Ozone Deficiency Research Articles

Formation of Optical Fiber Preform Using Octamethylcyclotetrasiloxane

There are various manufacturing processes for pure SiO2 that is used as abrasives, chemicals, filters, and glasses, and in metallurgy and optical industries. In the optical fiber industry, to produce SiO2 preform, SiCl4 is utilized as a raw material. However, the combustion reaction of SiCl4 has caused critical environmental issues, such as ozone deficiency by chlorine compounds, the greenhouse effect by carbon dioxide and corrosive gas such as hydrochloric acid. Thus, finding an alternative source that does not have those environmental issues is important for the future. Octamethylcyclotetrasiloxane (OMCTS or D4) as a chlorine free source is recently promising candidate for the SiO2 preform formation. In this study, we first conducted a vaporizer design to vaporize the OMCTS. The vaporizer for the OMCTS vaporization was produced on the basis of the results of the vaporizer design. The size of the primary particle of the SiO2 formed by OMCTS was less than 100 nm. X-ray diffraction patterns of the SiO2 indicated an amorphous phase. Fourier-transform infrared spectroscopy analysis revealed the Si-O-Si bond without the -OH group.

Variability of sunspot cycle QBO and total ozone over high altitude western Himalayan regions

Long-term trend of total column ozone at high altitude region in Ladakh is studied, using a total ozone mapping spectrometer and an ozone monitoring instrument during 1979–2008. In the region, total ozone exhibits seasonality with maximum in spring and minimum in autumn. The decreasing trend of total ozone was found as −2.51±0.45% per decade with 95% confidence level in the region. Ozone deficiency in the Ladakh region is strongest (−33.9 DU at Hanle) in May and weakest (−11.5 DU at Hanle) in January–February. In the study, the solar maximum in 1990 is in phase with ozone maximum, while ozone variation lags in phase with the 1980 and 2000 solar maxima. However, a significant correlation between total ozone and sunspot number is achieved in the westerly phase of quasi-biennial oscillation during spring season. Decreasing trend of ozone in the region is correlating well with the cooling rate in the lower stratosphere.

Characteristics of the ozone decline over both hemispheres

The ozone decline in both hemispheres accelerated up to the 1990s. A number of interesting facts are presented that use objective characteristics, such as ozone mass deficiencies (O3MD) from the pre-1976 averages. In the mid-1990s the major decline in the lower stratosphere was better understood and the essential role of the stratospheric temperature and dynamics affecting the Arctic ozone decline was confirmed. In 1993 and 1995 in the northern latitudes (>35°N) the cumulative winter–spring O3MD was surpassing the deficiencies over Antarctica for the corresponding season. Total ozone deficiencies of 4–6% from pre-1976 averages continue to be observed over extra-tropical latitudes. There is no decline in the tropics only (25°N–25°S). The decline is much stronger in winter–spring than in the summer season and is very much influenced by the meteorological conditions at nearly equal concentrations of ozone depleting substances. The largest spring O3MD over Antarctica was in 2006; the intensity of the loss per unit surface within <220 DU area increased during the past decade and there are no signs of reduction of the ozone losses there.

Middle atmospheric O3, CO, N2O, HNO3, and temperature profiles during the warm Arctic winter 2001–2002

Ground‐based measurements of stratospheric constituents were carried out from Thule Air Base, Greenland (76.5°N, 68.7°W), during the winters of 2001–2002 and 2002–2003, involving operation of a millimeter‐wave spectrometer (GBMS) and a lidar system. This work focuses on the GBMS retrievals of stratospheric O3, CO, N2O, and HNO3, and on lidar stratospheric temperature data obtained during the first of the two winter campaigns, from mid‐January to early March 2002. For the Arctic lower stratosphere, the winter 2001–2002 is one of the warmest winters on record. During a large fraction of the winter, the vortex was weakened by the influence of the Aleutian high, with low ozone concentrations and high temperatures observed by GBMS and lidar above ∼27 km during the second half of February and in early March. At 900 K (∼32 km altitude), the low ozone concentrations observed by GBMS in the Aleutian high are shown to be well correlated to low solar exposure. Throughout the winter, PSCs were rarely observed by POAM III, and the last detection was recorded on 17 January. During the lidar and GBMS observing period that followed, stratospheric temperatures remained above the threshold for PSCs formation throughout the vortex. Nonetheless, using correlations between GBMS O3 and N2O mixing ratios, in early February a large ozone deficiency owing to local ozone loss is noted inside the vortex. GBMS O3‐N2O correlations suggest that isentropic transport brought a O3 deficit also to regions near the vortex edge, where transport most likely mimicked local ozone loss.

Characteristics of episodes with extremely low ozone values in the northern middle latitudes 1957−2000

Abstract. A number of episodes are observed when the total ozone for 2 to 3 days has fallen below 220 matm-cm in the northern mid- and polar latitudes in autumn. The occurrences of such episodes represent ozone deviations of about one-third from the pre-1976 Oct-Nov-Dec monthly mean! By using primarily quality checked Dobson data, a clear identification was made of more than three dozen short spells with extremely low ozone in the 1957–1978 period. In the following twenty-two years (1979–2000), using mainly TOMS data, one can identify ~ 46 cases with ozone values falling below 220 matm-cm for longer than 1 day, with each time over an area greater than 500,000 km2 . The Ozone Mass Deficiency (O3MD) from the pre-1976 average ozone values over the affected area was ~2.8 Mt per day, i.e. four to seven times greater than it would be, assuming only a long-term trend in the Oct-Nov-Dec period. The Extremely Low Ozone (ELO3) events on the day of their appearance over the N. Atlantic/European region contribute to the O3MD by representing 16% of the deficiency due to the Oct-Nov trend in the entire 40–65° N latitudinal belt. The O3MD of the greater pool with low ozone (here taken as &lt;260 matm-cm) surrounding the area of the lowest events could contribute on the day of their appearance in Oct-Nov up to 60% and in December, ~30% to the deficiency due to the trend over the entire 40–65° N belt. Analysis of synoptic charts, supported by a backward trajectory on the isentropic surfaces 350 and 380 K, shows that in most of the events, subtropical air masses with low ozone content were transported from the Atlantic toward the UK, Scandinavia, and in many cases, further to the western sub-polar regions of Russia. This transport was sometimes combined with upward motions above a tropospheric anticyclone which lifted low ozone mixing ratios to higher altitudes. The ELO3 events cause a significant deficiency above the tropopause where, in general, the subtropical air is injected. In fact, the overall amount of ozone is not depleted, but redistributed on the hemispheric scale. Review of low ozone events, defined as days with negative deviations from the pre-1976 averages greater than 25% show, in general, similar origin. The seasonally averaged area with ELO3 and the associated O3MD, as well as for the cases with deviations &gt; –25%, has increased during the 1990s, which could be an indication of stronger and/or more frequent subtropical air intrusions. Their occurrences could contribute noticeably to the ozone deficiency of the middle latitude ozone during the days of ELO3 appearances; however, their contribution to the long-term trend of the ozone seasonal decline is of the order of ~10%.Key words. Atmospheric composition and structure (middle atmosphere - composition and chemistry) Meteorology and atmospheric dynamics (middle atmosphere dynamics)

A global model tool for three‐dimensional multiyear stratospheric chemistry simulations: Model description and first results

The paper presents a new global modeling tool, Stratospheric Chemical Transport Model 2. It has been developed for effective three‐dimensional multiyear stratospheric chemistry studies, featuring an extensive chemistry scheme, heterogeneous processing on sulfate aerosols, and some polar stratospheric cloud processes. The transport algorithm maintains sub‐grid‐scale distributions and connects vertically the stratospheric layers, even in a coarse vertical grid. The model has been integrated for 49 months, recycling 1 year of precalculated transport from a middle atmosphere general circulation model. One year of daily National Centers for Environmental Prediction global analyses are used as temperatures. Diurnal cycles of photolysis rates are recalculated every 7 days to give interaction with ozone changes. The model is able to describe most of the geographical and seasonal ozone variability and the meridional distributions of ozone, reactive nitrogen, chlorine, and bromine. Stratospheric diurnal cycles for nitrogen, hydrogen, chlorine, and bromine species are captured in detail. The upper stratosphere ozone deficiency, typical to models, is large. Its sensitivity to different ways of tuning are explored. Midlatitude, rather than polar, wintertime processes have so far been the focus in this model tool. The present transport and grid resolution are not suited for realistic simulations at high latitudes. As there is only a limited inclusion of polar stratospheric cloud (PSC) microphysics, chemical processing in the cold polar lower stratosphere also cannot be well simulated. For example, the Antarctic ozone hole is not simulated, but the modeled chemistry should be suitable for warm Arctic winters when type II PSCs and particle sedimentation do not occur.

Characteristics of the ozone decline in the northern polar and middle latitudes during the winter-spring

The total ozone decline during the past twenty years, especially strong during the winter-spring season poleward from 50° N, is well established with known average trends of 5–7% per decade. This study presents a number of additional characteristics such as ozone-mass deficiency (O3MD) from the pre- 1976 base average, and areal extent with negative deviations greater than∼2 and∼3δ. Gridded satellite data combined with ground-based total ozone maps, permit calculations of daily and regional ozone deficiencies from the anthropogenically undisturbed average ozone levels of the 1960s and early 1970s. Then the quantity of the O3MD and the changes in surface area, with deficiencies larger than-10 and-15% are integrated for the 1 January to 15 April period for each of the last 20 years, and compared. In addition, the polar vortex extent during the last 10 years is determined using the PV at 475°K. The quantity of the O3MD within the sunlit part of the vortex is shown to contribute from∼15 to 35% of the overall ozone deficiency within the-10% contours over the area 35–90°N. The ozone deficiency, integrated for the first 105 days of each year, has increased dramatically from ∼2,800Mt in the early 1980s to∼7,800Mt in the 1990s, exceeded 12,000Mt in the winter-springs of 1993 and 1995. The latter quantity is comparable with the average O3MD over the same Southern latitudes in the last ten austral springs. During the 1990s over the 35–90° latitudes the average ozone deficiency in the Southern hemisphere belt is less than over the Northern hemisphere belt by∼40%. It is known that the main ozone decline is observed in the lower stratosphere and the ozone loss over the Arctic is very sensitive to decreasing stratospheric temperatures; negative 50hPa monthly anomalies greater than 4°C have occurred during 7 of the springs in the last decade, thus possibly facilitating doubling the area with negative ozone deviations greater than-10% in the 1990s to∼5,000.106km2 and nearly tripling the O3MD as stated above. The changes in total eddy heat fluxes as a proxy indicator of the long wave perturbations are positively correlated with the ozone deficiency in the 45–75°N. The strong anticorrelation between the ozone deficiency in the region>55° N. versus the 35–50° N belt is discussed in relation to possible transport of air masses with low ozone from the sub-tropics, which in some years are the dominant reason for the observed ozone deficiency.

On the daily maximum UV-B doses during the significant ozone deficiencies in the transition seasons of 1992/93

The daily maximum UV-B dose rates during the significant ozone anomalies in October 1992 and March 1993 are calculated relative to the normal conditions of the period from 1979 to 1990. Gridded Total Ozone Mapping Spectrometer data have been used to determine the days with ozone deficiencies below the 2σ confidence level. For these days maps of maximum daily UV-B dose rates during these extreme ozone conditions show that UV-B dose rates increased from 10% to 50% at high latitudes. These changes compare well with observations at the Laboratory of Atmospheric Physics, of the Aristotle University of Thessaloniki, Greece and they provide an independent quality assurance and control of the accuracy of coarser model calculations under clear sky conditions. Our analysis shows that the largest increases in the UV-B dose rates during the extreme ozone deficiencies studied are confined to 10°N–40°N in March 1993 and to 10°S to 70°S in October 1992.

Temporal and spatial variation of dominant pelagic Copepoda (Crustacea) in the Weddell Sea (Southern Ocean) 1929 to 1993

The abundances of four dominant Antarctic copepod species, Metridia gerlachei, Rhincalanus gigas, Calanoides acutus and Calanus propinquus, were examined in the Southern Ocean in a combination of a literature review, analysis of museum samples and field sampling. The data were analysed for spatial and temporal variations. The data included in the analysis were from the Weddell Sea area in the summertime at periods 1929–1939 and 1989–1993. The results are discussed in the light of environmental changes and their hypothesised and observed consequences in the Southern Ocean: global temperature change, ozone deficiency and cascading trophic interactions. Combining all these hypothetical effects our null hypothesis was that there were no consistent long-term changes in the abundance of dominant pelagic Copepoda. The null hypothesis was rejected, since several taxons did show statistically significant long-term changes in abundance. The changes were not uniform however. The numbers of adults and juveniles of Calanus propinquus increased significantly between the periods studied. Adult stages of Calanoides acutus were the only taxon decreasing in abundance, in concert with the cascading trophic interactions theory. Latitudinally, only Metridia gerlachei showed a significant increase from north to south. Longitudinally, the abundances of Calanus propinquus juveniles and both adults and juveniles of Rhincalanus gigas increased from west to east. There were no significant variations between day and night samples. Interannual changes were statistically significant in juvenile stages of all the species and in adults of Calanus propinquus. We conclude that no uniform and consistent abundance changes could be observed in the pelagic Copepoda of the Weddell Sea that could be connected to major environmental changes, expected to affect the whole planktonic ecosystem of the Southern Ocean. Significant changes in some of the species studied show that the pelagic ecosystem is not in a steady state, but in addition to interannual changes, there are also major fluctuations extending over decades.

The role of stratospheric minor warmings in producing the total ozone deficiencies over Europe in 1992 and 1993

During 1992 and 1993, record low total ozone values were observed over the middle and high northern latitudes. The ozone data from the long-operating station at Belsk, Poland, have been used to examine their departures from climatological behaviour in 1992 and 1993. It seems that not only do the exceptionally low ozone amounts recorded over the northern mid-latitudes need an explanation but also their occurrence for two years in a row. One of the possible mechanisms which may be responsible for this event is suggested to be connected with the occurrence of stratospheric minor warmings. They occur without a breakdown of the polar vortex but only with the displacement of very cold air towards lower latitudes (as in January 1992 and February 1993). It is known that air masses in the polar vortex have been chemically disturbed and, when they arrive over the sunlit middle latitudes, chemical destruction of ozone is likely to occur. During the periods under study, the strongest negative total ozone deviations correspond to strong negative temperature deviations at 30 hPa and to large potential vorticity values; this points to the presence over Europe of air masses of polar vortex origin. It has been shown that the characteristics of mid-winter stratospheric warmings and the interannual variability of winter-spring total ozone averages at Belsk are associated with each other.

Seasonal variation and trends of Toms ozone over Tibet

Using Nimbus‐7 Total Ozone Mapping Spectrometer (TOMS) data, this article discusses the seasonal variation in total ozone over the Tibetan Plateau. In addition, total ozone trends over this region are revealed by linear regression analysis. Low ozone concentrations are found over the large scale topographies of the Tibetan Plateau, the Rocky Mountains, and the Andes Mountains. The phenomenon is the strongest over Tibet. Total ozone in Tibet is lowest in October and highest in March. However, relative to zonal mean total ozone, largest ozone deficiency over Tibet occurs in May, while smallest deficiency occurs during November–January months. The ozone deficiencies are negatively correlated to the heat flux from the surface to the air in Tibet, with correlation coefficient −0.97. The ozone trend over Tibet, deduced from TOMS 1978–1991 year‐round data, is −0.79±0.82 DU/Year (−2.7±2.8 percent/decade), with the monthly trends ranging from −0.17 DU/year (−0.6 percent/decade) to −1.79 DU/year (6.0 percent/decade).

Further studies on possible volcanic signal to the ozone layer

This paper provides a new look at the spatial and temporal distribution of monthly mean residuals of the global ozone field following the two large volcanic eruptions of El Chichon and Pinatubo. The residuals have been calculated after careful removal of the components of known oscillations from the monthly mean total ozone records. The removal eliminated not only the well‐established Quasi Biennial Oscillation but also the robust pattern of all El Nino/Southern Oscillation events active during the period of study. These residuals are composed by a “climatic noise” term plus a possible volcanic signal whose amplitude is in some agreement with model calculations particularly over low and middle latitudes following the recent Pinatubo eruption. However, this analysis shows no ozone deficiency following El Chichon over the southern hemisphere and this result can be explained by the prevailing winds in the lower stratosphere in the post‐El Chichon period as described in the text. Quantitatively speaking, the magnitude of the observed ozone deficiency which can be attributed to the volcanic effect is smaller than reported earlier either from theory or observations, and ranges between 2 and 4% at the equatorial latitudes up to about 5% over the middle and high latitudes, including the noise term, and lasting for a period of months after the eruption. These deficiencies are also larger than the anticipated error caused by the aerosol‐contaminated radiances, as reported by other scientists. The present results, although not precluding a transient volcanic component following large volcanic eruptions in the ozone records, do show, however, that our understanding of the physical mechanisms involved is probably still incomplete.

Total ozone changes over Eurasia since 1973 based on reevaluated filter ozonometer data

Since the early 1960s, on the vast territory of the former USSR, 45 stations have been in continuous operation, utilizing the broadband filter M‐83 ozonometer. The quality of the ozone data during the first decade was unsatisfactory. After 1972 an improved version of the ozonometer was introduced together with improved quality control practices, including methodology of observations. The more reliable data of 1973 through March 1994 have been rigorously reexamined by applying variability analysis, comparison with lower‐stratosphere temperatures and/or nearby Dobson stations, and overpassing TOMS for identifying concurrence or discrepancies. These control procedures together with the information on instrument relocation and calibrations made it possible to reevaluate the record of all 45 stations. The accuracy of the improved ozonometer data is about 3% for direct Sun measurements and ∼5% for zenith sky observations; although not so good as that of the Dobson, in the long run it provides consistent ozone data sets. This data set is now made available to the World Ozone Data Center (WO3DC), Toronto. Thus for the first time, based on a 21‐year long record, information is deduced on the differences in the ozone annual cycle between Eastern Siberia and the European part, on the strong appearance of quasi‐biennial oscillation (QBO) signals especially pronounced as ozone deficiency during the western phase of the QBO, on the ozone variability, and on the long‐term changes over the huge territory from Central Europe to the Far East. The specifics of the ozone changes considered in concurrence with the prevailing general stratospheric circulation conditions permitted us to distinguish four broad regions with consistent ozone regimes. The appearance of the strongest northern hemisphere ozone maximum and a monthly mean of ∼470 matm cm over Siberia during winter‐spring, compared with ∼400 matm cm over Europe, the occurrence of the ozone annual minimums as early as August over Eastern Siberia, compared with October over the European part, was established and is probably related to the specifics of the atmospheric circulation patterns. The long‐term ozone changes are considered in relation to the stratospheric temperature at 100‐hPa. For each deviation from the monthly normal temperature by 1°C, there is a corresponding change by the same sign 5–6 matm cm in the monthly ozone deviations. The calculated long‐term ozone trends for 1973 through March 1994 (given in percent per decade ±2σ) are as follows: European part, −3.6±0.8; Central Asia, −2.0±0.6; Western Siberia, −3.5±0.8; and Eastern Siberia ‐ Far East, −3.2±0.8. They show a steady ozone decline similar to that deduced from the Dobson stations at the same latitudes. The decline during the past 15 years is stronger and, in general, concurs with Total Ozone Mapping Spectrometer (TOMS) trends which are, however, slightly more negative.

Ozone deficiency and deficit recovery time at Ispra in 1993 with respect to 1992

Total ozone values measured at Ispra, Italy (45048′ latitude, −8037′ longitude) by a Brewer station during 1992 and 1993 have been compared. The time required in 1993 by ozone to recover the level of the previous year lasted up to the end of July, while for 1992 the recovery to reference ozone values obtained by averaging thirty years of data (1957–1986) taken at Arosa (Switzerland) was about three months shorter. For the first six months of 1993, a mean ozone deficit of the order of 4% with respect to the value for the same period of 1992 has been calculated. An analysis of the UV data taken together with ozone confirmed the anomalous behaviour of ozone in the first half-year of 1993.

Record low total ozone during northern winters of 1992 and 1993

The last two winter‐spring seasons (DJFM) distinguished themselves by being with the lowest ever total ozone over all three continental size regions between 45°N and 65°N of North America, Europe and Siberia. The total ozone deficiencies for the entire season over all of the above mentioned regions were about 11% and 13% below the long‐term normal during the two consecutive years (1991/92 and 1992/93 respectively ). This helped to pull down the cumulative ozone decline since the winter‐spring of 1969/70 to be about 14% in the latitude belt of the 45°N–65°N. Frequencies of days with ozone values deviating below the long‐term mean by more than 2σ have been ten times higher than their 35‐year average. There are evidences deduced from trajectories on potential temperature surfaces that transport of poor in ozone air masses forced in addition by vertical motions, could account for a number of the extreme cases. There is also evidence that cold air, known to have excess ClO content, has moved over the sun lighted latitudes on many occasions, when chemical ozone destruction could have been favored. These ozone deficiencies do not have similar rates of decline and did not reach even close to the extreme low values regularly observed during the Antarctic‐spring ozone hole phenomena.

Stratospheric ozone depletion at northern midlatitudes after major volcanic eruptions

During winter 1982/83 and in early 1985, abnormal ozone deficiencies in the stratosphere were recorded at northern midlatitude stations. Ozone variations measured by ozonesondes at Hohenpeissenberg are analysed with respect to dynamic transport variations related to the quasibiennial oscillation (QBO). After the elimination of seasonal fluctuations, long-term trends and average QBO related variations, ozone time series are compared to particle surface area densities derived from lidar measurements of the stratospheric aerosol layer at Garmisch-Partenkirchen. The two stations are only 37 km apart. The analysis reveals that the 1985 ozone minimum is a transport effect, as well as most of the 1982/83 minimum. But at 17 to 20 km in 1982/83, 30 to 40% of the ozone deficiency is most probably related to the aerosol perturbation of the lower stratosphere following the April 1982 eruption of the Mexican volcano El Chichon.

Deficiency in model ozone in lower thermosphere and excitation of 567.7 nm in nightglow

The ozone source O 2 ( 5Π g ) + O 2 → O 3 + O is investigated. It may remove Alien's model ozone deficiency in the lower thermosphere. If it does O 2 ( 5Π g) could not be the precursor to the green line in the nightglow which would leave O 2 (c 1∑ u −2) as the only possible precursor to this line.

The 1979‐1985 ozone decline in the Antarctic as reflected in ground based observations

Since 1979, from late September to the end of November, the total ozone over the southern polar region has declined by up to 30%, compared with the ozone average for 1957‐78. During the rest of the year there are no indications of a major decline. Neither are there significant changes in the middle latitudes surrounding Antarctica except those related to the QBO. More than 85% of the entire ozone deficiency is observed between 10 and 24 km. The rapid ozone and temperature increase in spring usually occurs in mid October and shows a 2 month lag, compared to the Arctic. The increase is related to the time of the breakdown of the winter stratospheric polar vortex. During the last six years the breakdown has occurred around mid‐November, extending the period with circumpolar circulation by 3‐4 weeks. It is suggested that weak upward motions within the vortex, in the order of 0.1 cm sec−1 during September and October, could cause part of the ozone decline.