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[1] The optical thickness of the atmosphere, t at , was deduced from measurements of narrowband direct solar UV-B (280 -320 nm) radiation. This is the radiation that is strongly absorbed in the stratosphere by ozone, especially near the lower limit wavelength of these measurements, 306.3 nm. Measurement campaigns were organized to obtain radiation data at different sites, for different kinds of aerosol, using the same methods and instruments, in order to deduce the atmospheric optical thickness for different atmospheric conditions. The measurements were made with a Brewer spectrophotometer at each site. This instrument measures also the atmospheric ozone and sulphur dioxide columns, and therefore it is possible to deduce the aerosol optical thickness, t ae . The possibility of additional absorptions in the UV-B band, especially formaldehydes, is investigated. Two data sets are examined: C. Grande and S. Paulo. A large percentage of the data show that the wavelength dependence of the aerosol optical thickness is one that appears to increase with wavelength. In other words, the difference between the absolute values at 320.1 and 306.3 nm, is positive for the majority of cases. However, this difference is not always larger than the uncertainty/error of the measurement. This intriguing result opposes the Angstrom law, applicable to a much larger dynamic range in wavelength. For the C. Grande data (with generally larger values of optical thickness), the difference is positive in 16 out of 19 cases, but there are only 4 cases when the difference is larger than the error. For the S. Paulo morning data, however, the opposite is true. The difference is positive with only one exception, and there are 13 cases out of 17 where the difference is larger than the error.

Abstract. This paper presents 23 years 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.

a b s t r a c tThe use of ethanol as fuel has encouraged many countries to improve their production processes. However, costs related to its current production model have been occasionally mentioned as a disadvantage to the use of this biofuel. One of the main costs is the energy expenditure for an effective distillation of the fermented ethanol wort, to result a final product called hydrous ethanol (about 95% by volume of ethanol in water). A promising alternative is the use of ethanol fuel with high fractions of water (above 5% by volume), the so-called wet ethanol, which would reduce the energy cost of production during the distillation. Thus, this study proposes the development of a mathematical model that, along with experimental data, is able to predict the effect that the use of wet ethanol has on the performance of internal combustion engines. In order to do so, along with commercial hydrous ethanol, blends were prepared with the following volume fractions of water: 10% (E90W10), 20% (E80W20), 30% (E70W30) and 40% (E60W40). Tests were performed considering two engine operating conditions: (a) fixed ignition timing and (b) adjusted ignition timing for maximum engine torque. The model was able to successfully simulate the gradients of pressure and temperature in the cylinder and it showed good ability to predict engine performance based on the variations of power, torque, conversion efficiency, and specific fuel consumption. Except for the specific fuel consumption, where the estimated error for variations was greater than 20%, the estimates for the other performance parameter presented relative errors lower than 7%. For all tests, the relative error was lower than 13%. The gradual increase of specific fuel consumption was associated with the increasing water content. Among the fuels tested, E70W30 showed the best performance, followed by the E80W20 blend; both were more efficient than the commercial ethanol.