stratospheric warmings of late January and early February characterizes the evolution of a low-ozone pocket (LOP) at that time. We also present time series of the wintertime tertiary ozone maximum and its associated zonally varying temperatures in the upper mesosphere. These examples provide guidance to researchers for further exploratory analyses of the daily maps of middle atmosphere ozone from LIMS.

The dynamical evolution of Sudden Stratospheric Warmings of the Arctic winters in the past decade 2011\u20132021

In this study, we analyse the dynamical evolution, and identify the major warming (MW) and minor warming events of the past 11 Arctic winters (2010/11–2020/21). During the period, MW is found in 4 winters and is in January for 2012/13, 2018/19 and 2020/21 and in February for 2017/18. A major final warming is observed in the year 2015/16. The most severe MW occurred in the 2012/13 winter, for which a rise in temperature of about 30 K is found at 60° N. The investigation of tropospheric wave forcings for the period reveals that the MW in 2012/13 and 2017/18 is forced by the combined activity of waves 1 and 2, whereas the MW in 2018/19 and 2020/21 is driven by wave 1. Studies have shown that the frequency of Sudden Stratospheric Warming (SSW) in the Arctic has been increasing since 1957/58, which is about 1.1 MWs/winter during 1998/99–2009/10. However, this frequency decreases to 0.36 MWs/winter in the period 2010/11–2020/21 and 0.74 MWs/winter in 1998/99–2020/21. An inverse relationship is observed between the period of occurrence of SSWs and total column ozone (TCO) in the Arctic for the past 11 winters (2010/11–2020/21). For instance, the temperature in the lower stratosphere in January, in which most warmings occur, shows a statistically significant high positive correlation (0.79) with the average TCO in January–March. Therefore, this study assists in understanding the relationship between inter-annual variability of ozone and the occurrence of SSWs.

Multi-year variation of near-surface ozone at Zhongshan Station, Antarctica

With the support of the Chinese National Antarctic Research Expedition, near-surface ozone (O3) was continuously monitored at Zhongshan Station (ZOS) (69°22′12″ S, 76°21′49″ E, 18.5 m above sea level) in East Antarctica from 2008 to 2020. The seasonal and diurnal variability of near-surface O3 at ZOS were investigated. O3 enhancement events (OEEs) were frequently observed in the warm season (OEEs in January accounted for 23.0% of all OEEs). The OEEs at ZOS were related to the photochemical reaction processes under the influences of O3 and solar radiation in the stratosphere and synoptic-scale air mass transport from coastal areas (Princess Elizabeth Land, Wilkes Land, and Queen Mary Land), as evidenced by the recorded wind speed, solar shortwave irradiance, and total column ozone data and the computed potential source contribution function and concentration-weighted trajectory models. The results computed by the tool Stratosphere-to-Troposphere Exchange Flux indicated that stratosphere-to-troposphere transport had no direct impact on OEEs at ZOS. Therefore, synoptic-scale air mass transport is the main cause of OEEs in Antarctica, which is consistent with previous studies. Unlike OEEs at inland Antarctic stations, which are mainly affected by air mass transport from inland plateaus, OEEs at ZOS, a coastal station, are mainly affected by air mass transport from coastal land in East Antarctica.

Variation of Ozone in the Pantanal Environment Based on Probability Distributions

ABSTRACT The tropospheric ozone column (O3) plays a fundamental role in terrestrial life, particularly in climate variability, and protects the terrestrial biosphere from ultraviolet (UV) radiation. The study investigates the variation of the O3 concentration column in the Pantanal based on probability distributions. The adequacy of the Log Normal (LN), GUM (Gumbel) and GEV (Generalized Extreme Values) distributions were tested using the Kolmogorov-Smirnov (KS), D (Anderson-Darling), AIC (Akaike Information Criterion), BIC (Bayesian Information Criterion), R2(coefficient of determination) and RMSE (root mean square error) tests in the period from 2005 to 2020. In most months investigated, the Pantanal follows the GUM and GEV probability distributions. In addition, monthly means of O3 and standard deviations were calculated. It is worth mentioning the variability of O3 and the impact on climate change.

Impact of the COVID‐19 Economic Downturn on Tropospheric Ozone Trends: An Uncertainty Weighted Data Synthesis for Quantifying Regional Anomalies Above Western North America and Europe

This study quantifies the association between the COVID‐19 economic downturn and 2020 tropospheric ozone anomalies above Europe and western North America, and their impact on long‐term trends. Anomaly detection for an atmospheric time series is usually carried out by identifying potentially aberrant data points relative to climatological values. However, detecting ozone anomalies from sparsely sampled ozonesonde profiles (once per week at most sites) is challenging due to ozone's high temporal variability. We first demonstrate the challenges for summarizing regional trends based on independent time series from multiple nearby ozone profiling stations. We then propose a novel regional‐scale anomaly detection framework based on generalized additive mixed models, which accounts for the sampling frequency and inherent data uncertainty associated with each vertical profile data set, measured by ozonesondes, lidar or commercial aircraft. This method produces a long‐term monthly time series with high vertical resolution that reports ozone anomalies from the surface to the middle‐stratosphere under a unified framework, which can be used to quantify the regional‐scale ozone anomalies during the COVID‐19 economic downturn. By incorporating extensive commercial aircraft data and frequently sampled ozonesonde profiles above Europe, we show that the complex interannual variability of ozone can be adequately captured by our modeling approach. The results show that free tropospheric ozone negative anomalies in 2020 are the most profound since the benchmark year of 1994 for both Europe and western North America, and positive trends over 1994–2019 are diminished in both regions by the 2020 anomalies.

Surface ozone impacts on major crop production in China from 2010 to 2017

Abstract. Exposure to elevated surface ozone is damaging to crops. In this study, we performed an analysis of temporal and spatial distributions of relative yield losses (RYLs) attributable to surface ozone for major crops in China from 2010 to 2017, by applying AOT40 metrics (hourly ozone concentration over a threshold of 40 ppbv during the growing season) simulated using a chemical transport model. The major crops in China include wheat, rice (including double early and late rice, and single rice), maize (including north and south maize), and soybean. The aggregated production and associated economic losses in China and major provinces were evaluated by combing annual crop production yields and crop market prices. We estimated that the national annual average AOT40 in China increased from 21.98 ppm h in 2010 to 23.85 ppm h in 2017, with a peak value of 35.69 ppm h in 2014, as simulated with the model. There is significant spatial heterogeneity for the AOT40 and RYLs across the four crops due to the seasonal ozone variations. We calculated that national mean RYLs for wheat, rice, maize, and soybean were 11.45 %–19.74 %, 7.59 %–9.29 %, 0.07 %–3.35 %, and 6.51 %–9.92 %, respectively, from 2010 to 2017. The associated crop yield losses were estimated at 13.81–36.51, 16.89–20.03, 4.59–8.17, and 1.09–1.84 million metric tons (Mt) respectively, which accounted for annual average economic loss of USD 9.55 billion, USD 8.53 billion, USD 2.23 billion, and USD 1.16 billion individually over the 8 years. Our study provides the first long-term quantitative estimation of crop yield losses and their economic cost from surface ozone exposure in China before and after the China Clean Air Act in 2013, and improves understanding of the spatial sensitivity of Chinese crops to ozone impacts.

Temporal and Spatial Variations in Ozone and Its Causes over Hainan Province from 2015 to 2020

This study investigated temporal and spatial variations in O3-8h (defined as the maximum 8 h average result) in Hainan Province from 2015 to 2020 and further analyzed its relationships with precursors and meteorological factors based on a dataset of observations from 32 environmental monitoring stations in Hainan. Basic statistical methods, including the empirical orthogonal function (EOF), climatic tendency rate, and climatic trend coefficient analysis, were used here. The results showed that ρ(O3-8h) was higher in northern and western Hainan than that in other regions, with the maximum value occurring in Dongfang City (91.5 μg·m-3). Twelve cities and counties experienced a downward trend from 2015 to 2020, and six cities and counties reached a 95% confidence level. The variation in ρ(O3-8h) in Hainan Province demonstrated remarkable seasonal changes, which were the largest in the autumn, spring, and winter followed by the smallest in the summer, exhibiting a clear declining trend in all seasons except autumn. In addition, the cumulative variance of the first two eigenvector fields decomposed by EOF was 72.58%, which could well describe the distributed characteristics of ρ(O3-8h) in Hainan Province. The first mode reflected the consistency of ρ(O3-8h) variation, and the second mode reflected regional differences. Meanwhile, the change in ρ(O3-8h) had a good correlation with the precursors and meteorological factors. Among them, the correlation coefficients between ρ(O3-8h) and ρ(NO2), precipitation, sunshine duration, average temperature, average wind speed, atmospheric pressure, and total radiation passed the 99% confidence test. The results of multiple linear regression showed that the variation in regressed ρ(O3-8h) was consistent with the observed ρ(O3-8h), and the correlation coefficient between them was 0.853, which passed the 99.9% confidence test. The regression value explained 0.72 variance of the observed value.

An intercomparison of ozone taken from the Copernicus atmosphere monitoring service and the second Modern-Era retrospective analysis for research and applications over China during 2018 and 2019

Spatiotemporal variations of ozone (O3) taken from the Copernicus Atmosphere Monitoring Service (CAMS) and the second Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) were intercompared and evaluated with ground and ozone-sonde observations over China in 2018 and 2019. Intercomparison of the surface ozone from CAMS and MERRA-2 reanalysis showed significant negative bias (CAMS minus MERRA-2, same below) at Tibetan Plateau of up to 80 µg/m3, and the average R2 was about 0.6 across China. Evaluated with the ground observations from China National Environmental Monitoring Center (CNEMC), we found that CAMS and MERRA-2 reanalysis were capable of capturing the key patterns of monthly and diurnal variations of surface ozone over China except for the western region, and MERRA-2 overestimated the observations compared to CAMS. Vertically, the CAMS profiles overestimated the ozone-sonde from the World Ozone and Ultraviolet Radiation Data Center (WOUDC) above 200 hPa with the magnitude reaching up to 150 µg/m3, while little bias was found between the reanalysis and observations below 200 hPa. Intercomparison drawn from the vertical distribution between CAMS and MERRA-2 reanalysis showed that the negative bias appeared throughout the troposphere over China, while the positive bias emerged in the upper troposphere and lower stratosphere (UTLS) with high order of magnitude exceeding 100 µg/m3, indicating large uncertainties at higher altitudes. In summary, we concluded that CAMS reanalysis showed better agreement with the observations in contrast to MERRA-2, and the large discrepancy especially at higher altitudes between these two reanalysis datasets could not be ignored.

Long-term measurements of ground-level ozone in Windsor, Canada and surrounding areas

This study investigated temporal variability of ground-level ozone (O3) during smog season in Windsor, Canada and surrounding states of the US during 1996–2015. Cluster analysis classified six sites into two groups with similar features of O3 concentrations. The first group consists of four urban/suburban sites, Windsor, Allen Park and Lansing in Michigan, and Erie in Ohio, and the second group includes two rural sites, Delaware and National Trail School in Ohio. The similarities among all six sites include (1) diurnal and seasonal variability of O3 concentrations owing to similar weather conditions, and (2) decreasing peak O3 (95th percentile) concentrations due to reduced emissions of precursors, thus less photochemical O3 formation. However, how O3 levels changed with reduced NOX emissions during the study period and on weekends differed between the two groups. Lower O3 concentrations were recorded at urban/suburban sites (30 ppb) than at rural sites (34 ppb). At urban sites, annual smog season O3 concentrations increased by 0.12–3.2 ppb/year. The increasing trends occurred at all percentile levels except for 95th percentile and in most months, due to weakened NO titration effect. At the rural sites, smog-season O3 concentrations decreased by 0.01–2.71 ppb/year. The decreasing trends were observed at 50-95th percentile levels and in most months. Between the two groups, the urban/suburban group had a greater increment in weekend O3 concentrations (3.3 vs. 1.6 ppb) due to a greater reduction of local NO emissions on weekend, thus, weakened NO titration effect. Overall, O3 formation was more sensitive to VOCs during the study period; however, the O3 formation regime gradually shifted toward more sensitive to NOX during 1996–2007 then became more sensitive to VOCs during 2008–2015. Therefore, controlling anthropogenic VOC emissions is needed to effectively mitigate O3 pollution in the study region.

A New Index Developed for Fast Diagnosis of Meteorological Roles in Ground-Level Ozone Variations.

China experienced worsening ground-level ozone (O3) pollution from 2013 to 2019. In this study, meteorological parameters, including surface temperature (T2), solar radiation (SW), and wind speed (WS), were classified into two aspects, (1) Photochemical Reaction Condition (PRC = T2 × SW) and (2) Physical Dispersion Capacity (PDC = WS). In this way, a Meteorology Synthetic Index (MSI = PRC/PDC) was developed for the quantification of meteorology-induced ground-level O3 pollution. The positive linear relationship between the 90th percentile of MDA8 (maximum daily 8-h average) O3 concentration and MSI determined that the contribution of meteorological changes to ground-level O−3 varied on a latitudinal gradient, decreasing from ∼40% in southern China to 10%–20% in northern China. Favorable photochemical reaction conditions were more important for ground-level O3 pollution. This study proposes a universally applicable index for fast diagnosis of meteorological roles in ground-level O3 variability, which enables the assessment of the observed effects of precursor emissions reductions that can be used for designing future control policies.Electronic Supplementary MaterialSupplementary material is available in the online version of this article at 10.1007/s00376-021-1257-x.

A single-peak-structured solar cycle signal in stratospheric ozone based on Microwave Limb Sounder observations and model simulations

Abstract. Until now our understanding of the 11-year solar cycle signal (SCS) in stratospheric ozone has been largely based on high-quality but sparse ozone profiles from the Stratospheric Aerosol and Gas Experiment (SAGE) II or coarsely resolved ozone profiles from the nadir-viewing Solar Backscatter Ultraviolet Radiometer (SBUV) satellite instruments. Here, we analyse 16 years (2005–2020) of ozone profile measurements from the Microwave Limb Sounder (MLS) instrument on the Aura satellite to estimate the 11-year SCS in stratospheric ozone. Our analysis of Aura-MLS data suggests a single-peak-structured SCS profile (about 3 % near 4 hPa or 40 km) in tropical stratospheric ozone, which is significantly different to the SAGE II and SBUV-based double-peak-structured SCS. We also find that MLS-observed ozone variations are more consistent with ozone from our control model simulation that uses Naval Research Laboratory (NRL) v2 solar fluxes. However, in the lowermost stratosphere modelled ozone shows a negligible SCS compared to about 1 % in Aura-MLS data. An ensemble of ordinary least squares (OLS) and three regularised (lasso, ridge and elastic net) linear regression models confirms the robustness of the estimated SCS. In addition, our analysis of MLS and model simulations shows a large SCS in the Antarctic lower stratosphere that was not seen in earlier studies. We also analyse chemical transport model simulations with alternative solar flux data. We find that in the upper (and middle) stratosphere the model simulation with Solar Radiation and Climate Experiment (SORCE) satellite solar fluxes is also consistent with the MLS-derived SCS and agrees well with the control simulation and one which uses Spectral and Total Irradiance Reconstructions (SATIRE) solar fluxes. Hence, our model simulation suggests that with recent adjustments and corrections, SORCE data can be used to analyse effects of solar flux variations. Furthermore, analysis of a simulation with fixed solar fluxes and one with fixed (annually repeating) meteorology confirms that the implicit dynamical SCS in the (re)analysis data used to force the model is not enough to simulate the observed SCS in the middle and upper stratospheric ozone. Finally, we argue that the overall significantly different SCS compared to previous estimates might be due to a combination of different factors such as much denser MLS measurements, almost linear stratospheric chlorine loading changes over the analysis period, variations in the stratospheric dynamics as well as relatively unperturbed stratospheric aerosol layer that might have influenced earlier analyses.

Impact of dust loading on ozone, winds and heating rates in the atmosphere of mars: Seasonal variability, climatology and SPICAM observations

We have used SPICAM-UV nadir observations for four Martian Years (MY27-MY30) to study the seasonal variability of column abundances of ozone and dust opacity at low latitudes (10°-30°), mid-latitudes (30°-50°) and high latitudes (50°-70°) in both hemispheres. The observed column abundances of ozone are compared with the Mars Climate Database (MCD, version 5.3) between MY27 and MY30 at these latitudes. In these observations year-to-year seasonal variability of column ozone were nearly the same except the enhancement in MY28 in the latitude range ∼10-30°S and Ls∼270°-310° when a global dust storm occurred. We have also calculated vertical profiles of O3 heating rates from the MCD model in presence of a dust storm at different latitudes and solar longitudes. At low and mid-latitudes, the ozone heating rates increase until Ls ∼47.5°. Afterwards, they decrease until Ls∼ 127.5° and then they reached a minimum value between Ls∼ 167.5° and 327.5°. In the presence of a dust storm, ozone heating rates increase by a factor of 2.5–3 up to 10 ​km at Ls∼280°. MCD results are also used to study the seasonal variability of zonal, meridional and vertical winds in the tropical atmosphere of Mars during MY28 and MY29. It is found that the density of ozone, wind speeds and ozone heating rates are severely affected by the global dust storm up to 10 ​km at latitude ∼25°S for Ls ∼270°-310°.

Rural vehicle emission as an important driver for the variations of summertime tropospheric ozone in the Beijing-Tianjin-Hebei region during 2014–2019

Tropospheric ozone (O3) pollution is increasing in the Beijing-Tianjin-Hebei (BTH) region despite a significant decline in atmospheric fine aerosol particles (PM2.5) in recent years. However, the intrinsic reason for the elevation of the regional O3 is still unclear. In this study, we analyzed the spatio-temporal variations of tropospheric O3 and relevant pollutants (PM2.5, NO2, and CO) in the BTH region based on monitoring data from the China Ministry of Ecology and Environment during the period of 2014–2019. The results showed that summertime O3 concentrations were constant in Beijing (BJ, 0.06 µg/(m3•year)) but increased significantly in Tianjin (TJ, 9.09 µg/(m3•year)) and Hebei (HB, 6.06 µg/(m3•year)). Distinct O3 trends between Beijing and other cities in BTH could not be attributed to the significant decrease in PM2.5 (from -5.08 to -6.32 µg/(m3•year)) and CO (from -0.053 to -0.090 mg/(m3•year)) because their decreasing rates were approximately the same in all the cities. The relatively stable O3 concentrations during the investigating period in BJ may be attributed to a faster decreasing rate of NO2 (BJ: -2.55 µg/(m3•year); TJ: -1.16 µg/(m3•year); HB: -1.34 µg/(m3•year)), indicating that the continued reduction of NOx will be an effective mitigation strategy for reducing regional O3 pollution. Significant positive correlations were found between daily maximum 8 hr average (MDA8) O3 concentrations and vehicle population and highway freight transportation in HB. Therefore, we speculate that the increase in rural NOx emissions due to the increase in vehicle emissions in the vast rural areas around HB greatly accelerates regional O3 formation, accounting for the significant increasing trends of O3 in HB.

Spatiotemporal Variation in Ozone and its Driving Factors: A Comparative Study of Coastal and Inland Cities in Eastern China

Spatiotemporal Variation in Ozone and its Driving Factors: A Comparative Study of Coastal and Inland Cities in Eastern China

Investigating Contributions of Total Column Ozone Variation on Some Meteorological Parameters in Nigeria

The relationship between some meteorological parameters and variation of total column ozone (TCO) concentration in Nigeria is studied from 1998-2012. The results using a descriptive analysis revealed a seasonal ozone variation having the same trend in all the stations during the period of study. High variability of TCO occurred between December and March coinciding with the period of dry season and low variability of TCO was observed in August coinciding with the period of rainy season. The observed trends in all the stations show that the TCO variation in Nigeria is mostly caused by natural occurrences. Calabar and Port Harcourt stations showed a high percent of TCO variability, while Kano and Maiduguri indicated a low percentage of TCO variability. Using Spearman correlation analysis, TCO concentration has a strong negative correlation with temperature in some stations with correlation coefficient (r) (-0.8392, -0.8531, -0.7832, -8881 and -0.7902) for Calabar, Port Harcourt, Makurdi, Lagos and Ilorin respectively. Kano and Maiduguri showed a weak positive correlation coefficient (r) 0.4965 and 0.3776 respectively. Positive correlation observed in Kano and Maiduguri could be as a result of high dehydration of water vapour in these stations due to seasonal harmattan and latitudinal effects. Probably, some of the substances that could deplete ozone such as HCl, aerosol are soluble in water thereby being washed off by rain during wet season leading to maximum TCO concentration during rainy season. Consequently, the observed phenomenon is through transportation of ozone content through the influence of Brewer-Dobson circulation. Again, during wet season, there is the mechanism of low pressure and lower tropopause height phenomenon, therefore, total ozone enhancement. Interestingly, variation in TCO is part of symbolic tools for tropospheric meteorology alteration and this invariably leads to climate change.