Stratospheric Ozone Concentrations Research Articles

Solar UV radiation measurements in Marambio, Antarctica, during years 2017–2019

Abstract. In March 2017, measurements of downward global irradiance of ultraviolet (UV) radiation were started with a multichannel GUV-2511 radiometer in Marambio, Antarctica (64.23∘ S; 56.62∘ W), by the Finnish Meteorological Institute (FMI) in collaboration with the Servicio Meteorológico Nacional (SMN). These measurements were analysed and the results were compared to previous measurements performed at the same site with the radiometer of the Antarctic NILU-UV network during 2000–2008 and to data from five stations across Antarctica. In 2017/2018 the monthly-average erythemal daily doses from October to January were lower than those averaged over 2000–2008 with differences from 2.3 % to 25.5 %. In 2017/2018 the average daily erythemal dose from September to March was 1.88 kJ m−2, while in 2018/2019 it was 23 % larger (2.37 kJ m−2). Also at several other stations in Antarctica the UV radiation levels in 2017/2018 were below average. The maximum UV indices (UVI) in Marambio were 6.2 and 9.5 in 2017/2018 and 2018/2019, respectively, whereas during years 2000–2008 the maximum was 12. Cloud cover, the strength of the polar vortex and the stratospheric ozone depletion are the primary factors that influence the surface UV radiation levels in Marambio. The lower UV irradiance values in 2017/2018 are explained by the high ozone concentrations in November, February and for a large part of October. The role of cloud cover was clearly seen in December, and to a lesser extent in October and November, when cloud cover qualitatively explains changes which could not be ascribed to changes in total ozone column (TOC). In this study, the roles of aerosols and albedo are of minor influence because the variation of these factors in Marambio was small from one year to the other. The largest variations of UV irradiance occur during spring and early summer when noon solar zenith angle (SZA) is low and the stratospheric ozone concentration is at a minimum (the so-called ozone hole). In 2017/2018, coincident low total ozone column and low cloudiness near solar noon did not occur, and no extreme UV indices were measured.

Connections Between Stratospheric Ozone Concentrations Over the Arctic and Sea Surface Temperatures in the North Pacific

AbstractWe examined the relationship between sea surface temperatures (SSTs) in the North Pacific and the concentration of stratospheric ozone in the northern hemisphere in February–March from 1980 to 2017 using reanalysis and satellite datasets. Our results show that the concentration of stratospheric ozone can be modulated by the principle mode of the North Pacific SSTs—that is, there are negative and zonally asymmetrical ozone anomalies in the Arctic stratosphere, but positive ozone anomalies in the lower stratosphere at mid‐latitudes during the positive phases of the North Pacific SSTs. The North Pacific SST anomalies account for about 20% of the linear variance of ozone concentrations in the lower stratosphere over the Arctic. Negative SST anomalies in the central North Pacific tend to result in a strengthened Western‐Pacific like teleconnection, which favors the propagation of more planetary wavenumber‐1 and ‐2 waves into the stratosphere. The North Pacific SSTs‐related upwelling branch of the Brewer–Dobson circulation in the mid‐latitude stratosphere strengthens, but its downwelling branch in the Arctic stratosphere weakens. This results in decreased ozone anomalies in the lower stratosphere over the Arctic and increased ozone anomalies in the lower stratosphere at mid‐latitudes. The zonally asymmetrical distribution of ozone related to the positive phase of SSTs over the North Pacific may be related to the shifting and strengthening of the stratospheric Arctic vortex.

On the Importance of Interactive Ozone Chemistry in Earth‐System Models for Studying Mesophere‐Lower Thermosphere Tidal Changes during Sudden Stratospheric Warmings

AbstractWe use the CESM2‐Whole Atmosphere Community Climate Model, to study the importance of ozone in the vertical coupling between lower and upper atmosphere during sudden stratospheric warmings (SSWs). During SSWs, the build up of stratospheric ozone concentrations at tropical latitudes and its increased asymmetrical distribution carries the potential to affect the generation of migrating and nonmigrating semidiurnal solar tides. Much of the upper atmospheric variability associated with SSWs is known to be driven by large changes in the vertically propagating semidiurnal migrating (SW2) and nonmigrating (SW1 and SW3) solar tides. In this study, we investigate the effect of stratospheric ozone variability during SSWs on these solar tides. For this purpose, a case study of the 2009 SSW event is carried out using the WACCM with two distinct simulation setups. In the first setup, the ozone concentrations are interactively calculated in the model and resemble the ozone observations during the 2009 SSW event, while in the second setup, the ozone concentrations are specified using zonal mean values. We constrain both of the simulations to the Modern‐Era Retrospective Analysis for Research and Applications‐2 reanalysis so that the background atmosphere through which the solar tides propagate are almost identical in each case. Following the onset of the SSW, we find that in the vicinity of the peak enhancements of SW1, SW2, and SW3 in the mesosphere‐lower thermosphere (MLT), the amplitudes of these semidiurnal solar tides are approximately about 15–50% larger for the simulation with interactive ozone as compared with the one with prescribed ozone, indicating that the stratospheric ozone variability plays an important role in driving semidiurnal solar tidal changes during SSWs.

Low yield and abiotic origin of N2O formed by the complete nitrifier Nitrospira inopinata

Nitrous oxide (N2O) and nitric oxide (NO) are atmospheric trace gases that contribute to climate change and affect stratospheric and ground-level ozone concentrations. Ammonia oxidizing bacteria (AOB) and archaea (AOA) are key players in the nitrogen cycle and major producers of N2O and NO globally. However, nothing is known about N2O and NO production by the recently discovered and widely distributed complete ammonia oxidizers (comammox). Here, we show that the comammox bacterium Nitrospira inopinata is sensitive to inhibition by an NO scavenger, cannot denitrify to N2O, and emits N2O at levels that are comparable to AOA but much lower than AOB. Furthermore, we demonstrate that N2O formed by N. inopinata formed under varying oxygen regimes originates from abiotic conversion of hydroxylamine. Our findings indicate that comammox microbes may produce less N2O during nitrification than AOB.

Recent Tropical Expansion: Natural Variability or Forced Response?

AbstractPrevious studies have documented a poleward shift in the subsiding branches of Earth’s Hadley circulation since 1979 but have disagreed on the causes of these observed changes and the ability of global climate models to capture them. This synthesis paper reexamines a number of contradictory claims in the past literature and finds that the tropical expansion indicated by modern reanalyses is within the bounds of models’ historical simulations for the period 1979–2005. Earlier conclusions that models were underestimating the observed trends relied on defining the Hadley circulation using the mass streamfunction from older reanalyses. The recent observed tropical expansion has similar magnitudes in the annual mean in the Northern Hemisphere (NH) and Southern Hemisphere (SH), but models suggest that the factors driving the expansion differ between the hemispheres. In the SH, increasing greenhouse gases (GHGs) and stratospheric ozone depletion contributed to tropical expansion over the late twentieth century, and if GHGs continue increasing, the SH tropical edge is projected to shift further poleward over the twenty-first century, even as stratospheric ozone concentrations recover. In the NH, the contribution of GHGs to tropical expansion is much smaller and will remain difficult to detect in a background of large natural variability, even by the end of the twenty-first century. To explain similar recent tropical expansion rates in the two hemispheres, natural variability must be taken into account. Recent coupled atmosphere–ocean variability, including the Pacific decadal oscillation, has contributed to tropical expansion. However, in models forced with observed sea surface temperatures, tropical expansion rates still vary widely because of internal atmospheric variability.

Quantifying the effects of a low-ozone event and shallow stratocumulus clouds on ultraviolet erythemal radiation exposure.

Meteorological and dosimetric ultraviolet (UV) erythemal radiation (UVER) measurements were performed in Didcot, England, on 6 and 7 April 2017. Both days were characterized by clear-sky conditions in the morning and the afternoon with development of shallow stratocumulus clouds (SSC) around noon. In addition, a low-ozone event occurred on 7 April characterized by a 34 DU (Dobson Unit) drop in total stratospheric ozone content. Compared to 6 April, the ozone mini-hole caused UVER increases of 2.67 standard erythema dose (SED) for diffuse and 4.32 SED for global radiation characterized by radiation amplification factors (RAF) of 1.62 and 1.52, respectively. The total global UVER dose reductions due to SSC coverage amount to 2.33 SED (6 April) and 2.81 SED (7 April). As innovation the RAF is decomposed into two parts, named cloud ozone factor (COF) and radiation amplification factor based on measured data (RAFm), to quantify the low-ozone event's effect and the SSC influence in independently modifying the UVER doses. Hereby, the weight of each of these two effects acting during the same low-ozone event is expressed by the new COF. In this case, the COF values range between -0.13 and -0.11 for diffuse UVER and -0.03 to -0.07 for the global UV and UV-B parts. A positive COF value (0.18) results for the global UV-A range.

Seasonal Evolution of Stratosphere‐Troposphere Coupling in the Southern Hemisphere and Implications for the Predictability of Surface Climate

AbstractStratosphere‐troposphere coupling in the Southern Hemisphere (SH) polar vortex is an important dynamical process that provides predictability of the tropospheric Southern Annular Mode (SAM) and its associated surface impacts. SH stratosphere‐troposphere coupling is explored by height‐time domain empirical orthogonal function (EOF) analysis applied to the zonal mean‐zonal wind anomalies averaged over the Antarctic circumpolar region (55–65°S; U55–65°S). The leading EOF explains 42% of the height‐time variance of U55–65°S and depicts the variations of the vortex that is tightly tied to the seasonal breakdown of the vortex during late spring. The leading EOF pattern, defined here as the stratosphere‐troposphere coupled mode, is characterized by variations in U55–65°S that develop in early winter near the stratopause, change sign from late winter to early spring, gain maximum amplitude during October in the upper stratosphere, and then extend downward to the surface from October to January. This stratosphere‐troposphere coupling during the spring months appears to be preconditioned by anomalies in upward propagating planetary wave activity and a meridional shift of the vortex as high as the stratopause and as early as June. Interannual variations of the stratosphere‐troposphere coupled mode are highly correlated with those of the tropospheric SAM, Antarctic stratospheric ozone concentration, Antarctic sea ice concentrations in the South Pacific and the Weddell Sea, and SH regional climate during late spring–early summer. Anomalies in the upper stratospheric flow as early as June are thus a potentially important source of predictability for the tropospheric SAM and its associated impacts on surface climate in spring and summer.

PC proxy: a method for dynamical tracer reconstruction

A detailed development of the principal component proxy method of dynamical tracer reconstruction is presented, including error analysis. The method works by correlating the largest principal components of a matrix representation of the transport dynamics with a set of sparse measurements. The Lyapunov spectrum was measured and used to quantify the lifetime of each principal component. The method was tested on the 500 K isentropic surface with stratospheric ozone concentration measurements from the Polar Aerosol and Ozone Measurement (POAM) III satellite instrument during October and November 1998 and compared with the older proxy tracer method which works by correlating measurements with a single other tracer or proxy. Using a 60 day integration time and five (5) principal components, cross validation of globally reconstructed ozone and comparison with ozone sondes returned root-mean-square errors of 0.16 ppmv and 0.36 ppmv, respectively. This compares favourably with the classic proxy tracer method in which a passive tracer equivalent latitude field was used for the proxy and which returned RMS errors of 0.22 ppmv and 0.59 ppmv for cross-validation and sonde validation respectively. The method seems especially effective for shorter lived tracers and was far more accurate than the classic method at predicting ozone concentration in the Southern hemisphere over the same time period. It is also more effective when reconstruction is performed over the entire Earth rather than a single hemisphere allowing for seamless reconstruction of global fields.

Concentration of Stratospheric Ozone Derived from Lidar, Satellite, and Surface Observations

Data of stratospheric ozone measurements with the AK-3 lidar over Obninsk in 2012–2015 are compared with Aura/MLS and Aura/OMI satellite data and parallel surface observations of total ozone (TO) with the Brewer spectrophotometer. The maximum difference in mean ozone concentration between the lidar and Aura/MLS data in the altitude range of 13 to 32 km does not exceed 0.2 x 1012 mol./cm3 (or the maximum of 9% at the altitude of 13 km). At the same time, Aura/OMI data have a positive bias of about 20% relative to lidar data in the range of 13 to 20 km that is associated with OMI measurement errors according to literature data. Total ozone values calculated from lidar measurements jointly with the known climatology data are compared with those measured with the Brewer spectrophotometer. It is demonstrated that the correlation between the results of measurements obtained by two methods is close to linear, and the mean relative difference in the overall measurement range does not exceed 5%.

Stratospheric ozone loss over the Eurasian continent induced by the polar vortex shift

The Montreal Protocol has succeeded in limiting major ozone-depleting substance emissions, and consequently stratospheric ozone concentrations are expected to recover this century. However, there is a large uncertainty in the rate of regional ozone recovery in the Northern Hemisphere. Here we identify a Eurasia-North America dipole mode in the total column ozone over the Northern Hemisphere, showing negative and positive total column ozone anomaly centres over Eurasia and North America, respectively. The positive trend of this mode explains an enhanced total column ozone decline over the Eurasian continent in the past three decades, which is closely related to the polar vortex shift towards Eurasia. Multiple chemistry-climate-model simulations indicate that the positive Eurasia-North America dipole trend in late winter is likely to continue in the near future. Our findings suggest that the anticipated ozone recovery in late winter will be sensitive not only to the ozone-depleting substance decline but also to the polar vortex changes, and could be substantially delayed in some regions of the Northern Hemisphere extratropics.

Study nonlinear dynamics of stratospheric ozone concentration at Pakistan Terrestrial region

This study investigates the nonlinear dynamics of the stratospheric ozone layer at Pakistan atmospheric region. Ozone considered now the most important issue in the world because of its diverse effects on earth biosphere, including human health, ecosystem, marine life, agriculture yield and climate change. Therefore, this paper deals with total monthly time series data of stratospheric ozone over the Pakistan atmospheric region from 1970 to 2013. Two approaches, basic statistical analysis and Fractal dimension (D) have adapted to study the nature of nonlinear dynamics of stratospheric ozone level. Results obtained from this research have shown that the Hurst exponent values of both methods of fractal dimension revealed an anti-persistent behavior (negatively correlated), i.e. decreasing trend for all lags and Rescaled range analysis is more appropriate as compared to Detrended fluctuation analysis. For seasonal time series all month follows an anti-persistent behavior except in the month of November which shown persistence behavior i.e. time series is an independent and increasing trend. The normality test statistics also confirmed the nonlinear behavior of ozone and the rejection of hypothesis indicates the strong evidence of the complexity of data. This study will be useful to the researchers working in the same field in the future to verify the complex nature of stratospheric ozone.

Ultraviolet-B alleviates the uncoupling effect of elevated CO2and increased temperature on grape berry (Vitis viniferacv. Tempranillo) anthocyanin and sugar accumulation

Background and Aims Atmospheric carbon dioxide (CO2) levels and temperature are expected to increase in the next decades. In addition, changes in climate as well as the stratospheric ozone concentration may affect the exposure of viticultural regions to UV-B. The aim of the present study was to investigate the effect of combined elevated CO2 and increased temperature (+CO2/+T) regimes and UV-B radiation on anthocyanin and flavonol biosynthesis in grape berries. Methods and Results Three UV-B doses [0, 5.98 and 9.66 kJ/(m2·d)] and two CO2–day/night temperature regimes (390 μmol/mol CO2–24/14°C and 700 μmol/mol CO2–28/18°C) were imposed on Vitis vinifera cv. Tempranillo fruit-bearing cuttings from fruitset to maturity. Berry mass, composition and expression of selected genes were monitored. The time to reach veraison and maturity was reduced under +CO2/+T. Anthocyanin concentration under +CO2/+T was higher 2 weeks after veraison, but lower at maturity. Ultraviolet-B radiation slowed berry development and upregulated flavonol and anthocyanin biosynthesis. Conclusions The effect of UV-B, which modulates the accumulation of sugars and upregulates anthocyanin biosynthesis, compensated the deleterious effect of elevated CO2 and increased temperature on berry anthocyanin concentration. Significance of the Study Certain viticultural practices, such as leaf removal, that modify the exposure of grapes to UV-B and the leaf surface to fruit mass ratio, may alleviate the effect of elevated CO2 and increased temperature on grape anthocyanin concentration.

Size dependence of ozone lamina characteristics and their correlations

Ozone profiles contain narrow layers of substantially enhanced or reduced ozone, called positive and negative laminae, respectively. They reflect both evolutions of stratospheric ozone content and stratospheric dynamics. Here we deal only with positive laminae. The following lamina characteristics are investigated in dependence on lamina size: the number of laminae per profile, the overall ozone amount in laminae per profile and the ozone amount in one lamina at the European ozonosonde stations. An important role of the vertical resolution of ozonesonde measurements is specified. Lamina characteristics for Legionowo and Lindenberg, and small lamina (<2mPa) characteristics for all stations suffer with effects of vertical resolution of measurements. For this reason they are not used here for long-term trend investigations. The long-term evolution of the ozone amount in one lamina does not display a trend. The results for the three remaining stations, Hohenpeissenberg, Payerne and Uccle, are largely consistent with our previous results on lamina behaviour, which means that our previous results on trends in laminae (e.g., Križan and Laštovička, 2005; Laštovička et al., 2014) are basically correct. The number of laminae per profile and the overall ozone amount in laminae per profile show negative trends before (1979–1995) and rather positive trends after (1996–2011) the reversal of trends in total columnar ozone over Europe. Both parameters reach the highest values for small laminae and with increasing size they decrease. Correlations between characteristics of laminae of different size ranges at individual stations are better for neighbour lamina ranges than for distant lamina ranges. The number of statistically significant correlations of laminae of the same size between pairs of stations is much higher for large laminae above 4mPa, probably due to processes responsible for their formation and their expected larger horizontal size.

A comparison of stratospheric photochemical response to different reconstructions of solar ultraviolet radiative variability

We present calculations of stratospheric chemical abundances variations between different levels of solar activity using a simple photochemistry model in transient chemistry mode. Different models for the reconstruction of the solar spectrum, as well as observations from the SOLar STellar Irradiance Comparison Experiment (SOLSTICE) and Spectral Irradiance Monitor (SIM) on the SOlar Radiation and Climate Experiment (SORCE) satellite, are used as inputs to the calculations. We put the emphasis on the MOnte CArlo Spectral Solar Irradiance Model (MOCASSIM) reconstructions, which cover the spectral interval from 150 to 400nm and extend from 1610 to present. We compare our results with those obtained with the Naval Research Laboratory Solar Spectral Irradiance (NRLSSI) model as well as with the Magnesium-Neutron Monitor (MGNM) model over a period of time spanning the ascending phase of Cycle 22. We also perform the calculations using SORCE composite spectra for the descending phase of Cycle 23 and with the reconstructed MOCASSIM, NRLSSI and MGNM spectra for the same period for comparison. Finally, we compare the chemical abundances obtained for the Maunder Minimum with those obtained for the Cycle 23 minimum (in March 2009) and find that stratospheric ozone concentration was slightly higher during the recent minimum, consequent to the small positive variability between the MOCASSIM spectra for both epochs, especially below 260nm. We find that the response in stratospheric ozone is not only dependent on the variability amplitude in the solar spectrum (especially in the 200–240nm band), but also significantly on the base level of the minimum solar spectrum.

The Transient Circulation Response to Radiative Forcings and Sea Surface Warming*

Abstract Tropospheric circulation shifts have strong potential to impact surface climate. However, the magnitude of these shifts in a changing climate and the attending regional hydrological changes are difficult to project. Part of this difficulty arises from the lack of understanding of the physical mechanisms behind the circulation shifts themselves. To better delineate circulation shifts and their respective causes the circulation response is decomposed into 1) the “direct” response to radiative forcings themselves and 2) the “indirect” response to changing sea surface temperatures. Using ensembles of 90-day climate model simulations with immediate switch-on forcings, including perturbed greenhouse gas concentrations, stratospheric ozone concentrations, and sea surface temperatures, this paper documents the direct and indirect transient responses of the zonal-mean general circulation, and investigates the roles of previously proposed mechanisms in shifting the midlatitude jet. It is found that both the direct and indirect wind responses often begin in the lower stratosphere. Changes in midlatitude eddies are ubiquitous and synchronous with the midlatitude zonal wind response. Shifts in the critical latitude of wave absorption on either flank of the jet are not indicted as primary factors for the poleward-shifting jet, although some evidence for increasing equatorward wave reflection over the Southern Hemisphere in response to sea surface warming is seen. Mechanisms for the Northern Hemisphere jet shift are less clear.

Effect of tropospheric and stratospheric temperatures on tropopause height

Troposphere is an important layer of the atmosphere because most of the weather phenomena are confined to this layer. Variations in tropopause height significantly depend upon the changes in upper tropospheric and lower stratospheric temperature. Availability of global positioning system radio occultation high vertical temperature profiles on better temporal and spatial scales gives an opportunity to study the tropopause height variations with respect to tropospheric and stratospheric temperatures. Analysing these profiles along with in situ observations, we studied the impact of stratospheric and tropospheric warming or cooling on tropopause height over Indian region. Decrease in stratospheric temperature increases the tropopause height, and increase in tropospheric temperature decreases the tropopause height. Stratospheric temperature is found to have more impact on tropopause height compared to tropospheric temperature, and this impact is more evident over ocean than land. The analysis also brings out a good correlation between stratospheric ozone concentrations and its temperature. In the light of decreasing stratospheric ozone concentrations due to global warming, this study points out towards a possibility of increase in tropopause height.

Skillful Seasonal Prediction of the Southern Annular Mode and Antarctic Ozone

Abstract Using a set of seasonal hindcast simulations produced by the Met Office Global Seasonal Forecast System, version 5 (GloSea5), significant predictability of the southern annular mode (SAM) is demonstrated during the austral spring. The correlation of the September–November mean SAM with observed values is 0.64, which is statistically significant at the 95% confidence level [confidence interval: (0.18, 0.92)], and is similar to that found recently for the North Atlantic Oscillation in the same system. Significant skill is also found in the prediction of the strength of the Antarctic stratospheric polar vortex at 1 month average lead times. Because of the observed strong correlation between interannual variability in the strength of the Antarctic stratospheric circulation and ozone concentrations, it is possible to make skillful predictions of Antarctic column ozone amounts. By studying the variation of forecast skill with time and height, it is shown that skillful predictions of the SAM are significantly influenced by stratospheric anomalies that descend with time and are coupled with the troposphere. This effect allows skillful statistical forecasts of the October mean SAM to be produced based only on midstratosphere anomalies on 1 August. Together, these results both demonstrate a significant advance in the skill of seasonal forecasts of the Southern Hemisphere and highlight the importance of accurate modeling and observation of the stratosphere in producing long-range forecasts.

Diffuse Attenuation Coefficients for East Antarctic Pack Ice and Snow at Ultraviolet and Visible Wavelengths

Declining stratospheric ozone concentrations have led to higher levels of ultraviolet (UV) B (UVB) radiation at the Earth's surface, particularly in Antarctic spring time. Increased exposure to UVB radiation can decrease the productivity of sea-ice algae, as well as cause damage to organisms living in the clear water beneath the Antarctic pack ice. Conversely, sea-ice algae and other photosynthetic organisms rely on photosynthetically active radiation (PAR) to drive and sustain growth. Field work performed during the 2007 Australian Antarctic Program Sea Ice Physics and Ecosystem eXperiment voyage to the East Antarctic sea-ice zone allowed the estimation of diffuse attenuation coefficients for pack ice and the overlying snow at UV wavelengths (305, 313, 320, 340, 380, and 395 nm) and for PAR. The UV attenuation coefficients were 9.6-12.7 m-1 for snow and 1.57-2.05 m-1 for pack ice. The PAR attenuation coefficients were 10.5 m-1 (snow) and 1.52 m-1 (pack ice). The attenuation coefficients for erythemally weighted UVB radiation were 11.3 m-1 (snow) and 1.82 m-1 (pack ice). The analysis also estimated the reflection coefficient (albedo) of snow as 0.67 for UV wavelengths and 0.68 for PAR, but the snow cover was not always optically thick.

Impact of geomagnetic excursions on atmospheric chemistry and dynamics

Abstract. Geomagnetic excursions, i.e. short periods in time with much weaker geomagnetic fields and substantial changes in the position of the geomagnetic pole, occurred repeatedly in the Earth's history, e.g. the Laschamp event about 41 kyr ago. Although the next such excursion is certain to come, little is known about the timing and possible consequences for the state of the atmosphere and the ecosystems. Here we use the global chemistry climate model SOCOL-MPIOM to simulate the effects of geomagnetic excursions on atmospheric ionization, chemistry and dynamics. Our simulations show significantly increased concentrations of nitrogen oxides (NOx) in the entire stratosphere, especially over Antarctica (+15%), due to enhanced ionization by galactic cosmic rays. Hydrogen oxides (HOx) are also produced in greater amounts (up to +40%) in the tropical and subtropical lower stratosphere, while their destruction by reactions with enhanced NOx prevails over the poles and in high altitudes (by −5%). Stratospheric ozone concentrations decrease globally above 20 km by 1–2% and at the northern hemispheric tropopause by up to 5% owing to the accelerated NOx-induced destruction. A 5% increase is found in the southern lower stratosphere and troposphere. In response to these changes in ozone and the concomitant changes in atmospheric heating rates, the Arctic vortex intensifies in boreal winter, while the Antarctic vortex weakens in austral winter and spring. Surface wind anomalies show significant intensification of the southern westerlies at their poleward edge during austral winter and a pronounced northward shift in spring. Major impacts on the global climate seem unlikely.

Contrasting Sensitivity of Marine Biota to UV-B Radiation Between Southern and Northern Hemispheres

The asymmetries between hemispheres in stratospheric ozone concentration and atmospheric aerosols, leading to differences in incident ultraviolet B (UV-B) radiation, were examined in order to resolve the differential forcing of adaptation and selection of marine organisms under elevated UV-B radiation. This analysis was based on a meta-analysis including 2,060 experimental assessments of responses of marine organisms from the Northern and Southern Hemispheres to UV-B. Stratospheric ozone concentration in spring and summer decreased by 11.0 % in the Southern and 2.7 % in the Northern between 1970 and 2012, indicating higher UV-B incidence on the Southern Hemisphere. The ratio of studies on UV-B radiation impacts performed in the Southern against the Northern Hemisphere was 0.34 indicating higher research effort in the Northern Hemisphere. Responses of marine biota to UV-B indicated significantly more resistance of marine organisms tested from the Southern Hemisphere (P < 0.01) to UV-B radiation. Marine plants (angiosperm, macroalgae and microalgae) showed no significant differences in UV-B sensitivity between hemispheres, but the family Ulvaceae, showed significantly more resistance to UV-B for organisms tested from the Southern Hemisphere (P < 0.005). Echinodermata tested from the Southern Hemisphere were more resistant to UV-B (P < 0.005), as well as early stages of marine organisms (P < 0.001). Responses at the molecular and cellular level and demographic levels showed lower UV-B effects in the organisms tested from the Southern Hemisphere. The results obtained suggest that marine organisms from the Southern Hemisphere tend to be more resistant to UV-B radiation than those in the Northern Hemisphere.