scholarly journals Surface ozone at the Caucasian site Kislovodsk High Mountain Station and the Swiss Alpine site Jungfraujoch: data analysis and trends (1990–2006)

2009 ◽  
Vol 9 (12) ◽  
pp. 4157-4175 ◽  
Author(s):  
O. A. Tarasova ◽  
I. A. Senik ◽  
M. G. Sosonkin ◽  
J. Cui ◽  
J. Staehelin ◽  
...  
Keyword(s):  
Western Europe ◽  
Surface Ozone ◽  
Lower Troposphere ◽  
High Mountain ◽  
Free Troposphere ◽  
Mixing Ratios ◽  
Mountain Station ◽  
Ozone Trends ◽  
Transport Patterns ◽  
In The Beginning

Abstract. Long-term ozone measurements of two background mountain sites, namely the Kislovodsk High Mountain Station in Caucasus, Russia (KHMS, 43.70° N, 42.70° E, 2070 m a.s.l.) and the Jungfraujoch in Switzerland (JFJ, 46.55° N, 7.98° E, 3580 m a.s.l.) are compared. Despite of more than 1.5 km altitude difference ozone mixing ratios are comparable at JFJ an KHMS in the beginning of measurements (1990–1993) while the annually averaged levels at JFJ are around 15 ppb higher than the ones at KHMS for the most recent years (1997–2006). The seasonal cycle of the surface ozone mixing ratios is characterized by a double spring-summer maximum at both sites with a spring one being more pronounced for the air masses with the longest contact with the upper free troposphere and stratosphere. Ozone mixing ratio increased at JFJ but decreased at KHMS for the period 1990–2006. Trends are more pronounced for the 1990s (+0.73±0.20 ppb/year at JFJ and −0.91±0.17 ppb/year at KHMS for the period 1991–2001) in comparison with the later years (+0.04±0.21 ppb/year at JFJ and −0.37±0.14 ppb/year at KHMS for the period 1997–2006). Trends show a distinct seasonality, which is different for the different periods. To investigate possible reasons for this remarkable trends difference 3-D trajectories using LAGRANTO trajectory model are used. Effects of horizontal and vertical transport on ozone trends are considered. No substantial systematic changes in the transport patterns were detected which could lead to strong changes in the trend magnitude between 1991–2001 and 1997–2006. The geographical position of the sites relative to the main topographic features and emission sources as well as distance from the coast are interpreted to be among the main reasons for the opposite surface ozone trends. During the 90s the JFJ trend reflects increase of the ozone in the upper free troposphere/lower stratosphere, while KHMS is not sensitive to this change or even showing the opposite tendency. The analysis provided evidence for a stronger influence of processes in the lower troposphere, in particular the dramatic emission decrease in the earlier 1990s in former USSR and emissions regulations in Western Europe on the surface ozone trend at KHMS.

scholarly journals Surface ozone at the Caucasian site Kislovodsk High Mountain Station and the Swiss Alpine site Jungfraujoch: data analysis and trends (1990–2006)

2009 ◽  
Vol 9 (1) ◽  
pp. 905-954
Author(s):  
O. A. Tarasova ◽  
I. A. Senik ◽  
M. G. Sosonkin ◽  
J. Cui ◽  
J. Staehelin ◽  
...  
Keyword(s):  
Western Europe ◽  
Surface Ozone ◽  
High Mountain ◽  
Free Troposphere ◽  
Ozone Concentrations ◽  
Mountain Station ◽  
Ozone Trends ◽  
Summer Maximum ◽  
Transport Patterns ◽  
In The Beginning

Abstract. Long-term ozone measurements of two background mountain sites, namely the Kislovodsk High Mountain Station in Caucasus, Russia (KHMS, 43.70° N, 42.70° E, 2070 m a.s.l.) and the Jungfraujoch in Switzerland (JFJ, 46.55° N, 7.98° E, 3580 m a.s.l.) are compared. Despite of more than 1.5 km altitude difference ozone concentrations are comparable at JFJ an KHMS in the beginning of measurements (1990–1993) while the annually averaged levels at JFJ are around 15 ppb higher than the ones at KHMS for the most recent years (1997–2006). Averaged for different periods ozone concentrations at KHMS are comparable with the respective values observed at the elevated sites in the midlatitudes, situated in the altitude range 1600–2400 m a.s.l. Distribution function of the hourly concentrations has two peaks at JFJ and it is close to Gaussian distribution in the case of KHMS. Seasonality at both sites is characterized by double spring-summer maximum. Spring maximum at both stations is more pronounced for the air masses with the longest contact with upper free troposphere and stratosphere. Average concentrations increased at JFJ but decreased at KHMS for the period 1990–2006. Trends are more pronounced for the 1990s (+0.73±0.20 ppb/year at JFJ and −0.91±0.17 ppb/year at KHMS for the period 1991–2001) in comparison with later years (+0.04±0.21 ppb/year at JFJ and −0.37±0.14 ppb/year at KHMS for the period 1997–2006). Trends show a distinct seasonality, which is different for the different periods. To investigate possible reasons for this remarkable trends difference 3-D trajectories using LAGRANTO trajectory model are used. Effects of the horizontal and vertical transport on ozone trends are considered. In general we could not find any systematic changes in the transport patterns which could explain the significant changes of the trends between 1991–2001 and 1997–2006. It is likely that the position of the main emission source areas relative to the stations is among the main reason for the opposite surface ozone trends. During the 1990s the JFJ trend reflects increase of the ozone in the upper free troposphere/lower stratosphere. In contrary KHSM is much more influenced by dramatic emission decrease in the earlier 1990s in former USSR and emissions regulations in Western Europe. For later years ozone trends at KHMS are controlled by slight emission increase in the region, while trends at JFJ correspond to the scenario of European emissions control.

scholarly journals Impacts of different characterizations of large-scale background on simulated regional-scale ozone over the continental United States

2018 ◽  
Vol 18 (5) ◽  
pp. 3839-3864 ◽  
Author(s):  
Christian Hogrefe ◽  
Peng Liu ◽  
George Pouliot ◽  
Rohit Mathur ◽  
Shawn Roselle ◽  
...  
Keyword(s):  
Air Quality ◽  
Boundary Conditions ◽  
Large Scale ◽  
Surface Ozone ◽  
Regional Scale ◽  
Model Performance ◽  
Lower Troposphere ◽  
Substantial Impact ◽  
Mixing Ratios ◽  
Scale Models

Abstract. This study analyzes simulated regional-scale ozone burdens both near the surface and aloft, estimates process contributions to these burdens, and calculates the sensitivity of the simulated regional-scale ozone burden to several key model inputs with a particular emphasis on boundary conditions derived from hemispheric or global-scale models. The Community Multiscale Air Quality (CMAQ) model simulations supporting this analysis were performed over the continental US for the year 2010 within the context of the Air Quality Model Evaluation International Initiative (AQMEII) and Task Force on Hemispheric Transport of Air Pollution (TF-HTAP) activities. CMAQ process analysis (PA) results highlight the dominant role of horizontal and vertical advection on the ozone burden in the mid-to-upper troposphere and lower stratosphere. Vertical mixing, including mixing by convective clouds, couples fluctuations in free-tropospheric ozone to ozone in lower layers. Hypothetical bounding scenarios were performed to quantify the effects of emissions, boundary conditions, and ozone dry deposition on the simulated ozone burden. Analysis of these simulations confirms that the characterization of ozone outside the regional-scale modeling domain can have a profound impact on simulated regional-scale ozone. This was further investigated by using data from four hemispheric or global modeling systems (Chemistry – Integrated Forecasting Model (C-IFS), CMAQ extended for hemispheric applications (H-CMAQ), the Goddard Earth Observing System model coupled to chemistry (GEOS-Chem), and AM3) to derive alternate boundary conditions for the regional-scale CMAQ simulations. The regional-scale CMAQ simulations using these four different boundary conditions showed that the largest ozone abundance in the upper layers was simulated when using boundary conditions from GEOS-Chem, followed by the simulations using C-IFS, AM3, and H-CMAQ boundary conditions, consistent with the analysis of the ozone fields from the global models along the CMAQ boundaries. Using boundary conditions from AM3 yielded higher springtime ozone columns burdens in the middle and lower troposphere compared to boundary conditions from the other models. For surface ozone, the differences between the AM3-driven CMAQ simulations and the CMAQ simulations driven by other large-scale models are especially pronounced during spring and winter where they can reach more than 10 ppb for seasonal mean ozone mixing ratios and as much as 15 ppb for domain-averaged daily maximum 8 h average ozone on individual days. In contrast, the differences between the C-IFS-, GEOS-Chem-, and H-CMAQ-driven regional-scale CMAQ simulations are typically smaller. Comparing simulated surface ozone mixing ratios to observations and computing seasonal and regional model performance statistics revealed that boundary conditions can have a substantial impact on model performance. Further analysis showed that boundary conditions can affect model performance across the entire range of the observed distribution, although the impacts tend to be lower during summer and for the very highest observed percentiles. The results are discussed in the context of future model development and analysis opportunities.

scholarly journals Influence of altitude on ozone levels and variability in the lower troposphere: a ground-based study for western Europe over the period 2001–2004

2007 ◽  
Vol 7 (1) ◽  
pp. 1327-1356 ◽  
Author(s):  
A. Chevalier ◽  
F. Gheusi ◽  
R. Delmas ◽  
C. Ordó\\ nez ◽  
C. Sarrat ◽  
...  
Keyword(s):  
Western Europe ◽  
Lower Troposphere ◽  
Monitoring And Evaluation ◽  
Weather Conditions ◽  
High Elevation ◽  
Global Scale ◽  
Observation System ◽  
Mountainous Areas ◽  
Mixing Ratios ◽  
Spring Maximum

Abstract. The PAES (French acronym for synoptic scale atmospheric pollution) network focuses on the chemical composition (ozone, CO, NOx/y and aerosols) of the lower troposphere (0–3000 m). Its high-altitude surface stations located in different mountainous areas in France complete the low-altitude rural MERA stations (the French contribution to the european program EMEP, European Monitoring and Evaluation Program). They are representative of pollution at the scale of the French territory because they are away from any major source of pollution. This study deals with ozone observations between 2001 and 2004 at 11 stations from PAES and MERA, in addition to 16 elevated stations located in mountainous areas of Switzerland, Germany, Austria, Italy and Spain. The set of stations covers a range of altitudes between 115 and 3550 m. The comparison between recent ozone mixing ratios with those of the last decade found in the literature for two high-elevation sites (Pic du Midi, 2877 m and Jungfraujoch, 3580 m) leads to a trend that has slowed down compared to old trends but remains positive. This could be attribuable to the reduction of ozone precursors at European scale, that however do not compensate an ozone increase at the global scale. Averaged levels of ozone increase with elevation in good agreement with data provided by the airborne observation system MOZAIC (Measurement of OZone and water vapour by Airbus In-service airCraft), showing a highly stratified ozone field in the lower troposphere, with a transition at about 1000 m asl between a sharp gradient (30 ppb/km) below but a gentler gradient (3 ppb/km) above. Ozone variability also reveals a clear transition between boundary-layer and free-tropospheric regimes at the same altitude. Below, diurnal photochemistry accounts for about the third of the variability in summer, but less than 20% above – and at all levels in winter – where ozone variability is mostly due to day-to-day changes (linked to weather conditions or synoptic transport). Monthly-mean ozone mixing-ratios show at all levels a minimum in winter and the classical summer broad maximum in spring and summer – which is actually the superposition of the tropospheric spring maximum (April–May) and regional pollution episodes linked to persistent anticyclonic conditions that may occur from June to September. To complement this classical result it is shown that summer maxima are associated with considerably more variability than the spring maximum. This ensemble of findings support the relevance of mountain station networks such as PAES for the long-term observation of free-tropospheric ozone over Europe.

scholarly journals Impacts of Different Characterizations of Large-Scale Background on Simulated Regional-Scale Ozone Over the Continental United States

2017 ◽  
Author(s):  
Christian Hogrefe ◽  
Peng Liu ◽  
George Pouliot ◽  
Rohit Mathur ◽  
Shawn Roselle ◽  
...  
Keyword(s):  
Air Quality ◽  
Boundary Conditions ◽  
Large Scale ◽  
Surface Ozone ◽  
Regional Scale ◽  
Model Performance ◽  
Lower Troposphere ◽  
Substantial Impact ◽  
Mixing Ratios ◽  
Scale Models

Abstract. This study analyzes simulated regional-scale ozone burdens both near the surface and aloft, estimates process contributions to these burdens, and calculates the sensitivity of the simulated regional-scale ozone burden to several key model inputs with a particular emphasis on boundary conditions derived from hemispheric or global scale models. The Community Multiscale Air Quality (CMAQ) model simulations supporting this analysis were performed over the continental U.S. for the year 2010 within the context of the Air Quality Model Evaluation International Initiative (AQMEII) and Task Force on Hemispheric Transport of Air Pollution (TF-HTAP) activities. CMAQ Process Analysis (PA) results highlight the dominant role of horizontal and vertical advection on the ozone burden in the mid-to-upper troposphere and lower stratosphere. Vertical mixing, including mixing by convective clouds, couple fluctuations in free tropospheric ozone to ozone in lower layers. Hypothetical bounding scenarios were performed to quantify the effects of emissions, boundary conditions, and ozone dry deposition on the simulated ozone burden. Analysis of these simulations confirms that the characterization of ozone outside the regional-scale modeling domain can have a profound impact on simulated regional-scale ozone. This was further investigated by using data from four hemispheric or global modeling systems (Chemistry – Integrated Forecasting Model (C-IFS), CMAQ extended for hemispheric applications (H-CMAQ), GEOS-Chem, and AM3) to derive alternate boundary conditions for the regional-scale CMAQ simulations. The regional-scale CMAQ simulations using these four different boundary conditions showed that the largest ozone abundance in the upper layers was simulated when using boundary conditions from GEOS-Chem, followed by the simulations using C-IFS, AM3, and H-CMAQ boundary conditions, consistent with the analysis of the ozone fields from the global models along the CMAQ boundaries. Using boundary conditions from AM3 yielded higher springtime ozone columns burdens in the mid- and lower troposphere compared to boundary conditions from the other models. For surface ozone, the differences between the AM3-driven CMAQ simulations and the CMAQ simulations driven by other large-scale models are especially pronounced during spring and winter where they can reach more than 10 ppb for seasonal mean ozone mixing ratios and as much as 15 ppb for domain-averaged daily maximum 8-hr average ozone on individual days. In contrast, the differences between the C-IFS, GEOS-Chem, and H-CMAQ driven regional-scale CMAQ simulations are typically smaller. Comparing simulated surface ozone mixing ratios to observations and computing seasonal and regional model performance statistics revealed that boundary conditions can have a substantial impact on model performance. Further analysis showed that boundary conditions can affect model performance across the entire range of the observed distribution, although the impacts tend to be lower during summer and for the very highest observed percentiles. The results are discussed in the context of future model development and analysis opportunities.

scholarly journals Long-path averaged mixing ratios of O<sub>3</sub> and NO<sub>2</sub> in the free troposphere from mountain MAX-DOAS

2013 ◽  
Vol 6 (5) ◽  
pp. 8235-8267
Author(s):  
L. Gomez ◽  
M. Navarro-Comas ◽  
O. Puentedura ◽  
Y. Gonzalez ◽  
E. Cuevas ◽  
...  
Keyword(s):  
Detection Limit ◽  
Optical Absorption ◽  
Radiative Transfer Model ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
High Mountain ◽  
Free Troposphere ◽  
Air Masses ◽  
Mixing Ratios

Abstract. A new approximation is proposed to estimate O3 and NO2 mixing ratios in the Northern Subtropics Free Troposphere (FT). Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) high mountain measurements, recorded at Izaña Observatory (28°18' N, 16°29' W), are used in this work. Proposed method uses horizontal and near-zenith geometries to estimate the station level differential path. Two different methods are described. First one uses retrieved Slant Column Densities (SCD) of O4. On second method, path is estimated from LIBRADTRAN radiative transfer model for the region and season. Results show that under low aerosol loading, O3 and NO2 mixing ratios concentrations can be retrieved with moderately low errors. Obtained concentrations have been compared with in situ instrumentation on the observatory. O3 concentration in FT is found to be in the range of 40–80 ppb, approximately. NO2 is in the range of 20–30 ppt, below the detection limit of in situ instrumentation. The different air masses scanned by each instrument have been identified as a cause of discrepancy between O3 observed by MAX-DOAS and in situ.

scholarly journals Chemical characteristics assigned to trajectory clusters during the MINOS campaign

2003 ◽  
Vol 3 (2) ◽  
pp. 459-468 ◽  
Author(s):  
M. Traub ◽  
H. Fischer ◽  
M. de Reus ◽  
R. Kormann ◽  
H. Heland ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
South Asia ◽  
North Atlantic ◽  
Western Europe ◽  
North Atlantic Ocean ◽  
Lower Troposphere ◽  
Back Trajectories ◽  
Air Masses ◽  
Upper Troposphere ◽  
Mixing Ratios

Abstract. During the Mediterranean Intensive Oxidant Study (MINOS) in August 2001 a total of 14 measurement flights were performed with the DLR Falcon jet aircraft from Heraklion, Crete. One objective of this campaign was to investigate the role of long-range transport of pollutants into the Mediterranean area. An analysis of 5-day back trajectories indicates that in the lower troposphere (0-4 km) air masses originated from eastern and western Europe, in the mid-troposphere (4-8 km) from the North Atlantic Ocean region and in the upper troposphere (8-14 km) from North Atlantic Ocean/North America (NANA) as well as South Asia. We allocated all back trajectories to clusters based on their ending height and source region. The mixing ratios of ozone, nitrogen oxide, total reactive oxidized nitrogen (NOy), formaldehyde, methanol, acetonitrile, acetone, peroxyacetyl nitrate (PAN), carbon dioxide, carbon monoxide and methane measured along the flight tracks are examined in relation to the different cluster trajectories. In the lower troposphere the mean trace gas mixing ratios of the eastern Europe cluster trajectories were significantly higher than those from western Europe. In the upper troposphere air from the NANA region seems to be influenced by the stratosphere, in addition, air masses were transported from South Asia, being influenced by strong convection in the Indian monsoon.

scholarly journals Chemical characteristics assigned to trajectory clusters during the MINOS campaign

2003 ◽  
Vol 3 (1) ◽  
pp. 107-134 ◽  
Author(s):  
M. Traub ◽  
H. Fischer ◽  
M. de Reus ◽  
R. Kormann ◽  
J. Heland ◽  
...  
Keyword(s):  
Western Europe ◽  
Source Region ◽  
Lower Troposphere ◽  
Mediterranean Area ◽  
Back Trajectories ◽  
Air Masses ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
The Mediterranean ◽  
High Concentrations

Abstract. During the Mediterranean Intensive Oxidant Study (MINOS) in August 2001 a total of 14 measurement flights were performed with the DLR Falcon aircraft from Heraklion, Crete. One objective of this campaign was to investigate the role of long-range transport of pollutants into the Mediterranean area. An analysis of 5-day back trajectories indicates that in the lower troposphere (0–4 km) air masses originated from eastern and western Europe, in the mid-troposphere (4–8 km) from the Atlantic Ocean region and in the upper troposphere (8–14 km) from North Artlantic Ocean/North America  (NAONA) as well as South Asia. We allocated all back trajectories to clusters based on their ending height and source region. The mixing ratios of ozone, nitrogen oxide, total reactive oxidized nitrogen (NOy), formaldehyde, methanol, acetonitrile, acetone, peroxyacetyl nitrate (PAN), carbon dioxide, carbon monoxide and methane measured along the flight tracks are examined in relation to the different cluster trajectories. In the lower troposphere the mean gas mixing ratios of the eastern Europe cluster trajectories were significantly higher than that from western Europe. Considering 2-day instead of 5-day trajectories the relative differences between the concentrations of these two clusters increased. In the upper troposphere relatively high concentrations of  O3 and NOy, combined with low CO of the NAONA trajectories indicate mixing with stratospheric air masses.

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

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

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

scholarly journals Long-path averaged mixing ratios of O<sub>3</sub> and NO<sub>2</sub> in the free troposphere from mountain MAX-DOAS

2014 ◽  
Vol 7 (10) ◽  
pp. 3373-3386 ◽  
Author(s):  
L. Gomez ◽  
M. Navarro-Comas ◽  
O. Puentedura ◽  
Y. Gonzalez ◽  
E. Cuevas ◽  
...  
Keyword(s):  
Optical Absorption Spectroscopy ◽  
High Mountain ◽  
Geometrical Approach ◽  
Free Troposphere ◽  
Simple Method ◽  
Air Masses ◽  
Mixing Ratios ◽  
Horizontal Path ◽  
Low Concentrations

Abstract. A new approximation is proposed to estimate O3 and NO2 mixing ratios in the northern subtropical free troposphere (FT). The proposed method uses O4 slant column densities (SCDs) at horizontal and near-zenith geometries to estimate a station-level differential path. The modified geometrical approach (MGA) is a simple method that takes advantage of a very long horizontal path to retrieve mixing ratios in the range of a few pptv. The methodology is presented, and the possible limitations are discussed. Multi-axis differential optical absorption spectroscopy (MAX-DOAS) high-mountain measurements recorded at the Izaña observatory (28° 18' N, 16° 29' W) are used in this study. The results show that under low aerosol loading, O3 and NO2 mixing ratios can be retrieved even at very low concentrations. The obtained mixing ratios are compared with those provided by in situ instrumentation at the observatory. The MGA reproduces the O3 mixing ratio measured by the in situ instrumentation with a difference of 28%. The different air masses scanned by each instrument are identified as a cause of the discrepancy between the O3 observed by MAX-DOAS and the in situ measurements. The NO2 is in the range of 20–40 ppt, which is below the detection limit of the in situ instrumentation, but it is in agreement with measurements from previous studies for similar conditions.

scholarly journals Global distribution and trends of tropospheric ozone: An observation-based review

Elem Sci Anth ◽  
2014 ◽  
Vol 2 ◽  
Author(s):  
O. R. Cooper ◽  
D. D. Parrish ◽  
J. Ziemke ◽  
N. V. Balashov ◽  
M. Cupeiro ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Climate Models ◽  
Surface Ozone ◽  
Air Pollutant ◽  
Global Distribution ◽  
Anthropogenic Sources ◽  
Mixing Ratios ◽  
Ozone Trends ◽  
Ozone Precursor

Abstract Tropospheric ozone plays a major role in Earth’s atmospheric chemistry processes and also acts as an air pollutant and greenhouse gas. Due to its short lifetime, and dependence on sunlight and precursor emissions from natural and anthropogenic sources, tropospheric ozone’s abundance is highly variable in space and time on seasonal, interannual and decadal time-scales. Recent, and sometimes rapid, changes in observed ozone mixing ratios and ozone precursor emissions inspired us to produce this up-to-date overview of tropospheric ozone’s global distribution and trends. Much of the text is a synthesis of in situ and remotely sensed ozone observations reported in the peer-reviewed literature, but we also include some new and extended analyses using well-known and referenced datasets to draw connections between ozone trends and distributions in different regions of the world. In addition, we provide a brief evaluation of the accuracy of rural or remote surface ozone trends calculated by three state-of-the-science chemistry-climate models, the tools used by scientists to fill the gaps in our knowledge of global tropospheric ozone distribution and trends.

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