Global Ozone Change Research Articles

Investigating changes in global distribution of Ozone in 2018 using [formula omitted]-means clustering algorithm

Ozone is an active gas in the atmosphere. Its content is quite low, but it plays an important role in protecting the health of human beings and other living things on earth. Ozone circulates in the atmosphere, and its total distribution and variation trend are related to geographical position. In this paper, we collected global Ozone tendency data and investigated the changes in global distribution of Ozone in 2018 using k-means clustering algorithm. We observed that (1) the global Ozone tendency can be broadly divided into four regions; (2) the data with a large variation range of total Ozone tendency is mainly concentrated near the sea–land boundary, and their distribution is similar to the coastline contour to some extent; (3) after clustering, the concentration area of the data with great changes in the total Ozone tendency is roughly x-shaped distribution, and the acute angle between the data and the latitude line is between 25° and 45°. Our findings can contribute to a clearer understanding and analysis of the tendency of global Ozone change and help mitigate the Ozone hole problem in different regions.

Identifying the ozone-neutral aircraft cruise altitude

Depletion of stratospheric ozone, and the associated increase in population exposure to UV radiation, is an environmental consequence of high-altitude, supersonic aviation. Assessments of the impacts of emissions from subsonic aircraft – which fly at lower altitudes – have instead shown that they produce a net increase, rather than decrease, in global net ozone, suggesting the existence of an intermediate “column ozone neutral” cruise altitude. Knowing this altitude and its variation with factors such as latitude, season, and fuel composition could provide a pathway towards reducing the environmental impacts of aviation, but would require a prohibitive number of atmospheric simulations. We instead use the newly developed GEOS-Chem tropospheric-stratospheric adjoint to identify the location of the column ozone-neutral aircraft cruise altitude as a function of these factors. We show that, although the mean ozone neutral altitude is at 13.5 km globally, this varies from 14.6 km to 12.5 km between the equator and 60°N. This altitude varies by less than a kilometer between seasons, but the net depletion resulting from flying at greater altitudes varies by a factor of two. We also find that eliminating fuel sulfur would result in a neutral altitude 0.5–1.0 km greater than when conventional jet fuel is burned. Our results imply that a low Mach number supersonic aircraft burning low-sulfur fuel (e.g. biofuels) may be able to achieve net zero global ozone change. However, for a fleet to achieve ozone neutrality will require careful consideration of the non-linear variation in sensitivity with altitude and latitude.

Roles of transport and chemistry processes in global ozone change on interannual and multidecadal time scales

This study investigates ozone changes and the individual impacts of transport and chemistry on those changes. We specifically examine (1) variation related to El Niño Southern Oscillation, which is a dominant mode of interannual variation of tropospheric ozone, and (2) long‐term change between the 2000s and 2100s. During El Niño, the simulated ozone shows an increase (1 ppbv/K) over Indonesia, a decrease (2–10 ppbv/K) over the eastern Pacific in the tropical troposphere, and an increase (50 ppbv/K) over the eastern Pacific in the midlatitude lower stratosphere. These variations fundamentally agree with those observed by Microwave Limb Sounder/Tropospheric Emission Spectrometer instruments. The model demonstrates that tropospheric chemistry has a strong impact on the variation over the eastern Pacific in the tropical lower troposphere and that transport dominates the variation in the midlatitude lower stratosphere. Between the 2000s and 2100s, the model predicts an increase in the global burden of stratospheric ozone (0.24%/decade) and a decrease in the global burden of tropospheric ozone (0.82%/decade). The increase in the stratospheric burden is controlled by stratospheric chemistry. Tropospheric chemistry reduces the tropospheric burden by 1.07%/decade. However, transport (i.e., stratosphere‐troposphere exchange and tropospheric circulation) causes an increase in the burden (0.25%/decade). Additionally, we test the sensitivity of ozone changes to increased horizontal resolution of the representation of atmospheric circulation and advection apart from any aspects of the nonlinearity of chemistry sensitivity to horizontal resolution. No marked difference is found in medium‐resolution or high‐resolution simulations, suggesting that the increased horizontal resolution of transport has a minor impact.

Simulation of changes in global ozone and atmospheric dynamics in the 21st century with the chemistry-climate model SOCOL

The solar climate ozone links (SOCOL) three-dimensional chemistry-climate model is used to estimate changes in the ozone and atmospheric dynamics over the 21st century. With this model, four numerical time-slice experiments were conducted for 1980, 2000, 2050, and 2100 conditions. Boundary conditions for sea-surface temperatures, sea-ice parameters, and concentrations of greenhouse and ozone-depleting gases were set following the IPCC A1B scenario and the WMO A1 scenario. From the model results, a statistically significant cooling of the model stratosphere was obtained to be 4–5 K for 2000–2050 and 3–5 K for 2050–2100. The temperature of the lower atmosphere increases by 2–3 K over the 21st century. Tropospheric heating significantly enhances the activity of planetary-scale waves at the tropopause. As a result, the Eliassen-Palm flux divergence considerable increases in the middle and upper stratosphere. The intensity of zonal circulation decreases and the meridional residual circulation increases, especially in the winter-spring period of each hemisphere. These dynamic changes, along with a decrease in the concentrations of ozone-depleting gases, result in a faster growth of O3 outside the tropics. For example, by 2050, the total ozone in the middle and high latitudes approaches its model level of 1980 and the ozone hole in Antarctica fills up. The superrecovery of the model ozone layer in the middle and high latitudes of both hemispheres occurs in 2100. The tropical ozone layer recovers far less slowly, reaching a 1980 level only by 2100.

Radiative forcing from particle emissions by future supersonic aircraft

Abstract. In this work we focus on the direct radiative forcing (RF) of black carbon (BC) and sulphuric acid particles emitted by future supersonic aircraft, as well as on the ozone RF due to changes produced by emissions of both gas species (NOx, H2O) and aerosol particles capable of affecting stratospheric ozone chemistry. Heterogeneous chemical reactions on the surface of sulphuric acid stratospheric particles (SSA-SAD) are the main link between ozone chemistry and supersonic aircraft emissions of sulphur precursors (SO2) and particles (H2O–H2SO4). Photochemical O3 changes are compared from four independent 3-D atmosphere-chemistry models (ACMs), using as input the perturbation of SSA-SAD calculated in the University of L'Aquila model, which includes on-line a microphysics code for aerosol formation and growth. The ACMs in this study use aircraft emission scenarios for the year 2050 developed by AIRBUS as a part of the EU project SCENIC, assessing options for fleet size, engine technology (NOx emission index), Mach number, range and cruising altitude. From our baseline modeling simulation, the impact of supersonic aircraft on sulphuric acid aerosol and BC mass burdens is 53 and 1.5 μg/m2, respectively, with a direct RF of −11.4 and 4.6 mW/m2 (net RF=−6.8 mW/m2). This paper discusses the similarities and differences amongst the participating models in terms of changes to O3 precursors due to aircraft emissions (NOx, HOx,Clx,Brx) and the stratospheric ozone sensitivity to them. In the baseline case, the calculated global ozone change is −0.4 ±0.3 DU, with a net radiative forcing (IR+UV) of −2.5± 2 mW/m2. The fraction of this O3-RF attributable to SSA-SAD changes is, however, highly variable among the models, depending on the NOx removal efficiency from the aircraft emission regions by large scale transport.

Ozone climatology, trends, and substances that control ozone

Ozone decline observed in the stratosphere over the past three decades has resulted from the accumulation of chlorine‐ and bromine‐containing ozone‐depleting substances (ODSs) in the atmosphere. Production of most of these gases is regulated by the Montreal Protocol and its Amendments and Adjustments. The latest observations show a decline in major ODSs in the troposphere as a result of these regulations. Observed changes in global ozone are in line with those expected based on changes in stratospheric levels of chlorine and bromine. A change in the rate of ozone decline was observed in the mid‐1990s. This paper gives a brief overview of the present knowledge of distribution, variability, and long‐term trends in column ozone and ozone profiles, with a focus on observational results and particularly on Canadian data analysis.

Comparison of the Odin/OSIRIS stratospheric ozone profiles with coincident POAM III and ozonesonde measurements

We present first statistical comparison results for stratospheric ozone density profiles retrieved from Odin/OSIRIS limb scattered radiance with 1220 coincident POAM III and 205 coincident ozonesonde measurements. Profiles are compared on a monthly basis from November 2001 to October 2002. Most of the time, differences between OSIRIS mean profiles and those measured by POAM III and ozonesondes were 5–7% between 15 km and 32 km, and within 15% above 32 km. In April–July 2002, OSIRIS mean profiles appear shifted downward by ∼1 km, introducing a difference of about 10% with POAM III and about 25% with ozonesonde profiles between 15 km and 32 km. This study demonstrates that outside the April–July 2002 period, the OSIRIS ozone profiles agree well with coincident ozonesonde and POAM III ozone profiles and make a valuable addition to the international ozone database available for research into global ozone change.

Contribution of solar UV radiation to the observed ozone variations during the 21st and 22nd solar cycles

A two-dimensional dynamical radiative-photochemical model of the ozonosphere including aerosol physics is used to examine the changes of the Earth's ozone layer occurred during the 21st and 22nd solar cycles. The calculated global total ozone changes in the latitude range 60°S—60°N caused by 11-year variation of solar UV radiation, volcanic eruptions, and anthropogenic atmospheric pollution containing CO 2, CH 4, N 2O and chlorine and bromine species are in a rather good agreement with the observed global ozone trend. The calculations show that the anthropogenic pollution of the atmosphere is a main reason of the ozone depletion observed during the last two solar cycles. However, the 11-year solar UV variation as well as volcanic eruptions of El Chichon and Mt. Pinatubo also gave a significant contribution to the observed global ozone changes.

Chlorofluorocarbons and ozone.

Chlorofluorocarbons and ozone.

A new self‐calibration method applied to TOMS and SBUV backscattered ultraviolet data to determine long‐term global ozone change

The currently archived (1989) total ozone mapping spectrometer (TOMS) and solar backscattered ultraviolet (SBUV) total ozone data (version 5) show a global average decrease of about 9.0% from November 1978 to November 1988. This large decrease disagrees with an approximate 3.5% decrease estimated from the ground‐based Dobson network. The primary source of disagreement was found to arise from an overestimate of reflectivity change and its incorrect wavelengths dependence for the diffuser plate used when measuring solar irradiance. Both of these factors have led to an overestimate of the rate of atmospheric ozone depletion by SBUV and TOMS. For total ozone measured by TOMS, a means has been found to use the measured radiance‐irradiance ratio from several wavelengths pairs to construct an internally self consistent calibration. The method uses the wavelength dependence of the sensitivity to calibration errors and the requirement that albedo ratios for each wavelength pair yield the same total ozone amounts. Smaller errors in determining spacecraft attitude, synchronization problems with the photon counting electronics, and sea glint contamination of boundary reflectivity data have been corrected or minimized. New climatological low‐ozone profiles have been incorporated into the TOMS algorithm that are appropriate for Antarctic ozone hole conditions and other low ozone cases. The combined corrections have led to a new determination of the global average total ozone trend (version 6) as a 2.9±1.3% decrease over 11 years (October 1978 to November 1989). Version 6 data are shown to be in agreement within error limits with the average of 39 ground‐based Dobson stations and with the world standard Dobson spectrometer 83 at Mauna Loa, Hawaii. The global average ozone trend from version 6 data shows the presence of varying short‐period trends (1979 to 1983, −0.33%/yr; 1983 to 1986, −0.91% yr, and 1986 to 1990, +0.16%/yr) that are partially masked in the original version 5 trends.

Long‐term changes in the total ozone mapping spectrometer relative to world primary standard Dobson spectrometer 83

We have examined the stability of the calibration of the Nimbus 7 solar backscatter ultraviolet (SBUV) and total ozone mapping spectrometer (TOMS) instruments by comparing their ozone measurements with those made by a single, very stable Dobson instrument: the world primary standard Dobson spectrometer number 83. Measurements of ozone made with instrument 83 at Mauna Loa observatory in eight summers between 1979 and 1989 were compared with coincident TOMS ozone measurements. The comparison shows that relative to instrument 83, ozone measured by TOMS (and SBUV) was stable between 1979 and approximately 1983, had decreased by 3% by 1986, and had decreased by almost 7% by 1989. A similar time dependence is seen when data from an ensemble of 39 Dobson stations throughout the world is compared with TOMS over the period 1979–1987. The most likely reason for the relative drift is that the diffuser plate used by both SBUV and TOMS to measure solar flux has suffered an uncorrected wavelength dependent degradation, with most of the degradation occurring after 1983. The recently released version 6 TOMS data, corrected using the internal “pair justification” technique, show almost no drift relative to Dobson instrument 83. We conclude from these comparisons that accurate measurements of long‐term global ozone change will require a coherent system incorporating both ground based and satellite based ozone measurements.

Ozone reduction in the 1980's: A model simulation of anthropogenic and solar perturbations

An interpretation of global ozone changes deduced from satellite data obtained since 1979 is presented, based on two‐dimensional model simulations. The study shows that a depletion in total ozone of the order of 2 percent and a reduction in ozone density near 40 km of 7 to 12 percent over the 1979–1986 period are consistent with the observed increase in trace gas densities (chlorofluorocarbons, methane, nitrous oxide, carbon dioxide) and the simultaneous decrease in solar activity during this period. The model also suggests that ozone variations of solar and anthropogenic origins between 1979 and 1986 were of similar magnitude but that the ozone response to trace gas emissions increases substantially with latitude while the solar signal in ozone is present lower in the atmosphere and is nearly independent of latitude.

Quasi-Biennial and Other Long-Period Variations in the Solar Semidiurnal Barometric Oscillation: Observations, Theory and Possible Application to the Problem of Monitoring Changes in Global Ozone

Abstract A 21-year record of monthly mean determinations of the solar semidiurnal surface pressure oscillation [S2(p) at Batavia (6.2°S) was analyzed to detect long-period variability. When the S2(p) determination were resolved into components which peak at local midnight (and noon) and 0900 (and 2100) local solar time, considerable evidence was found for a quasi-biennial variation in the 0900 component (but not in the midnight component). It is shown that this is consistent with the expected response of S2(p) to the familiar quasi-biennial oscillation of the tropical stratosphere. Also apparent in the record is a very long term trend in S2(p). It is suggested that this way be an indication of a similar trend in stratospheric ozone, and the possibility of using the surface pressure oscillation in monitoring long-term changes in atmospheric ozone is discussed.

Analyzing worldwide total ozone for trends

Total ozone data are statistically analyzed to estimate the trend detection capability which would provide early warning of ozone depletion. Based on a worldwide sample of nine stations, an abnormal global ozone change of 0.26% per year persisting over 6 years would be judged statistically significant, if it were to occur and could not be explained by historical patterns. A resulting 1.56% early warning can limit maximum reversible depletion to 2.3%, if the cause were due to chlorofluoromethanes FC‐11 and FC‐12. The analysis shows no evidence of an abnormal global trend persisting in the 1970's. The potential exists for detecting even smaller changes by using data from all the current land‐based stations and satellites.