scholarly journals Multi-decadal surface ozone trends at globally distributed remote locations

Elem Sci Anth ◽  
2020 ◽  
Vol 8 ◽  
Author(s):  
Owen R. Cooper ◽  
Martin G. Schultz ◽  
Sabine Schröder ◽  
Kai-Lan Chang ◽  
Audrey Gaudel ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Tropospheric Ozone ◽  
Surface Ozone ◽  
Positive Trend ◽  
Remote Locations ◽  
Ozone Trends ◽  
Ozone Precursor ◽  
Globally Distributed

Extracting globally representative trend information from lower tropospheric ozone observations is extremely difficult due to the highly variable distribution and interannual variability of ozone, and the ongoing shift of ozone precursor emissions from high latitudes to low latitudes. Here we report surface ozone trends at 27 globally distributed remote locations (20 in the Northern Hemisphere, 7 in the Southern Hemisphere), focusing on continuous time series that extend from the present back to at least 1995. While these sites are only representative of less than 25% of the global surface area, this analysis provides a range of regional long-term ozone trends for the evaluation of global chemistry-climate models. Trends are based on monthly mean ozone anomalies, and all sites have at least 20 years of data, which improves the likelihood that a robust trend value is due to changes in ozone precursor emissions and/or forced climate change rather than naturally occurring climate variability. Since 1995, the Northern Hemisphere sites are nearly evenly split between positive and negative ozone trends, while 5 of 7 Southern Hemisphere sites have positive trends. Positive trends are in the range of 0.5–2 ppbv decade–1, with ozone increasing at Mauna Loa by roughly 50% since the late 1950s. Two high elevation Alpine sites, discussed by previous assessments, exhibit decreasing ozone trends in contrast to the positive trend observed by IAGOS commercial aircraft in the European lower free-troposphere. The Alpine sites frequently sample polluted European boundary layer air, especially in summer, and can only be representative of lower free tropospheric ozone if the data are carefully filtered to avoid boundary layer air. The highly variable ozone trends at these 27 surface sites are not necessarily indicative of free tropospheric trends, which have been overwhelmingly positive since the mid-1990s, as shown by recent studies of ozonesonde and aircraft observations.

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.

scholarly journals The influence of European pollution on ozone in the Near East and northern Africa

2008 ◽  
Vol 8 (1) ◽  
pp. 1913-1950 ◽  
Author(s):  
B. N. Duncan ◽  
J. J. West ◽  
Y. Yoshida ◽  
A. M. Fiore ◽  
J. R. Ziemke
Keyword(s):  
Boundary Layer ◽  
Air Quality ◽  
Near East ◽  
Surface Ozone ◽  
Northern Africa ◽  
Ozone Production ◽  
Ozone Pollution ◽  
East European ◽  
European Health ◽  
Ozone Precursor

Abstract. We present a modeling study of the long-range transport of pollution from Europe, showing that European emissions regularly elevate surface ozone by as much as 20 ppbv in summer in northern Africa and the Near East. European emissions cause 50–150 additional violations per year (i.e., above those that would occur without European pollution) of the European health standard for ozone (8-h average >120 μg/m3 or ~60 ppbv) in northern Africa and the Near East. We estimate that 19 000 additional mortalities occur annually in these regions from exposure to European ozone pollution and 50 000 additional deaths globally; the majority of the additional deaths occurs outside of Europe. Much of the pollution from Europe is exported southward at low altitudes in summer to the Mediterranean Sea, northern Africa and the Near East, regions with favorable photochemical environments for ozone production. Our results suggest that assessments of the human health benefits of reducing ozone precursor emissions in Europe should include effects outside of Europe, and that comprehensive planning to improve air quality in northern Africa and the Near East likely needs to address European emissions. We also show that the tropospheric ozone column data product derived from the OMI and MLS instruments is currently of limited value for air quality applications as the portion of the column above the boundary layer and below the tropopause is large and variable, effectively obscuring the boundary layer signal.

scholarly journals Estimation of Lower-Stratosphere-to-Troposphere Ozone Profile Using Long Short-Term Memory (LSTM)

2021 ◽  
Vol 13 (7) ◽  
pp. 1374
Author(s):  
Xinxin Zhang ◽  
Ying Zhang ◽  
Xiaoyan Lu ◽  
Lu Bai ◽  
Liangfu Chen ◽  
...  
Keyword(s):  
Air Pollution ◽  
Northern Hemisphere ◽  
Tropospheric Ozone ◽  
Lower Stratosphere ◽  
Short Term Memory ◽  
Surface Ozone ◽  
Short Term ◽  
Term Memory ◽  
Ozone Concentrations ◽  
Long Short Term Memory

Climate change and air pollution are emerging topics due to their possible enormous implications for health and social perspectives. In recent years, tropospheric ozone has been recognized as an important greenhouse gas and pollutant that is detrimental to human health, agriculture, and natural ecosystems, and has shown a trend of increasing interest. Machine-learning-based approaches have been widely applied to the estimation of tropospheric ozone concentrations, but few studies have included tropospheric ozone profiles. This study aimed to predict the Northern Hemisphere distribution of Lower-Stratosphere-to-Troposphere (LST) ozone at a pressure of 100 hPa to the near surface by employing a deep learning Long Short-Term Memory (LSTM) model. We referred to a history of all the observed parameters (meteorological data of European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5), satellite data, and the ozone profiles of the World Ozone and Ultraviolet Data Center (WOUDC)) between 2014 and 2018 for training the predictive models. Model–measurement comparisons for the monitoring sites of WOUDC for the period 2019–2020 show that the mean correlation coefficients (R2) in the Northern Hemisphere at high latitude (NH), Northern Hemisphere at middle latitude (NM), and Northern Hemisphere at low latitude (NL) are 0.928, 0.885, and 0.590, respectively, indicating reasonable performance for the LSTM forecasting model. To improve the performance of the model, we applied the LSTM migration models to the Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrument Container (CARIBIC) flights in the Northern Hemisphere from 2018 to 2019 and three urban agglomerations (the Sichuan Basin (SCB), North China Plain (NCP), and Yangtze River Delta region (YRD)) between 2018 and 2019. The results show that our models performed well on the CARIBIC data set, with a high R2 equal to 0.754. The daily and monthly surface ozone concentrations for 2018–2019 in the three urban agglomerations were estimated from meteorological and ancillary variables. Our results suggest that the LSTM models can accurately estimate the monthly surface ozone concentrations in the three clusters, with relatively high coefficients of 0.815–0.889, root mean square errors (RMSEs) of 7.769–8.729 ppb, and mean absolute errors (MAEs) of 6.111–6.930 ppb. The daily scale performance was not as high as the monthly scale performance, with the accuracy of R2 = 0.636~0.737, RMSE = 14.543–16.916 ppb, MAE = 11.130–12.687 ppb. In general, the trained module based on LSTM is robust and can capture the variation of the atmospheric ozone distribution. Moreover, it also contributes to our understanding of the mechanism of air pollution, especially increasing our comprehension of pollutant areas.

scholarly journals Dynamic changes of terrestrial net primary production and its feedback to evapotranspiration

2016 ◽  
Author(s):  
Zhi Li ◽  
Yaning Chen ◽  
Yang Wang ◽  
Gonghuan Fang
Keyword(s):  
Primary Production ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Environmental Changes ◽  
Water Cycle ◽  
Net Primary Production ◽  
Positive Trend ◽  
Precipitation Trend ◽  
Vegetation Productivity ◽  
Increased Risk

Abstract. Earth experienced dramatic environmental changes in the recent 15 years (2000–2014). The past decade has been the warmest in the instrumental record, which significantly influences the global water cycle and vegetation activities. Overall, the global inter-annual series of net primary production (NPP) slightly increased in 2000–2014 at a rate of 0.06 PgC/yr2. More than 64 % of vegetated land in the Northern Hemisphere showed increased net primary production, while 60.3 % of vegetated land in the Southern Hemisphere showed decreased trend. Net primary production correlates positively with land actual evapotranspiration (ET), especially in the Northern Hemisphere, where the increased vegetation productivity (0.13 PgC/yr2) promotes decadal rises of terrestrial evapotranspiration (0.61 mm/yr2). However, anomalous dry conditions led to reduced vegetation productivity (−0.18 PgC/yr2) and nearly ceased growth in terrestrial evapotranspiration in the Southern Hemisphere (0.41 mm/yr2). Under the content of past warmest 15 years, global potential evapotranspiration (PET) shows an increasing trend of 1.72 mm/yr2, while precipitation for the domain shows a variability positive trend of 0.84 mm/yr2, which consistent with expected water cycle intensification. But precipitation trend is lower than evaporative demand, indicating some moisture deficit between available water demand and supply for evapotranspiration, thereby accelerated soil moisture loss. Drought indices and precipitation-minus-evaporation suggested an increased risk of drought in the present century. To understand why climates in the northern and southern hemispheres respond differently to NPP, the results showed that temperature is the dominant control on vegetation growth in the high latitude in the Northern Hemisphere, while net radiation is the main effect factors to NPP in the mid latitude, and in arid and semi-arid biomes also mainly driven by precipitation. While in the Southern Hemisphere, NPP decreased because of warming associated drying trends of PDSI.

scholarly journals Can we explain the trends in European ozone levels?

2005 ◽  
Vol 5 (4) ◽  
pp. 5957-5985 ◽  
Author(s):  
J. E. Jonson ◽  
D. Simpson ◽  
H. Fagerli ◽  
S. Solberg
Keyword(s):  
North Atlantic ◽  
Polar Region ◽  
Surface Ozone ◽  
Lateral Boundary ◽  
Model Calculations ◽  
The North ◽  
Ozone Trends ◽  
Ozone Precursor ◽  
Ozone Episodes ◽  
Ozone Levels

Abstract. Ozone levels in Europe are changing. Emissions of ozone precursors from Europe (NOx, CO and non-methane hydrocarbons) have been substantially reduced over the last 10–15 years, but changes in ozone levels can not be explained by changes in European emissions alone. In order to explain the European trends in ozone since 1990 the EMEP regional photochemistry model has been run for the the years 1990 and 1995–2002. The EMEP model is a regional model centered over Europe but the model domain also includes most of the North Atlantic and the polar region. Climatological ozone data are used as initial and lateral boundary concentrations. Model results are compared to measurements over this timespan of 12 years. Possible causes for the measured trends in European surface ozone have been investigated using model sensitivity runs perturbing emissions and lateral boundary concentrations. The observed ozone trends at many European sites are only partially reproduced by global or regional photochemistry models, and possible reasons for this are discussed. The increase in winter ozone partially and the decrease in the magnitude of high ozone episodes is attributed to the decrease in ozone precursor emissions since 1990 by the model. Furthermore, the model calculations indicate that the emission reductions has resulted in a marked decrease in summer ozone in major parts of Europe, and in particular in Germany. Such a trend in summer ozone is likely to be difficult to identify from the measurements because of large inter-annual variability.

scholarly journals Surface and tropospheric ozone trends in the Southern Hemisphere since 1990: possible linkages to poleward expansion of the Hadley circulation

2019 ◽  
Vol 64 (6) ◽  
pp. 400-409 ◽  
Author(s):  
Xiao Lu ◽  
Lin Zhang ◽  
Yuanhong Zhao ◽  
Daniel J. Jacob ◽  
Yongyun Hu ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Tropospheric Ozone ◽  
Hadley Circulation ◽  
Ozone Trends ◽  
Poleward Expansion

scholarly journals Can we explain the trends in European ozone levels?

2006 ◽  
Vol 6 (1) ◽  
pp. 51-66 ◽  
Author(s):  
J. E. Jonson ◽  
D. Simpson ◽  
H. Fagerli ◽  
S. Solberg
Keyword(s):  
North Atlantic ◽  
Polar Region ◽  
Surface Ozone ◽  
Lateral Boundary ◽  
Model Calculations ◽  
The North ◽  
Ozone Trends ◽  
Ozone Precursor ◽  
Ozone Episodes ◽  
Ozone Levels

Abstract. Ozone levels in Europe are changing. Emissions of ozone precursors from Europe (NOx, CO and non-methane hydrocarbons) have been substantially reduced over the last 10–15 years, but changes in ozone levels cannot be explained by changes in European emissions alone. The observed ozone trends at many European sites are only partially reproduced by global or regional photochemistry models, and possible reasons for this are discussed. In order to further explain the European trends in ozone since 1990, the EMEP regional photochemistry model has been run for the years 1990 and 1995–2002. The EMEP model is a regional model centred over Europe but the model domain also includes most of the North Atlantic and the polar region. Climatological ozone data are used as initial and lateral boundary concentrations. Model results are compared to measurements over this timespan of 12 years. Possible causes for the measured trends in European surface ozone have been investigated using model sensitivity runs perturbing emissions and lateral boundary concentrations. The increase in winter ozone partially, and the decrease in the magnitude of high ozone episodes, is attributed to the decrease in ozone precursor emissions since 1990 by the model. Furthermore, the model calculations indicate that the emission reductions have resulted in a marked decrease in summer ozone in major parts of Europe, in particular in Germany. Such a trend in summer ozone is likely to be difficult to identify from the measurements alone because of large inter-annual variability.

scholarly journals Aircraft observations since the 1990s reveal increases of tropospheric ozone at multiple locations across the Northern Hemisphere

2020 ◽  
Vol 6 (34) ◽  
pp. eaba8272 ◽  
Author(s):  
Audrey Gaudel ◽  
Owen R. Cooper ◽  
Kai-Lan Chang ◽  
Ilann Bourgeois ◽  
Jerry R. Ziemke ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Temporal Variability ◽  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Monitoring Network ◽  
Spatial And Temporal Variability ◽  
Commercial Aircraft ◽  
Aircraft Observations ◽  
Ozone Precursor ◽  
Satellite Product

Tropospheric ozone is an important greenhouse gas, is detrimental to human health and crop and ecosystem productivity, and controls the oxidizing capacity of the troposphere. Because of its high spatial and temporal variability and limited observations, quantifying net tropospheric ozone changes across the Northern Hemisphere on time scales of two decades had not been possible. Here, we show, using newly available observations from an extensive commercial aircraft monitoring network, that tropospheric ozone has increased above 11 regions of the Northern Hemisphere since the mid-1990s, consistent with the OMI/MLS satellite product. The net result of shifting anthropogenic ozone precursor emissions has led to an increase of ozone and its radiative forcing above all 11 study regions of the Northern Hemisphere, despite NOx emission reductions at midlatitudes.

scholarly journals Surface ozone in the southern hemisphere: 20 years of data from a site with a unique setting in El Tololo, Chile

2016 ◽  
Author(s):  
Julien G. Anet ◽  
Martin Steinbacher ◽  
Laura Gallardo ◽  
Patricio A. Velásquez Álvarez ◽  
Lukas Emmenegger ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
El Niño ◽  
El Nino ◽  
Surface Ozone ◽  
La Niña ◽  
Positive Trend ◽  
Temporal Shift ◽  
Background Ozone ◽  
La Nina ◽  
The Impact

Abstract. The knowledge of surface ozone mole fractions and their global distribution is of utmost importance due to the impact of ozone on human health and ecosystems, and the central role of ozone in controlling the oxidation capacity of the troposphere. The availability of long-term ozone records is far better in the northern than in the southern hemisphere, and recent analyses of the seven accessible records in the southern hemisphere have shown inconclusive trends. Since late 1995, surface ozone is measured in-situ at "El Tololo", a high-altitude (2200 m asl) and pristine station in Chile (30° S, 71° W). The dataset has been recently fully quality-controlled and reprocessed. This study presents the observed ozone trends and annual cycles and identifies key processes driving these patterns. From 1995 to 2010, an overall positive trend of ~ 0.7 ppb/decade is found. Strongest trends per season are observed in March and April. Highest mole fractions are observed in late spring (October) and show a strong correlation with ozone transported from the stratosphere down into the troposphere, as simulated with a model. Over the 20 years of observations, the springtime ozone maximum has shifted to earlier times in the year which, again, is strongly correlated with a temporal shift in the occurrence of the maximum of simulated stratospheric ozone transport at the site. We conclude that background ozone at El Tololo is mainly driven by stratospheric intrusions rather than photochemical production from anthropogenic and biogenic precursors. The major footprint of the sampled air masses is located over the Pacific Ocean. Therefore, due to the negligible influence of local processes, the ozone record also allows studying the influence of El Niño and La Niña episodes on background ozone levels in South America. In agreement with previous studies, we find that during La Niña conditions, ozone mole fractions reach higher levels than during El Niño conditions.

scholarly journals A global climatology of tropospheric and stratospheric ozone derived from Aura OMI and MLS measurements

2011 ◽  
Vol 11 (6) ◽  
pp. 17879-17911 ◽  
Author(s):  
J. R. Ziemke ◽  
S. Chandra ◽  
G. Labow ◽  
P. K. Bhartia ◽  
L. Froidevaux ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Tropospheric Ozone ◽  
Stratospheric Ozone ◽  
Ozone Monitoring Instrument ◽  
Mean Values ◽  
Latitude Range ◽  
The Pacific ◽  
The Pacific Ocean

Abstract. A global climatology of tropospheric and stratospheric column ozone is derived by combining six years of Aura Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) ozone measurements for the period October 2004 through December 2010. The OMI/MLS tropospheric ozone climatology exhibits large temporal and spatial variability which includes ozone accumulation zones in the tropical south Atlantic year-round and in the subtropical Mediterranean/Asia region in summer months. High levels of tropospheric ozone in the Northern Hemisphere also persist in mid-latitudes over the Eastern North American and Asian continents extending eastward over the Pacific Ocean. For stratospheric ozone climatology from MLS, largest ozone abundance lies in the Northern Hemisphere in the latitude range 70° N–80° N in February–April and in the Southern Hemisphere around 40° S–50° S during months August–October. The largest stratospheric ozone abundances in the Northern Hemisphere lie over North America and Eastern Asia extending eastward across the Pacific Ocean and in the Southern Hemisphere south of Australia extending eastward across the dateline. With the advent of many newly developing 3-D chemistry and transport models it is advantageous to have such a dataset for evaluating the performance of the models in relation to dynamical and photochemical processes controlling the ozone distributions in the troposphere and stratosphere. The OMI/MLS ozone gridded climatology data, both calculated mean values and RMS uncertainties are made available to the science community via the NASA total ozone mapping spectrometer (TOMS) website http://toms.gsfc.nasa.gov.

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