Long-term Tropospheric Ozone Trends: A Critical Review

2008 ◽  
pp. 271-282 ◽  
Author(s):  
J. Staehelin ◽  
C. Schnadt Poberaj ◽  
J. Staehelin ◽  
C. Schnadt Poberaj
Keyword(s):  
Critical Review ◽  
Tropospheric Ozone ◽  
Ozone Trends

scholarly journals An exploration of ozone changes and their radiative forcing prior to the chlorofluorocarbon era

2002 ◽  
Vol 2 (5) ◽  
pp. 363-374 ◽  
Author(s):  
D. T. Shindell ◽  
G. Faluvegi
Keyword(s):  
Ozone Depletion ◽  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Stratospheric Ozone ◽  
Data Sets ◽  
Independent Data ◽  
Spatial Coverage ◽  
Ozone Trends ◽  
Ozone Trend

Abstract. Using historical observations and model simulations, we investigate ozone trends prior to the mid-1970s onset of halogen-induced ozone depletion. Though measurements are quite limited, an analysis based on multiple, independent data sets (direct and indirect) provides better constraints than any individual set of observations. We find that three data sets support an apparent long-term stratospheric ozone trend of -7.2 ± 2.3 DU during 1957-1975, which modeling attributes primarily to water vapor increases. The results suggest that 20th century stratospheric ozone depletion may have been roughly 50% more than is generally supposed. Similarly, three data sets support tropospheric ozone increases over polluted Northern Hemisphere continental regions of 8.2 ± 2.1 DU during this period, which are mutually consistent with the stratospheric trends. As with paleoclimate data, which is also based on indirect proxies and/or limited spatial coverage, these results must be interpreted with caution. However, they provide the most thorough estimates presently available of ozone changes prior to the coincident onset of satellite data and halogen dominated ozone changes. If these apparent trends were real, the radiative forcing by stratospheric ozone since the 1950s would then have been -0.15 ± 0.05 W/m2, and -0.2 W/m2 since the preindustrial. For tropospheric ozone, it would have been 0.38 ± 0.10 W/m2 since the late 1950s. Combined with even a very conservative estimate of tropospheric ozone forcing prior to that time, this would be larger than current estimates since 1850 which are derived from models that are even less well constrained. These calculations demonstrate the importance of gaining a better understanding of historical ozone changes.

The role of natural factors in constraining long-term tropospheric ozone trends over Southern China

2020 ◽  
Vol 220 ◽  
pp. 117060 ◽  
Author(s):  
Xi Chen ◽  
Buqing Zhong ◽  
Fuxiang Huang ◽  
Xuemei Wang ◽  
Sayantan Sarkar ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Southern China ◽  
Natural Factors ◽  
Ozone Trends

scholarly journals Stratospheric impact on tropospheric ozone variability and trends: 1990–2009

2013 ◽  
Vol 13 (2) ◽  
pp. 649-674 ◽  
Author(s):  
P. G. Hess ◽  
R. Zbinden
Keyword(s):  
Tropospheric Ozone ◽  
Large Scale ◽  
Transport Model ◽  
Spatial Scales ◽  
Stratospheric Ozone ◽  
Atmospheric Model ◽  
Chemical Transport Model ◽  
Ozone Trends ◽  
Environmental Prediction

Abstract. The influence of stratospheric ozone on the interannual variability and trends in tropospheric ozone is evaluated between 30 and 90° N from 1990–2009 using ozone measurements and a global chemical transport model, the Community Atmospheric Model with chemistry (CAM-chem). Long-term measurements from ozonesondes, at 150 and 500 hPa, and the Measurements of OZone and water vapour by in-service Airbus aircraft programme (MOZAIC), at 500 hPa, are analyzed over Japan, Canada, the Eastern US and Northern and Central Europe. The measurements generally emphasize northern latitudes, although the simulation suggests that measurements over the Canadian, Northern and Central European regions are representative of the large-scale interannual ozone variability from 30 to 90° N at 500 hPa. CAM-chem is run with input meteorology from the National Center for Environmental Prediction; a tagging methodology is used to identify the stratospheric contribution to tropospheric ozone concentrations. A variant of the synthetic ozone tracer (synoz) is used to represent stratospheric ozone. Both the model and measurements indicate that on large spatial scales stratospheric interannual ozone variability drives significant tropospheric variability at 500 hPa and the surface. In particular, the simulation and the measurements suggest large stratospheric influence at the surface sites of Mace Head (Ireland) and Jungfraujoch (Switzerland) as well as many 500 hPa measurement locations. Both the measurements and simulation suggest the stratosphere has contributed to tropospheric ozone trends. In many locations between 30–90° N 500 hPa ozone significantly increased from 1990–2000, but has leveled off since (from 2000–2009). The simulated global ozone budget suggests global stratosphere-troposphere exchange increased in 1998–1999 in association with a global ozone anomaly. Discrepancies between the simulated and measured ozone budget include a large underestimation of measured ozone variability and discrepancies in long-term stratospheric ozone trends. This suggests the need for more sophisticated simulations including better representations of stratospheric chemistry and circulation.

Comment on Long Term Ozone Trends

1986 ◽  
Vol 36 (3) ◽  
pp. 271-272 ◽  
Author(s):  
Herbert C. McKee
Keyword(s):  
Ozone Trends

Wilderness Camping as a Therapy for Emotionally Disturbed Children: A Critical Review

1979 ◽  
Vol 45 (8) ◽  
pp. 628-635 ◽  
Author(s):  
E. Sandra Byers
Keyword(s):  
Critical Review ◽  
Emotionally Disturbed ◽  
Evaluation Research ◽  
Disturbed Child ◽  
Short Term ◽  
Minimal Support ◽  
Therapeutic Program ◽  
Good Setting ◽  
Therapeutic Camping

The wilderness camp has been described as a particularly good setting for treatment of the emotionally disturbed child. This article summarizes the current literature on therapeutic camping, including the nature of existing programs, rationales for the superiority of camping as a therapeutic program, and evaluation of existing programs. The results of program evaluation research reported in the literature provide only minimal support for any particular effectiveness ascribed to therapeutic camping in terms of either short term or long term therapeutic outcome. This is seen to be largely due to inadequate investigation of the process and/or the outcome of therapeutic camping.

scholarly journals Reconciling differences in stratospheric ozone composites

2017 ◽  
Vol 17 (20) ◽  
pp. 12269-12302 ◽  
Author(s):  
William T. Ball ◽  
Justin Alsing ◽  
Daniel J. Mortlock ◽  
Eugene V. Rozanov ◽  
Fiona Tummon ◽  
...  
Keyword(s):  
Time Series ◽  
Likelihood Function ◽  
Stratospheric Ozone ◽  
Gaussian Mixture ◽  
Robust Estimate ◽  
Mixture Density ◽  
Source Data ◽  
Ozone Trends ◽  
Decadal Trend

Abstract. Observations of stratospheric ozone from multiple instruments now span three decades; combining these into composite datasets allows long-term ozone trends to be estimated. Recently, several ozone composites have been published, but trends disagree by latitude and altitude, even between composites built upon the same instrument data. We confirm that the main causes of differences in decadal trend estimates lie in (i) steps in the composite time series when the instrument source data changes and (ii) artificial sub-decadal trends in the underlying instrument data. These artefacts introduce features that can alias with regressors in multiple linear regression (MLR) analysis; both can lead to inaccurate trend estimates. Here, we aim to remove these artefacts using Bayesian methods to infer the underlying ozone time series from a set of composites by building a joint-likelihood function using a Gaussian-mixture density to model outliers introduced by data artefacts, together with a data-driven prior on ozone variability that incorporates knowledge of problems during instrument operation. We apply this Bayesian self-calibration approach to stratospheric ozone in 10° bands from 60° S to 60° N and from 46 to 1 hPa (∼ 21–48 km) for 1985–2012. There are two main outcomes: (i) we independently identify and confirm many of the data problems previously identified, but which remain unaccounted for in existing composites; (ii) we construct an ozone composite, with uncertainties, that is free from most of these problems – we call this the BAyeSian Integrated and Consolidated (BASIC) composite. To analyse the new BASIC composite, we use dynamical linear modelling (DLM), which provides a more robust estimate of long-term changes through Bayesian inference than MLR. BASIC and DLM, together, provide a step forward in improving estimates of decadal trends. Our results indicate a significant recovery of ozone since 1998 in the upper stratosphere, of both northern and southern midlatitudes, in all four composites analysed, and particularly in the BASIC composite. The BASIC results also show no hemispheric difference in the recovery at midlatitudes, in contrast to an apparent feature that is present, but not consistent, in the four composites. Our overall conclusion is that it is possible to effectively combine different ozone composites and account for artefacts and drifts, and that this leads to a clear and significant result that upper stratospheric ozone levels have increased since 1998, following an earlier decline.

scholarly journals Statistical regularization for trend detection: an integrated approach for detecting long-term trends from sparse tropospheric ozone profiles

2020 ◽  
Vol 20 (16) ◽  
pp. 9915-9938
Author(s):  
Kai-Lan Chang ◽  
Owen R. Cooper ◽  
Audrey Gaudel ◽  
Irina Petropavlovskikh ◽  
Valérie Thouret
Keyword(s):  
Time Series ◽  
Tropospheric Ozone ◽  
Sampling Frequency ◽  
Basic Trend ◽  
Trend Detection ◽  
Percentage Error ◽  
Statistical Regularization ◽  
Vertical Correlation ◽  
Accurate Quantification

Abstract. Detecting a tropospheric ozone trend from sparsely sampled ozonesonde profiles (typically once per week) is challenging due to the short-lived anomalies in the time series resulting from ozone's high temporal variability. To enhance trend detection, we have developed a sophisticated statistical approach that utilizes a geoadditive model to assess ozone variability across a time series of vertical profiles. Treating the profile time series as a set of individual time series on discrete pressure surfaces, a class of smoothing spline ANOVA (analysis of variance) models is used for the purpose of jointly modeling multiple correlated time series (on separate pressure surfaces) by their associated seasonal and interannual variabilities. This integrated fit method filters out the unstructured variation through a statistical regularization (i.e., a roughness penalty) by taking advantage of the additional correlated data points available on the pressure surfaces above and below the surface of interest. We have applied this technique to the trend analysis of the vertically correlated time series of tropospheric ozone observations from (1) IAGOS (In-service Aircraft for a Global Observing System) commercial aircraft profiles above Europe and China throughout 1994–2017 and (2) NOAA GML's (Global Monitoring Laboratory) ozonesonde records at Hilo, Hawaii, (1982–2018) and Trinidad Head, California (1998–2018). We illustrate the ability of this technique to detect a consistent trend estimate and its effectiveness in reducing the associated uncertainty in the profile data due to the low sampling frequency. We also conducted a sensitivity analysis of frequent IAGOS profiles above Europe (approximately 120 profiles per month) to determine how many profiles in a month are required for reliable long-term trend detection. When ignoring the vertical correlation, we found that a typical sampling strategy (i.e. four profiles per month) might result in 7 % of sampled trends falling outside the 2σ uncertainty interval derived from the full dataset with an associated 10 % of mean absolute percentage error. Based on a series of sensitivity studies, we determined optimal sampling frequencies for (1) basic trend detection and (2) accurate quantification of the trend. When applying the integrated fit method, we find that a typical sampling frequency of four profiles per month is adequate for basic trend detection; however, accurate quantification of the trend requires 14 profiles per month. Accurate trend quantification can be achieved with only 10 profiles per month if a regular sampling frequency is applied. In contrast, the standard separated fit method, which ignores the vertical correlation between pressure surfaces, requires 8 profiles per month for basic trend detection and 18 profiles per month for accurate trend quantification. While our method improves trend detection from sparse datasets, the key to substantially reducing the uncertainty is to increase the sampling frequency.

scholarly journals Tropospheric Ozone Assessment Report: Present-day ozone distribution and trends relevant to human health

Elem Sci Anth ◽  
2018 ◽  
Vol 6 ◽  
Author(s):  
Zoë L. Fleming ◽  
Ruth M. Doherty ◽  
Erika von Schneidemesser ◽  
Christopher S. Malley ◽  
Owen R. Cooper ◽  
...  
Keyword(s):  
East Asia ◽  
Tropospheric Ozone ◽  
Warm Season ◽  
The Other ◽  
Daily Maximum ◽  
Assessment Report ◽  
Common Trend ◽  
Nighttime Lights ◽  
Ozone Trends ◽  
Other World

This study quantifies the present-day global and regional distributions (2010–2014) and trends (2000–2014) for five ozone metrics relevant for short-term and long-term human exposure. These metrics, calculated by the Tropospheric Ozone Assessment Report, are: 4th highest daily maximum 8-hour ozone (4MDA8); number of days with MDA8 > 70 ppb (NDGT70), SOMO35 (annual Sum of Ozone Means Over 35 ppb) and two seasonally averaged metrics (3MMDA1; AVGMDA8). These metrics were explored at ozone monitoring sites worldwide, which were classified as urban or non-urban based on population and nighttime lights data. Present-day distributions of 4MDA8 and NDGT70, determined predominantly by peak values, are similar with highest levels in western North America, southern Europe and East Asia. For the other three metrics, distributions are similar with North–South gradients more prominent across Europe and Japan. Between 2000 and 2014, significant negative trends in 4MDA8 and NDGT70 occur at most US and some European sites. In contrast, significant positive trends are found at many sites in South Korea and Hong Kong, with mixed trends across Japan. The other three metrics have similar, negative trends for many non-urban North American and some European and Japanese sites, and positive trends across much of East Asia. Globally, metrics at many sites exhibit non-significant trends. At 59% of all sites there is a common direction and significance in the trend across all five metrics, whilst 4MDA8 and NDGT70 have a common trend at ~80% of all sites. Sensitivity analysis shows AVGMDA8 trends differ with averaging period (warm season or annual). Trends are unchanged at many sites when a 1995–2014 period is used; although fewer sites exhibit non-significant trends. Over the longer period 1970–2014, most Japanese sites exhibit positive 4MDA8/SOMO35 trends. Insufficient data exist to characterize ozone trends for the rest of Asia and other world regions.

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