Global climate models that do not include interactive middle atmosphere chemistry, such as most of those contributing to the Coupled Model Intercomparison Project Phase 5, typically specify ...stratospheric ozone using monthly mean, zonal mean values and linearly interpolate to the time resolution of the model. We show that this method leads to significant biases in the simulated climate of the southern hemisphere (SH) over the late twentieth century. Previous studies have attributed similar biases in simulated SH climate change to the effect of the spatial smoothing of the specified ozone, i.e., to using zonal mean concentrations. We here show that the bias in climate trends due to undersampling of the rapid temporal changes in ozone during the seasonal evolution of the Antarctic ozone hole is considerable and reaches all the way into the troposphere. Our results suggest that the bias can be substantially reduced by specifying daily ozone concentrations.
Key Points
Climate trends in models depend on the input frequency of stratospheric ozoneZonal asymmetries in ozone do not solely cause biases in climate simulationsModel simulations are greatly improved by specifying daily ozone values
Ozone remains an important phytotoxic air pollutant and is also recognized as a significant greenhouse gas. In North America, Europe, and Asia, incidence of high concentrations is decreasing, but ...background levels are steadily rising. There is a need to develop a biologically significant and usable standard for ozone. We compare the strengths and weaknesses of concentration-based, exposure-based and threshold-based indices, such as SUM60 and AOT40, and examine the O
3 flux concept. We also present major challenges to the development of an air quality standard for ozone that has both biological significance and practicality in usage.
Current standards do not protect vegetation from ozone, but progress is being made.
Ozone (O
3
) is a photochemically formed reactive gas responsible for a decreasing carbon assimilation in plant ecosystems. Present in the atmosphere in trace concentrations (less than 100 ppbv), ...this molecule is capable of inhibiting carbon assimilation in agricultural and forest ecosystems. Ozone-risk assessments are typically based on manipulative experiments. Present regulations regarding critical ozone levels are mostly based on an estimated accumulated exposure over a given threshold concentration. There is however a scientific consensus over flux estimates being more accurate, because they include plant physiology analyses and different environmental parameters that control the uptake—that is, not just the exposure—of O
3
. While O
3
is a lot more difficult to measure than other non-reactive greenhouse gases, UV-based and chemiluminescence sensors enable precise and fast measurements and are therefore highly desirable for eddy covariance studies. Using micrometeorological techniques in association with latent heat flux measurements in the field allows for the partition of ozone fluxes into the stomatal and non-stomatal sinks along the soil-plant continuum. Long-term eddy covariance measurements represent a key opportunity in estimating carbon assimilation at high-temporal resolutions, in an effort to study the effect of climate change on photosynthetic mechanisms. Our aim in this work is to describe potential of O
3
flux measurement at the canopy level for ozone-risk assessment in established long-term monitoring networks.
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Polyurethane elastomers have a combination of excellent mechanical, physical and chemical properties along with exceptional biocompatibility. Therefore, these elastomeric systems are ...used in a diverse range of indoor, outdoor, underwater and biomedical applications. However, under certain conditions polyurethane elastomers undergo degradation, resulting in modified properties during usage or even complete failure. The degradation will not only severely affect the quality of the associated items, devices, or instruments, but may also cause catastrophic outcomes risking people’s safety and health. This review presents a comprehensive survey of the literature regarding various types of degradation of polyurethane elastomers, including photo-, thermal, ozonolytic, hydrolytic, chemical, enzymatic, in-vivo/in-vitro oxidative, biological, and mechanical degradation. The stability of polyurethane elastomers based on different building blocks of macrodiols (polyester, polyether, polycarbonate, polybutadiene, and polyisobutylene), isocyanates (aromatic and aliphatic), and chain extenders (diols, triols, and diamines) are summarised, and the mechanisms of different types of degradation are presented. The chemical components significantly influence not only the material structure and properties but also the degradative stability. Focussing on the components, we explore strategies for the enhancement of polyurethane stability through chemistry and engineering. A range of stabilizers, including both organic and inorganic additives for better stability against different types of degradation, are discussed, with a focus on their efficacy and mechanisms of action. A perspective on novel polyurethane materials with desired structures and properties combined with exceptional stability is also provided.
The January 2022 eruption of the Hunga Tonga-Hunga Ha'apai underwater volcano injected a
large amount of water vapor into the mid-stratosphere. This study uses model simulations to
investigate the ...resulting stratospheric impacts out to 2031. Maximum radiatively-driven model temperature changes occur in the Southern Hemisphere (SH) subtropics in April–May 2022, with warming of ∼1 K in the lower stratosphere and cooling of 3 K in the mid-stratosphere. The radiative cooling combined with adiabatic cooling driven by the quasi-biennial oscillation meridional circulation explains the near-record cold anomaly observed in the SH subtropical mid-stratosphere. Projected ozone responses maximize in 2023–2024 as the water vapor plume is transported globally throughout the stratosphere and mesosphere. The excess H2O increases the OH radical, causing a negative global ozone response (2%–10%) in the upper stratosphere and mesosphere due to increased odd hydrogen-ozone loss, and a small positive ozone response (0.5%–1%) in the mid-stratosphere due to interference of the NOx catalytic loss cycle by the additional OH. In the lower stratosphere, the excess H2O is projected to increase polar stratospheric clouds and springtime halogen-ozone loss, enhancing the Antarctic ozone hole by 25–30 DU in 2023. Arctic impact is small, with maximum additional ozone loss of 4–5 DU projected in spring 2024. These responses diminish after 2024 to be quite small by 2031, as the excess H2O is removed from the stratosphere with a 2.5-year e-folding time. Given the year-to-year variability of the stratosphere, the magnitudes of these ozone responses may be below the threshold of detectability in observations.
The additive time-series decomposition analysis was performed on National Oceanic and Atmospheric Administration Solar Backscatter Ultraviolet Instrument Merge satellite dataset version 8.6 for the ...period January 1979 to December 2019 with an objective to detect and apportion long-term trends present in the total ozone column (TOC) and the long-term trends exist in the respective ozone contents present in the vertical sub-columns constituting the TOC viz. upper, middle and lower stratosphere as well as near-surface for the tropical region. Linear regression analysis was performed on the deseasonalized monthly mean time series of TOC and corresponding ozone contents present in each partitioned layer for three different time spans, viz. 1979–2019 (complete time series), 1979–1998 (pre-inflection years), and 1999–2019 (post-inflection years), where 1998 was taken as inflection year. For the complete time-series, statistically significant negative trends were observed in TOC and corresponding ozone contents in the sub-columns over most of the tropical region. Expectedly, during pre-inflection years, strong negative trends were noted for TOC and ozone contents in the partitioned vertical layers. In contrast, during the post-inflection year time span, long-term trends in TOC were statistically insignificant over two-third of the tropical region, but one-third of the subtropical region exhibited negative trends in TOC. During this time span, positive trends were observed in the ozone contents present in the upper stratospheric sub-column. However, negative trends in ozone contents persisted in the middle and the lower stratosphere. It was interesting to note that the ozone contents confined in near-surface layer manifested strong negative trends during pre-inflection years and the same reversed into strong positive trends that in post-inflection span. The observed, contrasting, long-term trends and variability in the respective partitioned layer of the TOC confounded any clear sign of recovery in the TOC over the tropical region. The continuation of declining trends in the middle stratosphere and increasing trends in the near-surface layer of ozone contents is a matter of concern.
The Geostationary Environment Monitoring Spectrometer (GEMS) is scheduled to
be launched in 2019–2020 on board the GEO-KOMPSAT (GEOstationary KOrea
Multi-Purpose SATellite)-2B, contributing as the ...Asian partner of the global
geostationary constellation of air quality monitoring. To support this air
quality satellite mission, we perform a cross-evaluation of simulated GEMS
ozone profile retrievals from OMI (Ozone Monitoring Instrument) data based
on the optimal estimation and ozonesonde measurements within the GEMS
domain, covering from 5∘ S (Indonesia) to
45∘ N (south of the Russian border) and from
75 to 145∘ E. The comparison between
ozonesonde and GEMS shows a significant dependence on ozonesonde types.
Ozonesonde data measured by modified Brewer–Mast (MBM) at Trivandrum and
New Delhi show inconsistent seasonal variabilities in tropospheric ozone
compared to carbon–iodine (CI) and electrochemical condensation cell (ECC)
ozonesondes at other stations in a similar latitude regime. CI ozonesonde
measurements are negatively biased relative to ECC measurements by 2–4 DU;
better agreement is achieved when simulated GEMS ozone retrievals are
compared to ECC measurements. ECC ozone data at Hanoi, Kuala Lumpur, and
Singapore show abnormally worse agreements with simulated GEMS retrievals
than other ECC measurements. Therefore, ECC ozonesonde measurements at Hong
Kong, Pohang, Naha, Sapporo, and Tsukuba are finally identified as an
optimal reference dataset. The accuracy of simulated GEMS retrievals is
estimated to be ∼5.0 % for both tropospheric and
stratospheric column ozone with the precision of 15 % and 5 %, which
meets the GEMS ozone requirements.
Vertical measurements of ozone (O3) within the 3000-m lower troposphere were obtained using an O3 lidar to investigate the contribution of the interactions between the transport and boundary layer ...processes to the surface O3 levels in urban Shanghai, China during July 23–28, 2017. An extremely severe pollution episode with a maximum hourly O3 mixing ratio of 160.4 ppb was observed. In addition to enhanced local photochemical production, both downward and advection transport in the lower troposphere may have played important roles in forming the pollution episode. The O3-rich air masses in the lower free troposphere primarily originated from central China and the northern Yangtze River Delta (YRD) region. The downward transport of O3 from the lower free troposphere may have an average contribution of up to 49.1% to the daytime (09:00–16:00 local time) surface O3 in urban Shanghai during the pollution episode (July 23–26, 2017). As for the advection transport, large amounts of O3 were transported outward from Shanghai in the planetary boundary layer under the influence of southeasterly winds during the field study. In this condition, the boundary-layer O3 that was transported downward from the free troposphere in Shanghai could be transported back to the northern YRD region and accumulated therein, leading to the occurrence of severe O3 pollution events over the whole YRD region. Our results indicate that effective regional emission control measures are urgently required to mitigate O3 pollution in the YRD region.
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•The surface O3 episode in Shanghai was closely associated with downward transport.•Contributions of downward transport to surface O3 varied between 12.6% and 78.3%.•O3 was transported to Shanghai from the northern YRD in the lower free troposphere.•O3 was transported to the northern YRD from Shanghai in the boundary layer.
In this review, instead of summarizing all the advances and progress achieved in stratospheric research, the main advances and new developments in stratosphere-troposphere coupling and stratospheric ...chemistry-climate interactions are summarized, and some outstanding issues and grand challenges are discussed. A consensus has been reached that the stratospheric state is an important source of improving the predictability of the troposphere on sub-seasonal to seasonal (S2S) time scales and beyond. However, applying stratospheric signals in operational S2S forecast models remains a challenge because of model deficiencies and the complexities of the underlying mechanisms of stratosphere-troposphere coupling. Stratospheric chemistry, which controls the magnitude and distribution of many important climate-forcing agents, plays a critical role in global climate change. Convincing evidence has been found that stratospheric ozone depletion and recovery have caused significant tropospheric climate changes, and more recent studies have revealed that stratospheric ozone variations can even exert an impact on SSTs and sea ice. The climatic impacts of stratospheric aerosols and water vapor are also important. Although their quantitative contributions to radiative forcing have been reasonably well quantified, there still exist large uncertainties in their long-term impacts on climate. The advances and new levels of understanding presented in this review suggest that whole-atmosphere interactions need to be considered in future for a better and more thorough understanding of stratosphere-troposphere coupling and its role in climate change.
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