Ozone Anomalies Research Articles

Quasi-Biennial and Subbiennial Variations of Stratospheric Trace Constituents Derived from HALOE Observations

Interannual variability of trace constituents in the stratosphere is examined using methane, water vapor, and ozone data from the Halogen Occultation Experiment aboard the Upper Atmosphere Research Satellitein 1992‐ 99. Application of rotated principal component analysis to the dataset reveals dominant modes of variability consisting of annual, semiannual, and quasi-biennial oscillations (QBOs), together with ‘‘subbiennial’’ variations evidently due to nonlinear interaction between the annual cycle and QBO. The structure of quasi-biennial variability is approximately symmetric about the equator, while subbiennial variability, with certain exceptions, is approximately antisymmetric and confined mostly to the subtropics. The vertical structure and downward propagation of the ozone QBO at the equator is described by a pair of symmetric EOFs having separate amplitude maxima in the lower and upper stratosphere. A second pair of EOFs explains the seasonal dependence of subtropical ozone anomalies. For each tracer, the subtropical anomaly is larger in the Northern Hemisphere. A novel ‘‘phase diagram’’ illustrates the joint seasonal and QBO dependence of tracer anomalies. A pair of principal components are used to define the phase of the dynamical QBO. When plotted against the phase of the annual cycle, the QBO follows a diagonal trajectory with regular phase progression except for an occasional slowing of easterly shear-zone descent near 50 hPa. Tracer principal components of symmetric and antisymmetric EOFs, plotted along this trajectory, display the distinct signatures of quasi-biennial and subbiennial variation. Tracer anomalies reconstructed using an idealized representation of QBO and subbiennial harmonics display the seasonal synchronization and decadal modulation characteristic of QBO‐annual cycle interaction.

Solar UV‐B irradiance and total ozone in Italy: Fluctuations and trends

Solar UV irradiance spectra (290–325 nm) together with daily total ozone column observations have been collected since 1992 by means of Brewer spectrophotometers at two Italian stations (Rome and Ispra). The available Brewer irradiance data, recorded around noon and at fixed solar zenith angles, together with the output of a radiative transfer model (the STAR model) are presented and analyzed. The Brewer irradiance measurements and total ozone fluctuations and anomalies are investigated, pointing out the correlation between the high‐frequency O3 components and irradiance at 305 nm. In addition, the total ozone long time series of Arosa (170 km apart from Ispra) and Vigna di Valle (very close to Rome) are analyzed to illustrate evidence of temporal variations and a possible trend.

Surface UV radiation over Australia, 1979–1992: Effects of ozone and cloud cover changes on variations of UV radiation

Time series of daily erythemal ultraviolet radiation (UVR) exposure, ozone, and cloud cover were analyzed over the Australian continent using data sets from the NASA Total Ozone Mapping Spectrometer (TOMS) from 1979–1992. The TOMS UVR exposures showed good agreement with data from surface observations. Using a relationship derived from comparisons of the TOMS partial cloud reflectivities with surface cloud cover observations, the TOMS reflectivities were converted into estimates of cloud cover for several Australian regions. It was shown that the deseasonalized time series of UVR exposures can be statistically described as a linear function of ozone and cloud cover anomalies. Results of a trend analysis indicated statistically significant increases in UVR exposures of 10% decade−1 in the summer months in the tropics. These were associated with a simultaneous depletion of ozone and a decrease in cloud cover. Midlatitudinal regions showed no significant trends of UVR. It was found that variations of ozone and UVR over Australia were significantly influenced by the quasi‐biennial oscillation (QBO). An increase in zonal wind strength of 20 m s−1 was correlative with reductions of ozone of 1.7% and enhancements of UVR exposures of 2.2%. An increase in solar radio flux of 100×10−22 W m−2 (Hz)−1 was associated with significant reductions of UVR of 5–10% in the tropical and subtropical regions in summer. The results suggested that enhancements in summer UVR exposures of about 10–20% above the climatological average might be expected in years in which the QBO is in its westerly phase and the solar cycle is at its minimum.

The role of dynamics in total ozone deviations from their long-term mean over the Northern Hemisphere

Abstract. Total ozone anomalies (deviation from the long-term mean) are created by anomalous circulation patterns. The dynamically produced ozone anomalies can be estimated from known circulation parameters in the layer between the tropopause and the middle stratosphere by means of statistics. Satellite observations of ozone anomalies can be compared with those expected from dynamics. Residual negative anomalies may be due to chemical ozone destruction. The statistics are derived from a 14 year data set of TOMS (Total Ozone Mapping Spectrometer January 1979-Dec. 1992) and corresponding 300 hPa geopotential (for the tropopause height) together with 30 hPa temperature (for stratospheric waves) at 60°N. The correlation coefficient for the linear multiple regression between total ozone (dependent variable) and the dynamical parameters (independent variables) is 0.88 for the zonal deviations in the winter of the Northern Hemisphere. Zonal means are also significantly dependent on circulation parameters, besides showing the known negative trend function of total ozone observed by TOMS. The significant linear trend for 60°N is \\sim3 DU/year in the winter months taking into account the dependence on the dynamics between the tropopause region and the mid-stratosphere. The highest correlation coefficient for the monthly mean total ozone anomalies is reached in November with 0.94.Key words. Atmospheric composition and structure (middle atmosphere · composition and chemistry) · Meteorology and atmospheric dynamics (middle atmosphere dynamics).

A comprehensive optical investigation of processes of transformation of the ozonosphere above Tomsk

The results are given on experimental optical research into variations and peculiarities of the time dependence of the total ozone content (TOC) and the influence of an eruption of the Pinatubo Volcano on the stratospheric ozone layer, as well as observations of local negative ozone anomalies and polar stratospheric clouds (PSCs), obtained during lidar and spectrophotometric measurements at the Siberian Lidar Station (56°.5 N, 85°.0 E). It is shown that normal and anomalous deviations in TOC are due to atmospheric dynamics and depend on the amount of anomaly in the atmospheric processes themselves. Under the conditions of considerable loading of the stratosphere with volcanogenic aerosol, a substantial inverse relationship between aerosol and ozone contents is observed. The formation of PSCs and a local TOC decrease correspond to an anomalous thermodynamic state of the troposphere and lower stratosphere.

Effects of the quasi‐biennial oscillation on the zonally averaged transport of tracers

The influence of the quasi‐biennial oscillation (QBO) on the transport of long‐lived tracers out of the tropics and the mechanism responsible for the QBO in subtropical ozone and its dependence on the seasonal cycle are examined with a two‐dimensional model. The modeled QBO induces a meridional circulation which modulates transport of long‐lived tracers out of the tropics. The induced circulation also produces a QBO in ozone in the subtropics by advection of ozone out of the tropics and down from higher altitudes. In agreement with observations, the subtropical anomalies in ozone are greatest in the winter season. This seasonal synchronization of the subtropical anomalies occurs because the induced circulation is stronger always in the winter hemisphere as a result of nonlinear momentum advection in the tropics and subtropics. Meridional transport in the model is enhanced by the QBO through an “upper” and a “lower” transport regime, in agreement with the analysis by Hitchman et al. [1994]. When there are descending westerly winds in the tropics in the model, transport out of the tropics is enhanced in the lower stratosphere. When there are descending easterlies, transport out of the tropics is enhanced in the middle stratosphere. This modulation of transport out of the tropics significantly influences the stratospheric distribution of long‐lived tracers. Depending on the phase of the QBO, mixing ratio surfaces of long‐lived tracers (such as N2O) in the extratropics can be displaced poleward by more than 10°.

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.

Principal modes of the total ozone on the Southern Oscillation timescale and related temperature variations

Total ozone and associated temperature variations on the Southern Oscillation timescale have been investigated using monthly total ozone mapping spectrometer and temperature data for the latitudinal domain between 70°N and 70°S and from 1979 to 1991. The first two modes for total ozone describe the anomalous total ozone patterns associated with the extremes in the Southern Oscillation. The first mode has the largest loadings in the southern hemisphere (SH) subtropics and midlatitudes with an east‐west dipole in antiphase with a tropical east‐west dipole. The second mode has its largest loadings in the tropics with an east‐west dipolar pattern. These modes are intimately related to variations in the mean temperature in the lower stratosphere, and this relation is such that the total ozone and mean temperature anomalies are positively correlated. The tropospheric temperature patterns are confined in the tropics, where temperature and total ozone anomalies are negatively correlated. The tropical temperature and total ozone variations are driven by modulations in the tropical convection associated with the Southern Oscillation. The Southern Oscillation signals in the stratospheric temperature and in the total ozone are strongest in the SH midlatitudes during the winter‐spring period and precede the extremes in the Southern Oscillation Index (SOI) by a few months. Thus the total ozone index, defined similarly to the SOI, seems to be more appropriate than the SOI to monitor the stratospheric temperature in the extratropics, in particular in the SH middle to high latitudes.

An investigation of dynamical contributions to midlatitude ozone trends in winter

On timescales less than a month, negative (positive) 100 hPa temperature anomalies (deviations from seasonal means) and positive (negative) 100 hPa height anomalies at northern midlatitudes are associated with negative (positive) total ozone anomalies owing to vertical and horizontal advective transport of ozone. We apply linear regression relationships between total ozone and 100 hPa temperature and height together with observed monthly temperature and height anomalies to estimate the component of total ozone variability at northern midlatitudes that results from month‐to‐month differences in advective transport. At 45°N, this empirical method simulates a large part of the observed monthly zonal mean total ozone variability over the period 1979–1991. In order to estimate the advective transport contribution to total ozone trends, we apply a multiple regression statistical model to empirical model time series for latitudes of 10°N to 60°N. These empirical model trends result from long‐term changes in ozone advective transport which are calculated on a month‐to‐month basis. The resulting model trend component at northern midlatitudes in February has a longitude dependence consistent with that of the observed ozone trends and has a latitude dependence that also agrees with that of the observed trends, peaking at midlatitudes and decreasing at higher latitudes. Subtracting the estimated advective contribution from the observed trends yields a residual meridional trend profile that agrees more closely in latitude dependence and amplitude with two‐dimensional stratospheric model estimates.

Changes of the lower stratospheric ozone over Europe and Canada

Ozonesonde measurements from Europe arid Canada for the period 1973–1994, stratified to the height of the tropopause, were analyzed to estimate regional changes in stratospheric ozone. The calculations were performed for 1‐km layers from the actual tropopause up to 30 km and within ±4 km around the tropopause. The long‐term changes in ozone partial pressure are very similar for both regions, and ozone anomalies show many common features. Negative deviations of 15–25 nbar (or 10–20%) are clearly seen in 1976 (at 12–20 km), 1983 (at 17–22 km), 1985 and 1988 (at 18–25 km), 1989 and 1990 (at 12–20 km), and 1992 and 1993 (at 12–23 km). In January‐April 1995, negative deviations of 15–25 nbar (at 12–23 km) were observed again over the two regions, Trend estimations demonstrate that the strongest decline, in units of ozone partial pressure, takes place at 17–20 km over Europe in January‐April and for Canadian stations from March through June. For the period 1973–1994 the decline over both regions is 10–13 nbar per decade (or 5–10% per decade) and is ∼1.5 times larger for the shorter time interval 1979–1994. The estimation of trends as a function of altitude from the actual tropopause level reduces the relative error in the 7 to 13‐km layer by more than one third, which permits better understanding of the ozone changes in these critical altitudes. Using stratified ozone data around the height of the tropopause, the negative stratospheric winter‐spring trends became significant (10–15 nbar per decade or 12–17% per decade) at only 1–2 km above the tropopause.

Pinatubo aerosol and stratospheric ozone reduction: Observations over central Europe

Long‐term observations of ozone profiles at Lindenberg (52.2°N, 14.1°E) and of profiles of the particle surface area concentration at Geesthacht (53.4°N, 10.4°E) are evaluated. Six time series of monthly mean ozone anomalies are formed for layers between 13.5 and 27 km height. The effects of seasonal variation, trend, quasi‐biennial oscillation (QBO), polar vortex, and North Atlantic oscillation (NAO) are eliminated. The residual anomalies indicate aerosol‐induced ozone losses between 10 and 30% in the central part of the Pinatubo layer (15–20 km height) in the winter and spring seasons of 1991–1992 and 1992–1993. Values of the monthly mean particle surface area concentration ranged from 10 to 36 mm2 m−3 during this time period. A correlation analysis, based on mean values of the ozone and aerosol data for the lower, central, and upper part of the Pinatubo layer, indicates a weak positive linear relationship between ozone depletion and surface area in each of the three layers. There is a generally strong influence of the polar vortex strength on the ozone concentration in winter. In the winter of 1992–1993, 10 to 60% of the entire ozone reduction is estimated to be related to the anomalously strong polar cyclone. After the elimination of the vortex‐induced reduction, winter mean sulfate‐related ozone losses of 10 to 20% were associated with winter mean surface area concentrations of 15 to 20 mm2 m−3 for the first two winters after the eruption. The observations are compared with other measurements at northern midlatitudes and with model calculations. In general, a good agreement is found.

Wintertime stratospheric ozone changes over Japan since 1991

Total ozone and ozonesonde data obtained in Sapporo (43°N), Tsukuba (36°N), Kagoshima (32°N), and Naha (26°N) since 1991 were analyzed to study the stratospheric ozone changes over Japan. It was found that sizable total ozone anomalies occurred in the winters of 1992/93 and 1994/95 at the four stations, although the duration and magnitude of the ozone decreases were different between the two periods. Ozone profiles showed increases in ozone concentration above 26 km in the winter of 1991/92 and the most pronounced ozone depletion in the winter of 1992/93 at the four stations. The altitude regions of significant ozone losses in Sapporo, Tsukuba, and Kagoshima in the winter of 1994/95 were higher than those in 1992/93. The latitudinal differences in the degree of ozone losses between 26°N and 43°N since 1991 are presented. The effects of the volcanic aerosol from the Pinatubo eruption and Quasi Biennial Oscillation (QBO) on total ozone are discussed.

On the correlation between tropopause pressure and ozone above central Europe

For a period of twenty years the correlation between local readings of total ozone collected above Hohenpeissenberg are correlated with local measurements of the tropopause pressure above Munich. Regionally averaged values of ozone columns provided by TOMS are additionally correlated with tropopause pressure derived from ECMWF analyses. The correlation coefficient between total ozone and tropopause pressure results to 0.48±0.02 (local data) and 0.55±0.02 (regional mean values). A vertical displacement of the tropopause by one kilometre is associated with an ozone anomaly of 13 Dobson units.

Investigation of the interaction between variations in atmospheric thermal tides and anomalous ozone concentration

This paper discusses the variations of atmospheric semi-diurnal tidal parameters caused by global ozone anomalies of the Antarctic “ozone hole” type and to establish some regularities of their evolution. The analysis of preliminary data showed that the anomalous decrease of ozone concentration in October at high latitudes of the Southern hemisphere results in a simultaneous abrupt drop of the semi-diurnal tidal amplitude values at high latitudes of the lower thermosphere in the Northern hemisphere. Inasmuch as such an abrupt decrease of amplitude values in the lower thermosphere in October is observed from experimental data since 1953 the authors have set up the hypothesis that the Antarctic “ozone hole” had appeared at least not later than this time period.

Observational study of the quasi‐biennial oscillation in ozone

The structures of the quasi‐biennial oscillations (QBOs) in zonal wind, temperature, and layer ozone amounts are investigated using 11.5 years (January 1979 to June 1990) of National Meteorological Center (NMC) global geopotential height data and global ozone data from the solar backscatter ultraviolet spectrometer (SBUV) on Nimbus 7. The QBO signals are isolated by computing lagged correlations between the deseasonalized, detrended variable fields and a reference signal representative of the equatorial QBO. Lagged correlations are calculated for the full time series and for each season separately to determine seasonal effects. The results depict an equatorial zonal wind QBO in good agreement with the observed QBO in ground‐based equatorial zonal wind measurements, although the amplitude of the derived QBO in the NMC data is ∼30% too weak. The vertical extent of the oscillation is significantly higher (2 mbar) than that previously reported. The temperature QBO is consistent with ground‐based observations in the lower stratosphere but weakens with height above ∼50 mbar. The ozone QBO is strong at all levels from 5 mbar into the lower stratosphere. Though the annual average total ozone QBO is quite symmetric about the equator, the oscillation is highly variable from layer to layer. The phase of the ozone QBO near the equator is consistent with that of the zonal wind and temperature in the middle and upper stratosphere, but the vertical resolution of the SBUV data in the lower stratosphere is too low to accurately represent the vertical phase of the ozone QBO in this region. Subtropical temperature and total ozone anomalies are found to be dependent on season.

Boundary layer ozone variations in the eastern United States and their association with meteorological variations: Long‐term variations

Ten years (1981–1990) of Aerometric Information Retrieval System and Southern Oxidant Study ozone data and National Climatic Data Center meteorology data were used to establish statistics on summertime ozone in the eastern two‐thirds of the United States (i.e., the region west of 100 W) and in the SOS region (i.e., the southeastern states), and to study the long‐term variations of the ozone with surface climate parameters. The 10‐year average summertime distribution of the surface ozone was oriented northeast‐southwest, with largest values in the northeast. Gradients extend east to west across the region as expected, but the strongest gradients were directed north‐south and were found in the southern and northern part of the region. A region of high standard deviation (i.e., intersummer variations) was found extending from Indiana‐Michigan eastward to the coast with a center (±10 ppb) over New Jersey‐Connecticut, and in the south, extending from Alabama eastward to the coast (±8 ppb). The centers of large intersummer ozone variation were found in regions characterized by large numbers of anthropogenic sources (Clark, 1980) and by higher‐than‐normal surface temperatures. For the eastern United States, the area‐averaged ozone anomalies ranged from approximately +6 ppb to approximately −2 ppb, with positive anomalies in the summers of 1983 and 1988 only. Highest correlations were noted between the ozone and surface temperature and sky corner, the weakest correlations, with surface pressure and surface winds. Positive surface temperature anomalies are not only indicators of areas where there is high intersummer ozone variability, but also of summers with higher‐than‐normal, area‐averaged ozone.

A Two‐Dimensional Model Study of the QBO Signal in SAGE II NO2 and O3

Calculations of the QBO signal in SAGE II O3 and NO2 data between 1984 and 1991 are presented and have been investigated by using a two‐dimensional model. The isentropic 2D model is a fully interactive radiative‐dynamical‐chemical model in which the eddy fluxes of chemical species are calculated in a consistent manner. The QBO in the model has been forced by relaxing the equatorial zonal wind toward the observations at Singapore allowing the comparison of the model with observations from specific years. The model reproduces the observed vertical structure of the equatorial ozone anomaly with the well‐known transition from dynamical to photochemical control at around 28km. The model also reproduces the observed vertical structure of the SAGE II observed NO2 anomaly. The model studies have shown that it is the QBO modulation of NO2 which is the main cause of QBO signal in O3 above 30km. The model also reproduces the observed latitudinal structure of the QBO signals in O3 and NO2. Due to the differing horizontal distribution of O3 and NOy the ozone signal shows a distinct phase change in the subtropics whereas the NO2 anomaly gives a broader signal.

Coherent variations of monthly mean total ozone and lower stratospheric temperature

Space‐time patterns of correlation between total ozone and lower stratospheric temperature are documented, based on 14 years (1979–1992) of global monthly mean observations. Data are obtained from the total ozone mapping spectrometer (TOMS) and microwave sounding unit (MSU) channel 4, the latter being a weighted mean temperature of the 150‐ to 50‐mbar layer. These data are analyzed (separately) for linear trend, solar cycle, quasi‐biennial oscillation (QBO), and El Niño‐Southern Oscillation (ENSO) variations via linear regression: significant signals are identified for each term, and the corresponding structures in ozone and temperature are found to be highly coherent. The temperature trends derived here show significant cooling of the lower stratosphere over Northern Hemisphere (NH) midlatitudes in winter‐spring and over Antartica in Southern Hemisphere (SH) spring; the overall space‐time patterns are similar to those determined for ozone trends. Interestingly, temperatures do not decrease over SH midlatitudes during midwinter, in spite of large ozone losses. These data furthermore show globally coherent ozone and temperature perturbations associated with both QBO and ENSO variations; a new result here shows large total ozone anomalies in middle‐to‐high latitudes of both hemispheres associated with ENSO events. Residuals from the ozone and temperature time series (defined as the deseasonalized total minus the regression fits) show strong positive correlation in middle‐to‐high latitudes but weak correlations in the tropics. Time periods following the volcanic eruptions of El Chichon and Pinatubo are clearly identified from the coupled signatures of decreased ozone and increased temperature, opposite to the positive ozone‐temperature correlations observed at other times. The ratios of ozone to temperature anomalies derived here show quantitative signatures indicating that either radiative (trend, solar, and QBO) or dynamical (ENSO and residuals) processes are responsible for the strong ozone‐temperature correlations.

Ozonesonde measurements at Hilo, Hawaii following the eruption of Pinatubo

Ozonesonde measurements at Hilo, Hawaii (20°N), after the eruption of Pinatubo in June 1991, are compared to measurements made there from 1985 to 1990 in order to investigate possible volcanic effects. The general nature of the ozone anomalies in 1991–92 can be summarized as lower than normal ozone below about 25 km and higher than normal ozone above. The net result was that total ozone was somewhat lower than average and, during late 1992, was as low as recorded in 1982, following the eruption of El Chichón. Elevated temperatures in the region of the volcanic aerosol layer and upward motion of the aerosol layer were observed at Hilo following the eruption. Although the nature of the perturbed ozone profile may be the result of enhanced upward motion associated with volcanic aerosol particle heating, and the coupling of quasi‐biennial oscillation effects, the persistent nature of the perturbation, still present more than a year after the eruption, is not easily explained.

Multi‐isotope study of ozone: Implications for the heavy ozone anomaly

Laboratory experiments have been performed with O and O2 in their ground electronic states to study the distribution of all possible ozone isotopes formed. Results show that with respect to 48O3 the two symmetric molecules 17O17O17O and 18O18O18O are depleted, in good agreement with standard recombination theory. A large enrichment of about 18% is found in the asymmetric molecule 16O17O18O, while all others carry about 2/3 of that. A comparison with past laboratory and stratospheric ozone isotope measurements leads to the following conclusion: There is a standard enrichment which resides in asymmetric molecules only. It will lead to an enrichment of stratospheric 49O3 and 50O3 of 8 to 9%; this has been actually observed in recent balloon experiments. Occasionally, the enrichments in the stratosphere are larger, reaching 40% at certain altitudes. Only when ozone was formed in an electric discharge process have larger enrichments been measured in laboratory experiments, affecting both symmetric and asymmetric molecules. The results provide an important connection between numerous laboratory studies and stratospheric measurements.