Measurements of the total ozone column using a Brewer spectrophotometer and TOMS and OMI satellite instruments over the Southern Space Observatory in Brazil

This paper presents 23 years (1992–2014) of quasi-continuous measurements of the total ozone column (TOC) over the Southern Space Observatory (SSO) in São Martinho da Serra, Brazil (29.26° S, 53.48° and 488 m altitude). The TOC was measured by a Brewer spectrometer, and the results are also compared to daily and monthly observations from the TOMS (Total Ozone Mapping Spectrometer) and OMI (Ozone Monitoring Instrument) satellite instruments. Analyses of the main interannual modes of variability computed using the wavelet transform method were performed. A favorable agreement between the Brewer spectrophotometer and satellite datasets was found. The seasonal TOC variation is dominated by an annual cycle, with a minimum of approximately 260 DU in April and a maximum of approximately 295 DU in September. The wavelet analysis applied in the SSO TOC anomaly time series revealed that the Quasi-Biennial Oscillation (QBO) modulation was the main mode of interannual variability. The comparison between the SSO TOC anomaly time series with the QBO index revealed that the two are in opposite phases

Impacts of the antartic ozone hole influence events over southern Brazil in October 2015

International audienceThe impact of the Antarctic Ozone Hole Influence over Southern Brazil in October 2015 was analyzed using daily mean data of the Total Column Ozone (TCO), Ultraviolet Index (UVI) and Radiative Cloud Fraction (RCF) from the Ozone Monitoring Instrument satellite instrument. Vertical profiles and fields of ozone content and Potential Vorticity available from the European Centre for Medium-Range Weather Forecast reanalysis, air masses backward trajectories from the HYbrid Single-Particle Lagrangian Integrated Trajectory model and channel 3 water vapor images from the Geostationary Operational Environmental Satellite GOES-13 were also analyzed. The five identified events showed an -7.4±2.3% average TCO reduction, leading to an +16.6±54.6% UVI increase even with a predominance of partly cloudy days. Other impacts were observed in the ozone profiles, where the most significant anomalies occurred from 650 K reaching 1.2 ppmv at the 850 K level. In the ozone fields at 700 K, the presence of a polar origin tongue was observed causing negatives anomalies between -0.2 and 0.4 ppmv in a transient system format forced with eastward-traveling Rossby waves passing through the Southern of Brazil and Uruguay

Avaliação do modelo BRAMS na formação de nevoeiro de radiação em ambiente com turbulência pouco desenvolvida BRAMS model evaluation with relation to formation of the radiation fog in the environment with not well-developed turbulence

Nevoeiro de radiação é normalmente precedido por forte resfriamento noturno. Em determinados eventos, a magnitude deste resfriamento é tão intensa que os modelos operacionais de previsão de tempo não conseguem representa-lo adequadamente. Simulações foram realizadas com o objetivo de reproduzir a formação do nevoeiro de radiação, observado na madrugada do dia 18 de abril de 2007. Foram testados parâmetros e parametrizações relacionados a turbulência disponíveis no modelo BRAMS versão 3.2. Para o cálculo do coeficiente de difusão vertical foram testados os esquemas de Mellor-Yamada e Smagorinsky, e para a razão entre os coeficientes de difusão vertical para escalares e para o momentum foram testados os valores 1 e 3. Os melhores resultados foram obtidos com o esquema de Mellor-Yamada e a razão 1 entre os coeficientes. A máxima taxa de resfriamento foi de -5,7ºC/10h e a taxa de umedecimento foi de 27,1%/10h, mas os dados observados indicaram valores de -8,8ºC/10h e 29%/10h, respectivamente. Com relação aos erros e taxas de resfriamento e umedecimento em superfície, as opções testadas geraram apenas pequenas melhoras nos resultados, mas foram suficientes para desenvolver o nevoeiro em superfície.<br>The radiation fog usually is preceded by a strong nocturnal cooling rate. Some times the observed cooling is so high that weather forecast models are not able to reproduce it accurately. Simulations were used to reproduce the formation of radiation fog at dawn on 18 April, 2007. Parameters and parameterizations related to turbulence available in BRAMS version 3.2 were tested. To calculate the vertical diffusion coefficients the Mellor-Yamada and Smagorinsky schemes were tested; and for the ratio of vertical diffusion coefficients between scalars and momentum the values 1 and 3 were tested. The best results were provided by the Mellor-Yamada parameterization scheme and when the ratio of vertical diffusion coefficients equal to 1. The maximum cooling rate obtained was -5,7ºC/10h and the moistening rate was -27,1%/10h, but the observed data showed values of -8,8ºC/10h and 29%/10h, respectively. In terms of surface cooling and moistening rate errors, the tested schemes led to small improvements in the results, but were sufficient to develop the fog over the surface