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This study investigates the influence of the 2015 Calbuco eruption (41.2∘ S, 72.4∘ W; Chile) on the total columnar aerosol optical properties over the Southern Hemisphere. The well-known technic of sun photometry was applied for the investigation of the transport and spatio-temporal evolution of the optical properties of the volcanic plume. The CIMEL sun photometer measurements performed at six South American and three African sites were statistically analysed. This study involves the use of the satellite observations and a back-trajectory model. The passage of the Calbuco plume is statistically detectable in the aerosol optical depth (AOD) observations obtained from sun photometer and MODIS observations. This statistical detection confirms that the majority of the plume was transported over the northeastern parts of South America and reached the South African region 1 week after the eruption. The plume impacted the southern parts of South America to a lesser extent. The highest AOD anomalies were observed over the northeastern parts of South America. Over the South African sites, the AOD anomalies induced by the spread of the plume were quite homogeneously distributed between the east and west coasts. The optical characteristics of the plume near the source region were consistent with an ash-bearing plume. Conversely, sites further from the Calbuco volcano were influenced by ash-free plume. The optical properties discussed in this paper will be used as inputs for numerical models for further investigation of the ageing of the Calbuco plume in a forthcoming study. Fil: Bègue, Nelson. Université de la Réunion; Francia. Centre National de la Recherche Scientifique; Francia Fil: Shikwambana, Lerato. University of Kwazulu Natal; Sudáfrica. South African National Space Agency; Sudáfrica Fil: Bencherif, Hassan. Université de la Réunion; Francia. University of Kwazulu Natal; Sudáfrica Fil: Pallotta, Juan Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina Fil: Sivakumar, Venkataraman. University of Kwazulu Natal; Sudáfrica Fil: Wolfram, Elian Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina Fil: Mbatha, Nkanyiso. University Of Zululand; Sudáfrica Fil: Orte, Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina Fil: Jean Du Preez, David. Université de la Réunion; Francia. University of Pretoria; Sudáfrica Fil: Ranaivombola, Marion. Université de la Réunion; Francia Fil: Piketh, Stuart. North-west University; Sudáfrica Fil: Formenti, Paola. Universite de Paris; Francia

This work presents a practical approach to obtain the dispersion curves for a plate via numerical modelling using the commercial software ANSYS. The method is based on the dynamic analysis of the waveguide to extract the mode shapes (eigenvectors) for each resonant frequency (eigenvalue) from the natural frequency response without damping. Each eigenvalue provides a frequency and the dimensions of the model (wavelength), which are the basis of the dispersion curves. Then, an algorithm is developed in MATLAB to stack the different mode solutions with its respective frequencies using the modal assurance criterion. The data obtained is compared with the dispersion curves provided by the GUIGW software.

Subpolar regions in the Southern Hemisphere are influenced by the Antarctic polar vortex during austral spring, which induces high and short-term ozone variability at different altitudes, mainly into the stratosphere. This variation may affect considerably the total ozone column changing the harmful UV radiation that reaches the surface. With the aim of studying ozone with a high time resolution at different altitudes in subpolar regions, a millimetre-wave radiometer (MWR) was installed at the Observatorio Atmosférico de la Patagonia Austral (OAPA), Río Gallegos, Argentina (51.6∘ S, 69.3∘ W), in 2011. This instrument provides ozone profiles with a time resolution of ∼1 h, which enables studies of short-term ozone mixing ratio variability from 25 to ∼70 km in altitude. This work presents the MWR ozone observations between October 2014 and 2015, focusing on an atypical event of the polar vortex and Antarctic ozone hole influence over Río Gallegos detected from the MWR measurements at 27 and 37 km during November of 2014. During the event, the MWR observations at both altitudes show a decrease in ozone followed by a local peak of ozone amount of the order of hours. This local recovery is observed thanks to the high time resolution of the MWR mentioned. The advected potential vorticity (APV) calculated from the MIMOSA high-resolution advection model (Modélisation Isentrope du transport Méso-échelle de l'Ozone Stratosphérique par Advection) was also analysed at two isentropic levels (levels of constant potential temperature) of 675 and 950 K (∼27 and ∼37 km of altitude, respectively) to understand and explain the dynamics at both altitudes and correlate the ozone rapid recovery with the passage of a tongue with low PV values over Río Gallegos. In addition, the MWR dataset was compared for the first time with measurements obtained from the Microwave Limb Sounder (MLS) at individual altitude levels (27, 37 and 65 km) and with the differential absorption lidar (DIAL) installed in the OAPA to analyse the correspondence between the MWR and independent instruments. The MWR–MLS comparison presents a reasonable correlation with mean bias errors of +5 %, −11 % and −7 % at 27, 37 and 65 km, respectively. The MWR–DIAL comparison at 27 km also presents good agreement, with a mean bias error of −1 %. Fil: Orte, Pablo Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Centre National de la Recherche Scientifique; Francia Fil: Wolfram, Elian Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina Fil: Salvador, Jacobo Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina Fil: Mizuno, Akira. Nagoya University; Japón Fil: Bègue, Nelson. Université de La Réunion; Francia. Centre National de la Recherche Scientifique; Francia Fil: Bencherif, Hassan. Université de La Réunion; Francia. Centre National de la Recherche Scientifique; Francia. University of KwaZulu Natal; Sudáfrica Fil: Bali, Juan Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina Fil: D'Elia, Raul. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina Fil: Pazmiño, Andrea. Université Pierre et Marie Curie; Francia. Université Versailles St Quentin en Yvelines; Francia. Centre National de la Recherche Scientifique; Francia Fil: Godin Beekmann, Sophie. Université Pierre et Marie Curie; Francia. Université Versailles St Quentin en Yvelines; Francia. Centre National de la Recherche Scientifique; Francia Fil: Ohyama, Hirofumi. National Institute for Environmental Studies; Japón Fil: Quiroga, Jonathan Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina

Gravity wave (GW) activity is analyzed using temperature (T) data retrieved from a Rayleigh light detection and ranging (lidar) at Río Gallegos, Argentina (51.6°S, 69.3°W). GW characteristics are derived from 302 nights of observations providing more than 1,018 hr of high-resolution lidar data between 20- and 56-km height from August 2005 to December 2015. T measurements are performed by a Differential Absorption Lidar instrument. This lidar was the southernmost outside Antarctica until the end of 2017. Río Gallegos is an exceptional place to observe large amplitude GW. Every lidar measurement is classified according to its relative position to the polar vortex. The lidar measurements are compared with collocated Sounding of the Atmosphere using Broadband Emission Radiometry and Global Positioning System-Radio Occultation data. The different instruments show different windows of the GW spectrum, providing complementary observations. In general, the geometric mean of the specific GW potential energy (PE) is larger during winter and spring than during summer and autumn. The largest geometric mean of PE is found inside the vortex and decreases monotonically at its edge, outside it and when there is no vortex. The same behavior is observed with satellite data. On average, it can be seen that lidar observations provide larger PE values than limb sounding measurements. From a Morlet continuous wavelet transform analysis, three distinct modes are captured from Sounding of the Atmosphere using Broadband Emission Radiometry and from Global Positioning System-Radio Occultation data at the upper and lower stratosphere, respectively. In particular, a systematic 3.5- to 4-year oscillation, possibly related to El Niño–Southern Oscillation is observed. Fil: Llamedo Soria, Pablo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería. Laboratorio de Investigación Desarrollo y Transferencia - Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Laboratorio de Investigación Desarrollo y Transferencia; Argentina Fil: Salvador, Jacobo Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Universidad Nacional de la Patagonia Austral. Unidad Académica Río Gallegos; Argentina Fil: de la Torre, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería. Laboratorio de Investigación Desarrollo y Transferencia - Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Laboratorio de Investigación Desarrollo y Transferencia; Argentina Fil: Quiroga, Jonathan Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Universidad Nacional de la Patagonia Austral. Unidad Académica Río Gallegos; Argentina Fil: Alexander, Pedro Manfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina Fil: Hierro, Rodrigo Federico. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería. Laboratorio de Investigación Desarrollo y Transferencia - Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Laboratorio de Investigación Desarrollo y Transferencia; Argentina Fil: Schmidt, T.. Helmholtz Centre Potsdam; Alemania Fil: Pazmiño, A.. Université Pierre et Marie Curie; Francia. Centre National de la Recherche Scientifique; Francia. Universite de Paris VI; Francia Fil: Quel, Eduardo Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina

International audience; In recent years, many analyses of space- and ground-based data records reported signs or evidence of increasing ozone concentrations in the extrapolar upper stratosphere since the late 1990s. However, the magnitude and significance of the trend estimates vary from one study to another, prompting the ozone research community to further investigate the causes of these differences. A broader consensus has emerged in the past year, placing the positive trend in the upper stratosphere on solid ground and heralding the start of an observation-based exploration of the recovery of stratospheric ozone. More accurate trend estimates are needed to identify the geophysical processes contributing to the recovery and their relative importance. Uncovering seasonal and spatial trend patterns will be key in reaching this objective, not just in the extrapolar upper stratosphere but elsewhere as well.However, at the moment, it remains unclear whether current ozone profile observing systems are able to provide this information. We address this question with an exploration of the capabilities and limitations of current data records in space (limb/occultation sounders) and on the ground (NDACC/GAW/SHADOZ-affiliated sonde, stratospheric lidar and microwave radiometer sites) to infer decadal trends and their vertical, latitudinal and seasonal patterns. We focus on long-term stability, one of the key drivers of the ability to detect trends. We present updated results of a comprehensive analysis that allowed us to quantify the drift of satellite data relative to the ground-based networks (Hubert et al., 2016). In a companion analysis we exploited the satellite data to uncover temporal and spatial inhomogeneities in the ground-based time series, some of which were traced to known changes occurring at different moments across the network. These changes add to the challenge to derive unbiased ozone trends from ground-based observations and they impede our ability to constrain satellite drift to the level required for current and future ozone trend assessments. We conclude that ongoing efforts to homogenise the ground-based data records are essential.

The long-term evolution of total ozone column inside the Antarctic polar vortex is investigated over the 1980-2016 period. Trend analyses are performed using a multilinear regression (MLR) model based on various proxies (heat flux, QBO, solar flux, AAO and aerosols). Annual total ozone column corresponding to the mean monthly values inside the vortex in September and during the period of maximum ozone depletion from September 15th to October 15th are used. Total ozone columns from combined TOMS-N7, SBUV-N9, TOMS-EP and OMI-TOMS satellite datasets and the Multi-Sensor Reanalysis (MRS-2) dataset are considered in the study. Ozone trends are computed by a piecewise trend model (PWT) before and after the turnaround in 2001. In order to evaluate total ozone within the vortex, two classification methods are used, based on the potential vorticity gradient as a function of equivalent latitude. The first standard one, considers this gradient at a single isentropic level (475K or 550K), while the second one uses a range of isentropic levels between 400K and 600K. The regression model includes a new proxy that represents the stability of the vortex during the studied month period. The determination coefficient (R2) between observations and modeled values increases by ~0.05 when this proxy is included in the MLR model. The higher R2 (0.93-0.95) and the minimum residuals are found for the second classification method in the case of both datasets and months periods. Trends in September are statistically significant at 2 sigma level with values ranging between 1.85 and 2.67 DU yr-1 depending on the methods and data sets. This result confirms the recent studies of Antarctic ozone healing during that month. Trends after 2001 are 2 to 3 times lower than before the turnaround year as expected from the response to the slowly ODS decrease in Polar regions.Estimated trends in the 15Sept-15Oct period are smaller than in September. They vary from 1.15 to 1.78 DU yr-1 and are hardly significant at 2 level. Ozone recovery is also confirmed by a steady decrease of the relative area of total ozone values lower than 150 DU within the vortex in the 15Sept-15Oct period since 2010. Comparison of the evolution of the ozone hole area in September and October show a decrease in September, confirming the later formation of the ozone hole during that month. Fil: Pazmino, Andrea. Universidad Paris Saclay; Francia Fil: Godin Beekmann, Sophie. Universidad Paris Saclay; Francia Fil: Hauchecorne, Alain. Universidad Paris Saclay; Francia Fil: Claud, Chantal. Ecole Polytechnique; Francia Fil: Khaykin, Sergey. Universidad Paris Saclay; Francia Fil: Goutail, Florence. Universidad Paris Saclay; Francia Fil: Wolfram, Elian Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Ministerio de Defensa; Argentina Fil: Salvador, Jacobo Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Ministerio de Defensa; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Universidad Nacional de la Patagonia Austral; Argentina Fil: Quel, Eduardo Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; Argentina. Ministerio de Defensa; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina

International audience; Taking into account the context of volcanic ash observation, an expert group has studied what is feasible to assess in order to give reliable Lidar information to aviation concerning ash detection. Lidar parameters to be evaluated and the associated methodology have been reported concerning the aerosol cloud detection, attribution and quantification.

The long-term evolution of total ozone column inside the Antarctic polar vortex is investigated over the 1980–2016 period. Trend analyses are performed using a multilinear regression (MLR) model based on various proxies (heat flux, Quasi-Biennial Oscillation, solar flux, Antarctic Oscillation and aerosols). Annual total ozone column corresponding to the mean monthly values inside the vortex in September and during the period of maximum ozone depletion from September 15th to October 15th are used. Total ozone columns from combined SBUV, TOMS and OMI satellite datasets and the Multi-Sensor Reanalysis (MSR-2) dataset are considered in the study. Ozone trends are computed by a piecewise trend model (PWT) before and after the turnaround in 2001. In order to evaluate total ozone within the vortex, two classification methods are used, based on the potential vorticity gradient as a function of equivalent latitude. The first standard one considers this gradient at a single isentropic level (475 K or 550 K), while the second one uses a range of isentropic levels between 400 K and 600 K. The regression model includes a new proxy that represents the stability of the vortex during the studied month period. The determination coefficient (R2) between observations and modeled values increases by ~ 0.05 when this proxy is included in the MLR model. The higher R2 (0.93–0.95) and the minimum residuals are observed for the second classification method for both datasets and months periods. Trends in September are statistically significant at 2 sigma level over 2001–2016 period with values ranging between 1.85 and 2.67 DU yr−1 depending on the methods and data sets. This result confirms the recent studies of Antarctic ozone healing during that month. Trends after 2001 are 2 to 3 times lower than before the turnaround year as expected from the response to the slowly ozone-depleting substances decrease in Polar regions. Estimated trends in the 15 Sept–15 Oct period are smaller than in September. They vary from 1.15 to 1.78 DU yr−1 and are hardly significant at 2σ level. Ozone recovery is also confirmed by a steady decrease of the relative area of total ozone values lower than 150 DU within the vortex in the 15 Sept–15 Oct period since 2010. Comparison of the evolution of the ozone hole area in September and October shows a decrease in September, confirming the later formation of the ozone hole during that month.

Composite materials are joined in many occasions with adhesive joints due to the condition of the materials, the ease of repair, the loading conditions, the affectation by corrosion and chemical attacks. However, the efficiency of these bonding schemes is related to multiple factors, among them, the length and the width of the adhesion zone and the thickness of the adhesive. In this work, we analyze the factors associated with the surface contact of the substrates. We define a numerical model using the finite element method and study the parameters related to the physical condition, considering optimal results based on the data of the strength provided by the suppliers of adhesives.

International audience; The latest assessment report on the state of the ozone layer (WMO 2014) confirmed the stabilization of the ozone loss in Antarctica since 2000. Several studies have been made in order to quantify the increase in total ozone column (TOC) in the Antarctic polar vortex in spring directly linked to the small decrease of ozone depleting substances levels in the polar stratosphere. These studies generally show a significant increase of TOC averaged inside the vortex since 2000 but they differ on the proxies used for the quantification of ozone interannual variability.In this study, the trend of TOC inside the vortex is analyzed over the 1980-2015 period using multilinear regression model based on various proxies (heat flux, QBO, solar flux, AAO and aerosols). The ozone trend is simulated by a piecewise linear trend (PWLT) before and after the break year in 2000, corresponding to the change of slope in ozone long-term evolution. The originality of this study is to take into account the baroclinicity of the vortex. For this, two different methods are used to classify TOC values inside the vortex as a function of Equivalent Latitude (EL). In the first standard one, the Nash criterion (Nash et al., 1996) is applied at a single isentropic level (475K or 550K). In the second one it is applied to a range of isentropic levels between 400K and 600K with a step of 25K.The study is focused on the period September 15 - October 15, the most representative of low ozone levels inside the vortex. The trend model is applied to SAOZ UV-Vis spectrometer data at Dumont d’Urville (66.7 ̊S, 140 ̊E) and also to TOMS/OMI above Antarctica and the trend results are presented for the different classification methods.

The ozone profile records of a large number of limb and occultation satellite instruments are widely used to address several key questions in ozone research. Further progress in some domains depends on a more detailed understanding of these data sets, especially of their long-term stability and their mutual consistency. To this end, we made a systematic assessment of 14 limb and occultation sounders that, together, provide more than three decades of global ozone profile measurements. In particular, we considered the latest operational Level-2 records by SAGE II, SAGE III, HALOE, UARS MLS, Aura MLS, POAM II, POAM III, OSIRIS, SMR, GOMOS, MIPAS, SCIAMACHY, ACE-FTS and MAESTRO. Central to our work is a consistent and robust analysis of the comparisons against the ground-based ozonesonde and stratospheric ozone lidar networks. It allowed us to investigate, from the troposphere up to the stratopause, the following main aspects of satellite data quality: long-term stability, overall bias and short-term variability, together with their dependence on geophysical parameters and profile representation. In addition, it permitted us to quantify the overall consistency between the ozone profilers. Generally, we found that between 20 and 40 km the satellite ozone measurement biases are smaller than ±5 %, the short-term variabilities are less than 5–12 % and the drifts are at most ±5 % decade−1 (or even ±3 % decade−1 for a few records). The agreement with ground-based data degrades somewhat towards the stratopause and especially towards the tropopause where natural variability and low ozone abundances impede a more precise analysis. In part of the stratosphere a few records deviate from the preceding general conclusions; we identified biases of 10 % and more (POAM II and SCIAMACHY), markedly higher single-profile variability (SMR and SCIAMACHY) and significant long-term drifts (SCIAMACHY, OSIRIS, HALOE and possibly GOMOS and SMR as well). Furthermore, we reflected on the repercussions of our findings for the construction, analysis and interpretation of merged data records. Most notably, the discrepancies between several recent ozone profile trend assessments can be mostly explained by instrumental drift. This clearly demonstrates the need for systematic comprehensive multi-instrument comparison analyses.

Reverdin, Gilles ... et. al.-- Special issue on SPURS: Salinity Processes in the Upper-ocean Regional Study.-- 10 pages, 7 figures, We investigated a 100 × 100 km high-salinity region of the North Atlantic subtropical gyre during the Sub-Tropical Atlantic Surface Salinity Experiment/Salinity Processes in the Upper-ocean Regional Study (STRASSE/SPURS) cruise from August 21, 2012, to September 9, 2012. Results showed great variability in sea surface salinity (SSS; over 0.3 psu) in the mesoscale, over 7 cm of total evaporation, and little diapycnal mixing below 36 m depth, the deepest mixed layers encountered. Strong currents in the southwestern part of the domain, and the penetration of freshwater, suggest that advection contributed greatly to salinity evolution. However, it was further observed that a smaller cyclonic structure tucked between the high SSS band and the strongest currents contributed to the transport of high SSS water along a narrow front. Cross-frontal transport by mixing is also a possible cause of summertime reduction of SSS. The observed structure was also responsible for significant southward salt transport over more than 200 km. © 2015 by The Oceanography Society. All rights reserved, This effort was supported nationally in France by CNES/TOSCA with the Gloscal and SMOS projects and by LEFE/INSU for the STRASSE/SPURS project, in Spain at ICM/CSIC by the Spanish national R+D plan (project AYA2010-22062-C05). The cruise took place on board R/V Thalassa owned by IFREMER and operated by GENAVIR. Support from the ship’s captain and crew during the STRASSE cruise is gratefully acknowledged. Some French instruments were also funded by INSU and IFREMER, and the trimaran platform Ocarina was also partially funded by IPSL. Nicolas Kolodziejczyk’s postdoctoral fellowship was awarded by CNES. Support for ASIP work is from the Office of Naval Research under Award No. N62909-12-1-7064, and Graig Sutherland’s scholarship PGSD3-410251-258 2011 was awarded by the National Research Council of Canada. SVP drifters were provided by the Global Drifter Program, NOAA grant #NA10OAR432056. LC and VH were supported by NASA grant #NNX12AI67G and NOAA grant #NA10OAR432056

International audience; Solar erythemal UV radiation incident on Argentina from tropical to high latitude regions has been measured with ground-based instruments as well as with the TOMS instrument on board of the NASA Earth-Probe satellite. These data permit validation of the UV index, a measure of solar risk to UV exposure, forecasted daily by CONAE (Argentina National Commission on Space Activities) and the Argentine National Weather Service. Model calculations of this index are also presented. In addition, we analyzed the UV effects from the Antarctic ozone hole passing over the continental part of the country using TOMS data corrected by a factor derived from the intercomparison of TOMS satellite data with those determined with Southern Hemisphere ground-based spectroradiometers. In this way, we obtained a rather comprehensive description of the amount of erythemal UV radiation and consequently of the UV index for the entire country, as well as the ozone total column and profile (the latter one at Buenos Aires). The results presented in this work were determined through collaboration between the following institutions: GSFC/NASA in USA, Institute Pierre Simon Laplace in France, University of Innsbruck in Austria and CEILAP, IFIR, CONAE, SMN, Universities of Rosario and San Luis in Argentina. The need to use erythemal irradiance and ozone results in Argentina, one of the most exposed regions of the Southern Hemisphere to study the effects of ozone depletion and consequently UV detrimental effects, has been partially covered in the framework of this North–South collaboration.

International audience; A ground-based DIfferential Absorption Lidar (DIAL) system has been implemented at CEILAP (CITEFA-CONICET) laboratory (34°33′S, 58°30′W), located in the Buenos Aires industrial suburbs. The goal is to perform measurements of the stratospheric ozone layer. Systematic measurements of ozone concentration profiles from ∼18 to ∼35 km altitude are performed since early 1999. Our measurements are carried out in 5 h in average during the night and in cloudless conditions. The DIAL system allows us to calculate directly the ozone profile from the lidar backscattering radiation since it is a self-calibrating technique. The signal processing takes into account the influence of the temperature profile on the ozone cross section. The temperature data are obtained from the radiosondes measurements performed at Ezeiza International Airport (34°30′S, 58°18′W), 27 km from DIAL station. The evolution of the stratospheric ozone profile is studied for different months. Results are compared with the data obtained by different satellites SAGE II, HALOE and GOME. The comparisons between our DIAL system and the satellite measurements show an agreement better than 20% for 20–35 km altitude range.

The Atmospheric Observatory of Austral Patagonia (OAPA) is a remote sensing site located near the Río Gallegos city in South Patagonia (51º 55'S, 69º 14'W), in subpolar region affected by the polar vortex. It is a convenient monitoring site of the atmosphere in the southern hemisphere especially for ozone studies. This site is operating a differential absorption lidar instrument (DIAL) for the measurement of ozone vertical distribution. This instrument is part of Network Data for Atmospheric Composition Change (NDACC). The altitude range of the ozone measurement is 14-45 km, which provides the opportunity to monitor the perturbations due to the passage of stratospheric polar air over Río Gallegos. Since 2005, systematic stratospheric ozone profile measurements have been carried on in this experimental site. The position of the station with respect to the polar vortex was analyzed from the use of equivalent latitude maps. We identified three major perturbation related to the ozone hole on the stratospheric ozone profile record in Río Gallegos: extension of the polar vortex towards the station during late winter, passage of the ozone hole over the station in middle spring and dilution process during late spring. All these three processes change the shape of the stratospheric ozone profile and produce variation in the total ozone column over the OAPA. These perturbations in the middle atmosphere induce change in solar UV radiation at ground surface of great importance for the health of people leaving in the area. In this article, we review the main conclusions regarding the observation of stratospheric ozone profiles measurements OAPA and surface UV radiation for the period 2005-2011.

As a part of environmental studies in the southern hemisphere, the CEILAP (UNIDEF-MINDEF) Lidar Division with the financial support of JICA (Japan International Cooperation Agency) and the collaboration of LATMOS, France mounted a ground based remote sensing site at Río Gallegos city (51º 36'S, 69º 19'W), at southern part of Argentina. The site called Atmospheric Observatory of Southern Patagonia (OAPA) has carried out systematic measurements of stratospheric ozone with lidar remote sensing techniques and passive sensors to measure solar UV irradiance from 2005. The Patagonian region is affected each spring season by the polar vortex which produces depletion in the total ozone column increasing the UV radiation that reaches the surface. In this work we report the results of total ozone column and UV radiation from different passive instruments as SAOZ and multichannel GUV-541 radiometer. A correlation between both instruments has been established to Río Gallegos in the period 2005-2011. Also we have taken into account the cloud cover that produces strong impact in the the amount of the UV radiation that reach the ground surface. We reported different cases of study where the OAPA site was inside of polar vortex.

Since June 2005, the CEILAP group with the support of JICA (Japan International Cooperation Agency) and cooperation with French LATMOS and Japanese researches has carried out systematic measurements of ozone profile and UV radiation in the southern part of Argentina (51°55'S, 69°14'W) using a Differential Absorption lidar (DIAL), this place has been called Atmospheric Observatory of Southern Patagonia (OAPA). After 2006 other products were retrieved in addition to the ozone profiles from the DIAL measurements, such as stratospheric aerosols and temperature profiles using the off ¬wavelength signal at 355 nm. This work presents the improved algorithm used to retrieve temperature from the lidar signals and unusual temperature measurements obtained in November 9. In this work we present the incorporation of a digital filter called Savitky ¬Golay. We have evaluated the cut off frequency of the filter in relation with number of point (N) as a function of cutoff frequency. Through extensive simulations we have found a power law representative of the filter behavior. Also we have incorporated a new climatology temperature profiles database calculated from the model MSISE¬90. As a part the evaluation of this algorithm we have detected an unusual temperature profiles on November 2009 due a depletion of the ozone density. We present the comparison of these profiles measured during November 13¬14 2009, compared with the NCEP mean profiles in Río Gallegos for the period 2005¬2011. We have found a warming in the higher stratosphere with a temperature anomaly of 25 K around 36 km when the temperature profile was compared with the NCEP mean profile.

Record-low ozone column densities (with a minimum of 212 DU) persisted over three weeks at the Río Gallegos NDACC (Network for the Detection of Atmospheric Composition Change) station (51.5° S, 69.3° W) in November 2009. Total ozone remained two standard deviations below the climatological mean for five consecutive days during this period. The statistical analysis of 30 years of satellite data from the Multi Sensor Reanalysis (MSR) database for Río Gallegos revealed that such a long-lasting low-ozone episode is a rare occurrence. The event is examined using height-resolved ozone lidar measurements at Río Gallegos, and observations from satellite and groundbased instruments. The computed relative difference between the measured total ozone and the climatological monthly mean shows reductions varying between 10 and 30% with an average decrease of 25 %. The mean absolute difference of total ozone column with respect to climatological monthly mean ozone column is around 75 DU. Extreme values of the UV index (UVI) were measured at the ground for this period, with the daily maximum UVI of around 13 on 15 and 28 November. The high-resolution MIMOSACHIM (Modélisation Isentrope du transport Méso-échelle de l'Ozone Stratosphérique par Advection) model was used to interpret the ozone depletion event. An ozone decrease of about 2 ppmv was observed in mid-November at the 550K isentropic level (~22 km). The position of Río Gallegos relative to the polar vortex was classified using equivalent latitude maps. During the second week of November, the vortex was over the station at all isentropic levels, but after 20 November and until the end of the month, only the 10 lower levels in the stratosphere were affected by vortex overpasses with ozone poor air masses. A rapid recovery of the ozone column density was observed later, due to an ozone rich filament moving over Río Gallegos between 18 and 24 km in the first two weeks of December 2009. Fil: Wolfram, Elian Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina Fil: Salvador, Jacobo Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina Fil: Orte, Pablo Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina Fil: D'elia, Raul Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina Fil: Godin Beekmann, S.. Centre National de la Recherche Scientifique; Francia Fil: Kuttippurath, J.. Centre National de la Recherche Scientifique; Francia Fil: Pazmiño, A.. Centre National de la Recherche Scientifique; Francia Fil: Goutail, F.. Centre National de la Recherche Scientifique; Francia Fil: Casiccia, C.. Universidad de Magallanes; Chile Fil: Zamorano, F.. Universidad de Magallanes; Chile Fil: Paes Leme, N.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; Brasil Fil: Quel, Eduardo Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina

International audience; Since 2005 the lidar division of CEILAP with researchers from France and Japan and with the financial support of JICA (Japanese International Cooperation Agency) conducted the installation of an experimental site measurements of atmospheric parameters in the Patagonian city of Rio Gallegos in southern Argentina. The measurement campaign period from 2005 to 2007 was called SOLAR (Stratospheric Ozone Lidar in ARgentina). The main objective was to study the evolution of the polar vortex on the continent and the stratospheric ozone profile between 15-45 km altitude. In 2006 we began to obtain other products such as aerosol content and temperature profile in the stratosphere. The determination of temperature measurements from Rayleigh scattering is an important remote sensing technique to obtain stratospheric profiles. This technique is applied to signals acquired by a lidar (Light Detection and Ranging) called DIAL (Differential Absorption Lidar) for determination of stratospheric ozone profiles. Currently the site is part of the UVO3Patagonia in collaboration with the laboratory of Ozone and UV Radiation in the city of Punta Arenas, Chile at 200 km, www.uvo3patagonia.com. In this paper we show the technique to measure temperature profiles in the stratosphere between 15-60 km altitude. The inversion temperature from photoncounting is detected from light scattered by the Rayleigh line at 355 nm generated from a Quantel YG-980 laser. An analysis of the errors involved in the inversion process and analysis of a case of study are shown for the period 2005-2007. The results presented in this paper are compared with measurements made by HIRDLS instrument (High Resolution Dynamics Limb Sounder) onboard the NASA AURA satellite platform, Ballon-borne and NCEP database.

International audience; The Satellite validation with lidar (VALID) project supports the long-term multi-mission validation of atmospheric chemistry and physics instruments with ground-based lidars. VALID involves lidar stations around the world measuring stratospheric ozone and temperature profiles, and tropospheric aerosol and cloud properties. Currently around ten thousand lidar profiles have been made available for validation purposes in VALID and its predecessor EQUAL (ENVISAT quality assessment with lidar). The satellite data under investigation here are the ozone and temperature profiles delivered by the MIPAS (Michelson interferometer for passive atmospheric sounding) and SCIAMACHY (Scanning imaging absorption spectrometer for atmospheric chartography) instruments as new algorithms have become available recently. We have collocated the satellite profiles with the lidar measurements and analysed the comparison results for dependence on several geophysical and instrument observational parameters. Results for the delta validation are presented for SCIAMACHY level 2 version 5.01 and for MIPAS level 2 version ORM (optimised retrieval model) 5.0x. For the SCIAMACHY validation, additional ozone sonde and microwave radiometer data have been included to enlarge the validation dataset. The consistent underestimation of the ozone concentrations by SCIAMACHY seen in version 3.01 is now removed. In the mid-latitudes, SCIAMACHY version 5.01 matches the validation instruments within 5% up to 38 km altitude. The cloud free data are more positively biased. In the polar regions, there is a variable bias ranging from -10% to +7% in the altitude range 15 to 35 km, increasing above (its magnitude depending on validation instrument). The cloud free data have a more enhanced negative bias. In the tropics, there is positive bias in SCIAMACHY v5.01 (5 to 23%) and the cloud free data appear to have a more positive bias (few percent). The large deviation at low altitudes could be due to sub-visual cirrus and will be further investigated in the future. Finally, with respect to the observation direction (corresponding to the scan angle), Eastern orientated profiles overall have a more negative bias than Western profiles For the MIPAS version 5.0x data, the ozone profiles match the lidar data very well over a large part of the compared altitudes. Deviations are seen at the bottom of the profiles starting with a positive bias when going down below the ozone maxima reaching up to +5%. In the tropics this bias changes sign when reaching the lower most altitudes and gets to -10%. At the highest altitudes there is a positive bias in the tropics (max. 2%) and in the mid-latitudes (max. 5%), whereas in the polar region there is an increasing underestimation from an altitude of 35 km (close to 0%) towards the top at 45 km (nearly 15%). The temperature data are mostly within 1 to 2 K from the lidar data. Looking at the different altitude axis, we cannot say that using the engineering altitudes gives a better performance than when using the corrected altitude axis. In fact, the comparison improves when introducing a shift of +500 m for the MIPAS data in the polar region and mid-latitudes (larger shift needed for the tropics). This is not seen in the ozone data and thus needs further study.

The validation of ozone profiles retrieved by satellite instruments through comparison with data from ground-based instruments is important to monitor the evolution of the satellite instrument, to assist algorithm development and to allow multi-mission trend analyses. In this study we compare ozone profiles derived from GOMOS night-time observations with measurements from lidar, microwave radiometer and balloon sonde. Collocated pairs are analysed for dependence on several geophysical and instrument observational parameters. Validation results are presented for the operational ESA level 2 data (GOMOS version 5.00) obtained during nearly seven years of observations and a comparison using a smaller dataset from the previous processor (version 4.02) is also included. The profiles obtained from dark limb measurements (solar zenith angle >107°) when the provided processing flag is properly considered match the ground-based measurements within ±2 percent over the altitude range 20 to 40 km. Outside this range, the pairs start to deviate more and there is a latitudinal dependence: in the polar region where there is a higher amount of straylight contamination, differences start to occur lower in the mesosphere than in the tropics, whereas for the lower part of the stratosphere the opposite happens: the profiles in the tropics reach less far down as the signal reduces faster because of the higher altitude at which the maximum ozone concentration is found compared to the mid and polar latitudes. Also the bias is shifting from mostly negative in the polar region to more positive in the tropics Profiles measured under "twilight" conditions are often matching the ground-based measurements very well, but care has to be taken in all cases when dealing with "straylight" contaminated profiles. For the selection criteria applied here (data within 800 km, 3 degrees in equivalent latitude, 20 h (5 h above 50 km) and a relative ozone error in the GOMOS data of 20% or less), no dependence was found on stellar magnitude, star temperature, nor the azimuth angle of the line of sight. No evidence of a temporal trend was seen either in the bias or frequency of outliers, but a comparison applying less strict data selection criteria might show differently.

International audience; The "Satellite validation with lidar" (VALID) project supports the long-term multi-mission validation of atmospheric chemistry and physics instruments with ground-based lidars. VALID involves lidar stations around the world measuring stratospheric ozone and temperature profiles, and tropospheric aerosol and cloud properties. Currently over 8000 lidar profiles have been made available for validation purposes in VALID and its predecessor EQUAL (ENVISAT quality assessment with lidar). The satellite data under investigation here are the ozone and temperature profiles delivered by the GOMOS (Global ozone monitoring by occultation of stars), MIPAS (Michelson interferometer for passive atmospheric sounding) and SCIAMACHY (Scanning imaging absorption spectrometer for atmospheric chartography) instruments. We have collocated these profiles with the lidar measurements and analysed the comparison results for dependence on several geophysical and instrument observational parameters, keeping a close look at the instruments’ performances during the seven years of data acquisition. Validation results will be presented for the operational ESA products and various scientific products.

Satellite sensors provide global measurements of ozone concentration that can be used to study the effects of the implementation of the Montreal Protocol. However, a key issue in deriving long-term ozone trends from successive satellite instruments is inter-comparability. Ground-based measurements offer continuous time series, but only at a few locations. The combination of ground-based measurements with satellite data is therefore an effective means to evaluate satellite instrument inter-comparability. In this study, we present validation results of ozone profiles from three atmospheric sensors onboard ENVISAT by comparison with lidar measurements. Results for the SCIAMACHY ozone profiles (version 3.01) show reasonable agreement with ground-based measurements (0 to -20%). The MIPAS full-resolution (version 4.61) dataset has good agreement with lidar (0 to 10%), whereas a small positive bias (up to 20%) was found for the MIPAS reduced-resolution prototype data. GOMOS dark-limb data (version 5.00) agree very well (0 ± 5%) with the correlative data, but underestimate ozone concentration at the polar regions. Fil: van Gijsel, J. A. E.. National Institute for Public Health and the Environment; Países Bajos Fil: Swart, D. P. J.. National Institute for Public Health and the Environment; Países Bajos Fil: Baray, J. L.. Université de la Reunión; Francia Fil: Claude, H.. Meteorological Observatory Hohenpeissenberg; Alemania Fil: Fehr, T.. European Space Agency; Italia Fil: von der Gathen, P.. Alfred Wegener Institute; Alemania Fil: Godin Beekmann, S.. Centre National de la Recherche Scientifique; Francia Fil: Hansen, G. H.. Norwegian Air Research Institute; Noruega Fil: Leblanc, T.. National Aeronautics and Space Administration; Estados Unidos Fil: McDermid, I. S.. National Aeronautics and Space Administration; Estados Unidos Fil: Meijer, Y. J.. European Space Agency; Italia Fil: Nakane, H.. National Institute for Environmental Studies; Japón Fil: Quel, Eduardo Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; Argentina Fil: Steinbrecht, W.. European Space Agency; Italia Fil: Strawbridge, K.B.. Centre for Atmospheric Research Experiments; Canadá Fil: Tatarov, B.. National Institute for Environmental Studies; Japón Fil: Wolfram, Elian Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; Argentina

The variability of total ozone and UV radiation from Total Ozone Mapping Spectrometer (TOMS) measurements is analyzed as a function of polar vortex occurrences over the southern subpolar regions during the 1997–2005 period. The analysis of vortex occurrences showed high interannual variability in the 40° S–60° S latitude band with a longitudinal asymmetry showing the largest frequencies over the 90° W–90° E region. The impact of vortex occurrences on UV radiation and ozone in clear sky conditions was determined from the comparison between the measurements inside the vortex and a climatology obtained from data outside the vortex over the studied period. Clear sky conditions were determined from TOMS reflectivity data. For measurements outside the vortex, clear sky conditions were selected for reflectivity values lower than 7.5%, while for measurements inside the vortex, a relaxed threshold was determined from statistically similar UV values as a function of reflectivity. UV changes and ozone differences from the climatology were analyzed in the 40° S–50° S and 50° S–60° S latitude bands during the spring period (September to November). The largest UV increases and ozone decreases, reaching ~200% and ~65%, respectively, were found in the 50° S–60° S latitude band in September and October. The heterogeneous ozone loss during vortex occurrences was estimated using a chemical transport model. The largest impact of vortex occurrences was found in October with mean UV increase, total ozone decrease and accumulated ozone loss in the 350–650 K range of, respectively, 47%, 30% and 57%. The region close to South America is the most affected by the Antarctic ozone depletion due to the combined effect of large number of vortex occurrences, lower cloud cover and large ozone decrease. This region would be the most vulnerable in case of cloud cover decrease, due to more frequent occurrence of ozone poor air masses during austral spring.

International audience; As part of environmental studies concerned with measurements of the stratospheric ozone layer, CEILAP has developed a new differential absorption lidar (DIAL) instrument. Since the initial construction of the first DIAL instrument, the Lidar Division of CEILAP has made important financial and scientific investments to upgrade this initial prototype. The new version has a bigger reception system formed by four Newtonian telescopes, each of 50 cm diameter, and a larger number of detection channels: four different wavelengths are detected simultaneously and six digital channels record the Rayleigh and Raman backscattered photons emitted by a ClXe excimer laser at 308 nm and the third harmonic of a Nd–YAG laser at 355 nm. A number of different changes have been made to increase the dynamic range of this lidar: a mechanical chopper was installed together with a gated photomultiplier in the high-energy detection channels to avoid the detector being overloaded by strong signals from lower atmospheric layers. This new version was installed inside a shelter, giving the possibility to make field campaigns outside CEILAP laboratories, for example the SOLAR campaign made in the Argentine Patagonian region during 2005 and 2006 spring periods. In this paper a full description of the instrument update is given. Intercomparisons with the ozone sonde and satellite platform instrument are presented. The results show agreement better than 10% in 16–38 km altitude range when the same airmasses are sampled. The comparison with five quasi-coincident sondes launched in Punta Arenas during spring 2005 shows good agreement between both types of measurement, with relative differences inside 1σ deviation of the lidar measurement. The comparison of the integral of height integrated lidar profiles with total ozone column measured with a Brewer photometer shows good agreement, with relative differences less than 10%.

International audience; As part of environmental studies of the southern atmosphere, the CEILAP Lidar Division in collaboration with the Service d'Aeronomie has developed a mobile differential absorption lidar capable of making precise and accurate measurements of the stratospheric ozone. The XeCl excimer laser emission at 308 nm is used as absorbed line in the DIAL technique and an Nd-YAG laser 355 nm third harmonic is employed as a reference wavelength. Six detected channels are used for stratospheric ozone retrieval, four of them in the high and low energy of the elastically backscattered signal of the emitted wavelengths and two corresponding to the first Stokes nitrogen Raman of the emitted wavelengths. Tropospheric Water Vapor profiles using Raman channels and Aerosol Backscatter profiles are also obtained. In this paper we present a detailed description of the instrument, a discussion of data analysis and the results of the first lidar-satellite inter-comparison of stratospheric ozone profiles measured with this instrument. We also present a description of the SOLAR campaign that will be held in the 2005 southern winter-spring period in Rio Gallegos (51° 55'S, 69° 14'W) with the objective of studying the ozone layer when the polar vortex crosses over the continental part of Argentina. This campaign will be supported by JICA (Japan International Cooperation Agency).

International audience; The evolution of total ozone and surface UV radiation over some stations in the southern region of South America and in Antarctica in relationship with polar vortex occurrences is analyzed using Total Ozone Mapping Spectrometer total ozone measurements and local surface UV data for the 1997–2003 period. The data are classified as a function of the position of the stations with respect to the polar vortex using equivalent latitude at 550 K isentropic level. The study of vortex occurrences showed that Ushuaia station (54.9°S) was located Å`40% of the cases in the edge of the vortex and 5% inside the vortex core during the winter-spring period. Concerning the Marambio (62.2°S) and Dumont d'Urville (66.4°S) stations, located on the shore of the Antarctic continent, the analysis shows a zonal asymmetry with respect to the center of the vortex. Marambio is located around 60% of the time inside the vortex, while Dumont d'Urville is predominantly at the edge of or outside the vortex. The evolution of the equivalent latitude of the stations in the anomalous 2002 winter presents a different behavior with respect to other years in the 1997–2003 period. The persistence of the vortex core above the stations is in average 1.8 days over Ushuaia and 7.1 days over Marambio in October during the 1997–2003 period with corresponding mean total ozone columns of 208.2 and 181.4 Dobson units, respectively. When the stations are inside the vortex, the total ozone columns are generally larger at Ushuaia than at Marambio in October during the 1997–2003 period. Finally, the impact of ozone-depleted air mass occurrences on ultraviolet radiation is evaluated by relating total ozone and UV erythemal dose measured at the stations. Twofold or threefold UV dose increases were reached in the 55°–65° southern latitude region during vortex overpasses, reaching maximum UV dose around 5 kJ/m2. The average increase of UV dose could be computed at the stations considered in the study when the measurement sampling and the number of vortex occurrences was sufficient. An average increase of 67.6% of the erythemal UV dose was found in October at Ushuaia over the years 1997, 1998, and 2000. This value is strongly weighted by vortex occurrences over the station in 2000. At Marambio an average UV increase of 47.4% was found over the years 1999 and 2000. Midlatitude stations like Comodoro Rivadavia (45.8°S) are generally little affected by vortex intrusions. Nevertheless, the maximum UV dose can increase by more than 50% when the vortex passes over the station.

International audience

International audience; Solar erythemal irradiance (directly related to the UV index) has been measured in Buenos Aires, Argentina, the largest populated city of the country. Similar data have also been obtained at Marambio Argentine Antarctic Base inside and outside the ozone hole region. In the latter case, the largest UV index during the 1996-1999 period, of value 10.2, is 22% lower than the corresponding one for Buenos Aires. However near its maximum, the integrated daily dose, which is of importance in the evaluation of the accumulated dose along a given period, is rather similar in both places. We thus propose to use also this quantity for solar risk forecast at high latitudes. Ozone profile data for Buenos Aires and Marambio Base are presented, as well as time series of erythemal irradiance and ozone total column. Ozone profiles have been determined using the differential absorption lidar technique (DIAL) in Buenos Aires during periods near maximum and minimum of ozone total column and near the maximum of solar intensity. Model calculations of the erythemal irradiance are done, incorporating these profiles as well as those commonly used in this type of analysis. The influence of different atmospheric parameters as well as of the ground albedo on the erythemal irradiance has been tested.

International audience; POLDER-1 on board the Japanese ADEOS platform has collected 8 months of data (October 1996 to June 1997). POLDER is a visible radiometer with multi-directional and polarization capabilities. These features allow to obtain information both on cloud thermodynamical phase and cloud altitude. The POLDER cloud algorithms are currently under validation. For cirrus clouds, a validation based on a comparison between cloud properties inferred from POLDER-1 data and cloud properties retrieved from a ground-based lidar network is currently under consideration. In this paper, preliminary comparisons between cloud altitude inferred from POLDER-1 and lidars are presented. These comparisons show an under-estimation of cloud altitude by POLDER-1 for optically thin clouds. A first theoretical analysis based on radiative transfer simulations allows to explain the difference between POLDER and lidar altitudes. Moreover, a preliminary comparison between thermodynamical cloud phase (liquid water / ice) obtained with POLDER-1 and cloud temperature inferred from radiosoundings and cloud altitudes shows that cirrus clouds at temperatures lower than −40°C are correctly identified as ice layers by POLDER-1