Browsing by Author "Salvador, J."
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Item Extreme sunbathing: three weeks of small total O3 columns and high UV radiation over the southern tip of South America during the 2009 Antarctic O3 hole season(American Geophysical Union, 2010-07-27) Laat, A.T.J. de; Van der A., R.J.; Alaart, M.A.F.; Van Wheele, M.; Benítez, G.C.; Casiccia, Claudio; Paes Leme, N.M.; Quel, E.; Salvador, J.; Wolfram, E.This paper presents an analysis of satellite and groundbased measurements of total O3 columns and the UV index of a unique event during the 2009 Antarctic O3 hole season. From 11 to 30 November 2009 the Antarctic vortex was located just south of the southern tip of South America rather than at its climatological position over Antarctica. Analysis of 30 years of assimilated total O3 column and UV index measurements shows that this 20‐day event was unique in the history of the ozone hole for these latitudes. During this period, small total O3 columns and large UV index values were observed over the southern tip of South America. Comparison of ground‐based and satellite measurements of total O3 columns and satellite based calculations of the UVI index – never designed nor validated for such extreme Southern Hemisphere conditions – show excellent agreement.Item The unusual persistence of an ozone hole over a southern mid-latitude station during the Antarctic spring 2009: a multi-instrument study(Istituto Nazionale di Geofisica e Vulcanologia (INGV), 2012) Wolfram, E. A.; Salvador, J.; Orte, F.; D'Elia, R.; Godin-Beekmann, S.; Kuttippurath, J.; Pazmiño, A.; Goutial, F.; Casiccia, Claudio; Zamorano, Felix; Paes Leme, N.; Quel, E. J.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 (Modelisation 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.