[1] We present validation studies of MLS version 2.2 upper tropospheric and stratospheric ozone profiles using ozonesonde and lidar data as well as climatological data. Ozone measurements from over 60 ozonesonde stations worldwide and three lidar stations are compared with coincident MLS data. The MLS ozone stratospheric data between 150 and 3 hPa agree well with ozonesonde measurements, within 8% for the global average. MLS values at 215 hPa are biased high compared to ozonesondes by $20% at middle to high latitude, although there is a lot of variability in this altitude region. Comparisons between MLS and ground-based lidar measurements from Mauna Loa, Hawaii, from the Table Mountain Facility, California, and from the Observatoire de HauteProvence, France, give very good agreement, within $5%, for the stratospheric values. The comparisons between MLS and the Table Mountain Facility tropospheric ozone lidar show that MLS data are biased high by $30% at 215 hPa, consistent with that indicated by the ozonesonde data. We obtain better global average agreement between MLS and ozonesonde partial column values down to 215 hPa, although the average MLS values at low to middle latitudes are higher than the ozonesonde values by up to a few percent. MLS

Abstract. The optical thickness of the atmosphere, x, was deduced from measurements of narrowband direct solar UV-B radiation. A measurement campaign was organized to obtain the radiation at three different sites, during the month of August 1999, using the same methods and instruments, in order to deduce the atmospheric optical thickness in the spectral UV-B range (280-320 nm). The three observation sites were chosen to cover a wide range of measurement conditions; located near the tropical Atlantic Ocean (

Abstract. 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 MIMOSA-CHIM (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 550 K 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.

Séries temporais de radiação UV-B, biologicamente ativa, obtidas em vários locais no Brasil, em Punta Arenas no Chile e em La Paz na Bolívia são apresentadas. O quadro atual de mudança atmosférica, principalmente a tendência global de redução no ozônio total, fez surgir na comunidade científica preocupações quanto a um possível aumento na intensidade da radiação ultravioleta (UV) solar na superfície terrestre. Nesse contexto, o Instituto Nacional de Pesquisas Espaciais-INPE opera uma rede de medidores do tipo Biômetro, radiômetros especialmente projetados para medir a radiação UV causadora de efeitos danosos à saúde humana, a radiação UV-B Eritema, desde o início dos anos 1990. Analisam-se neste trabalho as séries temporais de máxima dose diária de radiação UV-B Eritema obtidas com o Biômetro, estudando-se a variação sazonal e calculando-se o Índice UV. Os maiores valores do Índice UV são encontrados nas regiões de La Paz, Campo Grande e Natal. A radiação UV-B apresentou uma forte dependência da latitude geográfica e da altitude, conforme esperado. Os Índices UV atingiram valores próximos a 15 em La Paz, e acima de 12 em Natal e Campo Grande no período de verão. Também é apresentado o resultado de um experimento para medir a radiação UV-B difusa realizado em Cachoeira Paulista em 24 e 25 de novembro de 1998. A radiação difusa representa pelo menos 45% da radiação global para o UV-B Eritema. Palavras-chave:Radiação ultravioleta solar; UV-B; Atmosfera; Eritema; Biômetro. Brazil, and at La Paz, Bolívia and Punta Arenas, Chile, are presented THE SEASONAL VARIATION OF BIOLOGICALLY ACTIVE SOLAR UV-B RA-DIATION-Time series of biologically active UV-B radiation observed at sites in

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Abstract. The Antarctic ozone hole is a cyclical phenomenon that occurs during the austral spring where there is a large decrease in ozone content in the Antarctic region. Ozone-poor air mass can be released and leave through the Antarctic ozone hole, thus reaching midlatitude regions. This phenomenon is known as the secondary effect of the Antarctic ozone hole. The objective of this study is to show how tropospheric and stratospheric dynamics behaved during the occurrence of this event. The ozone-poor air mass began to operate in the region on 20 October 2016. A reduction of ozone content of approximately 23 % was observed in relation to the climatology average recorded between 1992 and 2016. The same air mass persisted over the region and a drop of 19.8 % ozone content was observed on 21 October. Evidence of the 2016 event occurred through daily mean measurements of the total ozone column made with a surface instrument (Brewer MkIII no. 167 Spectrophotometer) located at the Southern Space Observatory (29.42 • S, 53.87 • W) in São Martinho da Serra, Rio Grande do Sul. Tropospheric dynamic analysis showed a post-frontal high pressure system on 20 and 21 October 2016, with pressure levels at sea level and thickness between 1000 and 500 hPa. Horizontal wind cuts at 250 hPa and omega values at 500 hPa revealed the presence of subtropical jet streams. When these streams were allied with positive omega values at 500 hPa and a high pressure system in southern Brazil and Uruguay, the advance of the ozone-poor air mass that caused intense reductions in total ozone content could be explained.

Abstract. Ozone is one of the chemical compounds that form part of the atmosphere. It plays a key role in the stratosphere where the “ozone layer” is located and absorbs large amounts of ultraviolet radiation. However, during austral spring (August–November), there is a massive destruction of the ozone layer, which is known as the “Antarctic ozone hole”. This phenomenon decreases ozone concentration in that region, which may affect other regions in addition to the polar one. This anomaly may also reach mid-latitudes; hence, it is called the “secondary effect of the Antarctic ozone hole”. Therefore, this study aims to identify the passage of an ozone secondary effect (OSE) event in the region of the city of Santa Maria – RS (29.68∘ S, 53.80∘ W) by means of a multi-instrumental analysis using the satellites TIMED/SABER, AURA/MLS, and OMI-ERS. Measurements were made in São Martinho da Serra/RS – Brazil (29.53∘ S, 53.85∘ W) using a sounding balloon and a Brewer Spectrophotometer. In addition, the present study aims to describe and analyse the influence that this stratospheric ozone reduction has on temperatures presented by these instruments, including data collected through the radio occultation technique. The event was first identified by the AURA/MLS satellite on 19 October 2016 over Uruguay. This reduction in ozone concentration was found by comparing the climatology for the years 1996–1998 for the state of Rio Grande do Sul, which is close to Uruguay. This event was already observed in Santa Maria/RS-Brazil on 20 October 2016 as presented by the OMI-ERS satellite and the Brewer Spectrophotometer. Moreover, a significant decrease was reported by the TIMED/SABER satellite in Uruguay. On 21 October, the poor ozone air mass was still over the region of interest, according to the OMI-ERS satellite, data from the sounding balloon launched in Santa Maria/RS-Brazil, and measurements made by the AURA/MLS satellite. Furthermore, the influence of ozone on the stratosphere temperature was observed during this period. Despite a continuous decrease detected in height, the temperature should have followed an increasing pattern in the stratospheric layer. Finally, the TIMED/SABER and OMI-ERS satellites showed that on 23 October, the air mass with low ozone concentration was moving away, and its layer, as well as the temperature, in the stratosphere was re-established. Keywords. Atmospheric composition and structure (middle atmosphere – composition and chemistry; instruments and techniques)

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