Polar stratospheric clouds (PSCs) play important roles in stratospheric ozone depletion during winter and spring at high latitudes (e.g., the Antarctic ozone hole). PSC particles provide sites for ...heterogeneous reactions that convert stable chlorine reservoir species to radicals that destroy ozone catalytically. PSCs also prolong ozone depletion by delaying chlorine deactivation through the removal of gas‐phase HNO3 and H2O by sedimentation of large nitric acid trihydrate (NAT) and ice particles. Contemporary observations by the spaceborne instruments Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), Microwave Limb Sounder (MLS), and Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) have provided an unprecedented polar vortex‐wide climatological view of PSC occurrence and composition in both hemispheres. These data have spurred advances in our understanding of PSC formation and related dynamical processes, especially the firm evidence of widespread heterogeneous nucleation of both NAT and ice PSC particles, perhaps on nuclei of meteoritic origin. Heterogeneous chlorine activation appears to be well understood. Reaction coefficients on/in liquid droplets have been measured accurately, and while uncertainties remain for reactions on solid NAT and ice particles, they are considered relatively unimportant since under most conditions chlorine activation occurs on/in liquid droplets. There have been notable advances in the ability of chemical transport and chemistry‐climate models to reproduce PSC temporal/spatial distributions and composition observed from space. Continued spaceborne PSC observations will facilitate further improvements in the representation of PSC processes in global models and enable more accurate projections of the evolution of polar ozone and the global ozone layer as climate changes.
Plain Language Summary
Polar stratospheric clouds (PSCs) occur during winter and early spring in the polar stratosphere, when temperatures are low enough to enable cloud formation despite the extremely dry conditions. Ground‐based PSC sightings date back to the late 19th century, but they were little more than a scientific curiosity until the discovery of the Antarctic ozone hole in 1985. Soon thereafter, it was shown that PSCs play a crucial role in converting stable halogen (mainly chlorine) species of anthropogenic origin into reactive gases that rapidly destroy ozone. Considerable progress was made over the next two decades in quantifying these processes through laboratory studies, field campaigns, and limited spaceborne observations. We are now reaping the benefits of new PSC observations over the entire polar regions from three complementary 21st century spaceborne instruments. This study reviews these instruments and highlights new findings on PSC occurrence and composition. These datasets have also triggered advances in understanding how PSCs form and the influence of atmospheric dynamics, as well as improvements in how detailed cloud processes are approximated in global models. This will ultimately lead to better predictions of how quickly the stratospheric ozone layer will recover from human influence as global climate changes in the future.
Key Points
We provide a new vortex‐wide climatology of polar stratospheric cloud occurrence and composition based on 21st century satellite data
We review advances in understanding cloud formation, the role of dynamical processes, and heterogeneous chlorine activation
We highlight improvements in techniques for parameterizing polar stratospheric clouds and their effects in global models
The Environmental Effects Assessment Panel of the Montreal Protocol under the United Nations Environment Programme evaluates effects on the environment and human health that arise from changes in the ...stratospheric ozone layer and concomitant variations in ultraviolet (UV) radiation at the Earth’s surface. The current update is based on scientific advances that have accumulated since our last assessment (Photochem and Photobiol Sci 20(1):1–67, 2021). We also discuss how climate change affects stratospheric ozone depletion and ultraviolet radiation, and how stratospheric ozone depletion affects climate change. The resulting interlinking effects of stratospheric ozone depletion, UV radiation, and climate change are assessed in terms of air quality, carbon sinks, ecosystems, human health, and natural and synthetic materials. We further highlight potential impacts on the biosphere from extreme climate events that are occurring with increasing frequency as a consequence of climate change. These and other interactive effects are examined with respect to the benefits that the Montreal Protocol and its Amendments are providing to life on Earth by controlling the production of various substances that contribute to both stratospheric ozone depletion and climate change.
El maltrato infantil es uno de los mayores problemas sociales y económicos a nivel mundial. Entre las personas que han sido víctimas del MI existe una alta prevalencia de violencia, abuso de drogas y ...enfermedades psiquiátricas, entre otros. A nivel fisiológico, el eje hipotálamo-pituitaria-adrenal y la respuesta al estrés están directamente relacionados con esta prevalencia. Además, en los últimos años, ha aumentado la preocupación por el efecto de la contaminación sobre la salud humana. El objetivo de este proyecto es determinar el efecto de la exposición crónica a un ambiente contaminado con ozono, sobre algunos biomarcadores, en un modelo animal de privación materna. Se medirá cómo afecta la exposición a ozono sobre la capacidad cognitiva y el estado de ansiedad. Además, se analizará la variación de corticosterona y ACTH en plasma tras la exposición a un estresor agudo. Por último, se analizará el volumen del hipocampo y sus subáreas, así como el grado de metilación del exón promotor del receptor de glucocorticoides 1F y del exón promotor de vasopresina. Con el presente trabajo se pretende ampliar el conocimiento sobre el desarrollo cognitivo de niños que han sufrido maltrato infantil.
A four‐step adaptive ozone trend estimation scheme is proposed by integrating multivariate linear regression (MLR) and ensemble empirical mode decomposition (EEMD) to analyze the long‐term ...variability of total column ozone from a set of four observational and reanalysis total ozone data sets, including the rarely explored ERA‐Interim total ozone reanalysis, from 1979 to 2009. Consistency among the four data sets was first assessed, indicating a mean relative difference of 1% and root‐mean‐square error around 2% on average, with respect to collocated ground‐based total ozone observations. Nevertheless, large drifts with significant spatiotemporal inhomogeneity were diagnosed in ERA‐Interim after 1995. To emphasize long‐term trends, natural ozone variations associated with the solar cycle, quasi‐biennial oscillation, volcanic aerosols, and El Niño–Southern Oscillation were modeled with MLR and then removed from each total ozone record, respectively, before performing EEMD analyses. The resulting rates of change estimated from the proposed scheme captured the long‐term ozone variability well, with an inflection time of 2000 clearly detected. The positive rates of change after 2000 suggest that the ozone layer seems to be on a healing path, but the results are still inadequate to conclude an actual recovery of the ozone layer, and more observational evidence is needed. Further investigations suggest that biases embedded in total ozone records may significantly impact ozone trend estimations by resulting in large uncertainty or even negative rates of change after 2000.
Key Points
Total ozone from ERA‐Interim ozone reanalysis are significantly biased after 1995
The proposed four‐step adaptive ozone trend estimation scheme works effectively in assessing the long‐term variability of the ozone layer
Positive rates of change after 2000 seem to indicate an early recovery sign of the ozone layer
Tremendous efforts have been made to reduce the severe air pollution in China since 2013. However, the annual and peak fine particulate matter (PM
) concentrations during severe events in winter did ...not always reduce as expected. This is partially due to the inter-annual variation of meteorology, which affects the emission, transport, transformation, and deposition processes of air pollutants. In this study, the responses of PM
and ozone (O
) concentrations to changes in emission and meteorology from 2013 to 2015 were investigated based on ambient measurements and the Community Multi-Scale Air Quality (CMAQ) model simulations with anthropogenic emissions. It is found that emission reductions in 2014 and 2015 effectively reduced PM
concentrations by 23.9 and 43.5 μg/m
, respectively, but was partially counteracted by unfavorable meteorology. The negative effects from unfavorable meteorology were significant in extreme pollution events. For example, in December 2015, unfavorable meteorology caused a great increase (90 μg/m
) of PM
in Beijing. Reduction of primary PM and gaseous precursors led to 13.4 and 16.5 ppb increase of O
-8 h daily concentrations in the summertime in 2014 and 2015 in comparison of 2013, which was likely caused by the increase of solar actinic flux due to PM reduction. In addition, reduction of nitrogen oxides (NOx) emissions in areas with negative NOx-O
sensitivity could lead to an increase of O
formation when the reduction of volatile organic compounds (VOCs) was not sufficient. This unintended enhanced O
formation could also lead to higher O
in downwind areas. This study emphasizes the role of meteorology in pollution control, validates the effectiveness of PM
control measures in China, and highlights the importance of appropriate joint reduction of NOx and VOCs to simultaneously decrease O
and PM
for higher air quality.
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