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)

This study investigates a summer heat wave (HW) associated with downslope winds (DWs) affecting the central region of the state of Rio Grande do Sul (RS), Brazil. The temporal evolution of both phenomena is analyzed in the atmospheric boundary layer (ABL) using a combination of micrometeorological and rawinsonde data. For spatial characterization, ERA-5 reanalysis data are used. The HW covered a large area in southern Brazil, Argentina, and Paraguay. The main features of the HW were locally enhanced in the central region of RS by the development of DWs. The establishment of DWs near the surface depends on the dynamics of the ABL and local topographic features. The results showed that DWs that occurred during the HW contributed to the extreme temperatures and were associated with strong northerly winds, low relative humidity, and a drop in the dew points. Together, these extreme events influenced the turbulent and mean flow patterns of the ABL. The increase in turbulent activity associated with the warming of the ABL favored enhanced growth of morning ABL, while at night the simultaneous effects of radiative and turbulence cooling inhibited the formation of a strong stable ABL. The analysis highlights the complex interplay of synoptic and local factors associated with DWs and HW.

The strategy for assessing simulations produced by climate models established as part of the Atmospheric Model Intercomparison Project (AMIP) delivers an outline for model analysis, verification/validation, and intercomparison. Numerical models are continuously being developed to find the best representation for the amount and distribution of precipitation in Brazil to improve the country’s precipitation forecast. This article describes the key features of the Brazilian Global Atmospheric Model (BAM) (developed by the Center for Weather Forecasting and Climate Studies of the National Institute for Space Research (CPTEC/INPE)) and analyses of its performance for annual rainfall climate simulations. This study considered the representation of the annual precipitation in Brazil mainly during the rainy season in the central part of Brazil by the BAM. The model was run over the 1990 to 2015 period using spectral Eulerian model dynamics with a 70-horizontal resolution of approximately 1.0∘× 1.0∘ and 42 vertical sigma levels. The analysis was divided into two stages: the annual precipitation and the rainy season precipitation. Model precipitation analyses were performed using statistical methods, such as the mean and standard deviation, comparing modeled data with observed data from two datasets, data from the XAV (observed data from INMET, ANA, and DAEE), and the Climate Prediction Center (CPC). In general, the BAM model simulations reasonably replicated the configuration of the spatial distribution of precipitation in the Brazilian territory almost entirely, especially compared with the XAV. The accumulated precipitation in the southern region presented great variation, accumulating from 750 mm year−1 in the extreme south to 1750 mm year−1 in the north of this region. Average values of the BAM accumulated precipitation ranged from 1000 to 2000 mm year−1, within the expected average, compared to observed values of 750–1500 mm year−1 (CPC and XAV, correspondingly). Although there was an underestimation of the accumulated precipitation by the model, the model reasonably reproduced the precipitation during the rainy season. The performed assessment identified model aspects that need to be improved.

<p>The South Atlantic Convergence Zone (SACZ) has been subjectively defined as a band of cloudiness from the intense convection over the Amazon basin extending toward southeast Brazil, that is one of the main components of the South American monsoon system. The SACZ represents a region of deep convection, causing heavy precipitation events in the region for at least 4 days. The precipitation that occurs during the months of October to March is essential for maintaining the climate of the Southeast, Midwest and North of Brazil. Because of this, SACZ is an important climatological feature of the austral summer in Brazil. The representation of SACZ precipitation is complex and the need for numerical models calibrated according to the atmospheric conditions of the region to be analyzed is increasing. Thinking on this, researchers from the National Institute for Space Research (INPE) have been developing the Brazilian Global Atmospheric Model (BAM), in order to improve weather and climate forecasting simulations and climate change studies. The BAM is a semi-implicit Eulerian spectral model (BAMb-SL version, approximately 1.0° x 1.0° of horizontal resolution). With the importance of SACZ in mind and the need to improve its prediction, this study aims to analyze the climatology of SACZ through simulations of the BAM model in the period between 1992 to 2015, in which 156 SACZ event were recorded. BAM simulations will be compared with observed and reanalysis data, in order to evaluate the performance of BAM simulating ZCAS. The data that will used in this study is the BAM simulations of the variables precipitation, 200-hPa wind, outgoing longwave radiation, and 850-hPa specific humidity, daily observed precipitation data from the dataset organized and interpolated to 0.25° x 0.25° grid by Alexandre C. Xavier and available on the website https://utexas.app.box.com/v/xavier-etal-ijoc-data, outgoing longwave radiation from Climate Prediction Center do National Oceanic and Atmospheric Administration (CPC – NOAA, spatial resolution 0.75º x 0.75º) and 200-hPa wind and specific humidity at the level of 850-hPa from ERA5 of the ECMWF (spatial resolution 0.30º x 0.30º). The analyzes were obtained from statistical methods, with the mean and monthly standard deviation of the accumulated precipitation, and mean monthly of the outgoing longwave radiation, 200-hPa wind and specific humidity at the level of 850hPa, applied which data sets that were explained. Overall, the initial results showed a good agreement between the data sets. The average accumulated precipitation presented by the model simulations represented the spatial distribution of precipitation, in the central region of the Brazil were characterizing the SACZ, but these values were lower compared to those observed. The lowest OLR values presented by the reanalyses on the central region of the Brazil characterizes the SACZ position, as well as the BAM simulations. The other variables are still being analyzed. With the results obtained untill now, it is possible to say that, although the magnitude of each variable is underestimated, the simulations showed a good level of agreement between the data sets in the spatial representation of the variables analyzed in the 156 SACZ events.</p>