Débora Souza Alvim

Ozone precursors for the São Paulo Metropolitan Area.

Ozone represents the main atmospheric pollutant in the São Paulo Metropolitan Area (SPMA). In this region, its concentration exceeds the national air quality standards for several days out of the year. Ozone is a secondary pollutant and is a product of VOCs, NO(x), and sunlight. Thus, it is very difficult to elaborate efficient strategies for its reduction. Computational simulations may provide an interesting alternative to evaluate the many factors that affect ozone formation. In this study, the trajectory model OZIPR was used together with the SAPRC chemical mechanism to determine the incremental reactivity scale for VOCs in the SPMA. VOC input data were obtained from two campaigns that were performed in the studied area in 2006. Values for CO, NO(x), and meteorological parameters were obtained by automatic monitors. Five base-cases were created to verify the variation in maximum ozone concentration and thus determine the ozone formation potential of each VOC. NO(x) and VOC emissions were independently and simultaneously reduced by 5, 10, 20, and 30% to verify variations in ozone formation. With the simulator output data, ozone isopleths charts were generated for the city of São Paulo. Analysis of the obtained results shows that the most frequent compounds found among the ten main ozone precursors in São Paulo, using the reactivity scales created from the five base-cases, were: formaldehyde, acetaldehyde, propene, isoprene, cis-2-butene, and trans-2-butene, with formaldehyde being always the main ozone precursor compound. The simulations also show that an efficient strategy to decrease ozone concentrations in the SPMA would be to reduce total VOC emissions. The same strategy is not possible for NO(x), as the reduction of these pollutants would increase ozone concentrations.

Estudos dos compostos orgânicos voláteis precursores de ozônio na cidade de São Paulo

O ozonio e o principal problema de poluicao do ar na cidade de Sao Paulo. Este estudo, que foi realizado em uma estacao de monitoramento da qualidade do ar da Companhia de Tecnologia de Saneamento Ambiental (CETESB), enfoca a elucidacao dos principais compostos orgânicos volateis precursores de ozonio na atmosfera paulistana. Foram coletadas 36 amostras nos meses de agosto e setembro de 2006, nos quais o consumo de etanol era de aproximadamente 50% nesta epoca. Foram quantificadas 69 especies de compostos orgânicos volateis, nos quais os dez compostos mais importantes na formacao de O3 foram: 1-buteno (6,8%), eteno (6,5%), formaldeido (6,1%), acetaldeido (5,5%), tolueno (4,8%), 1-etil-4-metilbenzeno (3,7%), trans-2-penteno (3,7%), propeno (3,7%), trans-2-buteno (3,5%) e 1-metilciclopenteno (3,5%). As classes mais abundantes em concentracao no ar foram: alcanos (45%), alcenos (26%), aromaticos (14%), aldeidos (13%) e alcadienos (2%).

Measurements of emissions from motorcycles and modeling its impact on air quality

The increase in the number of motorcycles in large Brazilian cities is due to several factors such as traffic, low cost, mobility, few parking lots and the low efficiency of public transportation, becoming an important factor in air quality deterioration. In this context, vehicle emissions monitoring is essential to understand the contribution to air pollution as a whole. In this scenario, the emissions were sampled on a motorcycle dynamometer test bench and analyzed by gas chromatography and on-line analyzers according to the EC/97/24 standard (European Commission). Emissions from motorcycles using commercial gasoline (with 22% of ethanol) were used in combination with meteorological data and ambient air pollutants for Rio de Janeiro City (Brazil) during the Winter of 2011, using the trajectory model OZIPR (Ozone Isopleth Package for Research) and the chemical model SAPRC99 (State-wide Air Pollution Research Centre) to assess the impact on the ozone formation in the troposphere of Rio de Janeiro for the next several years. The results indicate that ozone levels will exceed the established limits by national legislation within three years. The study also showed that pollutant emission rates stay in agreement with emissions recommended by the Brazilian legislation for all phases. The increase in ozone concentration occurs due to high emissions of reactive volatile organic compounds in an atmosphere with high levels of nitrogen oxides (NOx). Given this scenario, additional measures are necessary to manage emissions from mobile sources in the future.

The Brazilian Global Atmospheric Model (BAM): Performance for Tropical Rainfall Forecasting and Sensitivity to Convective Scheme and Horizontal Resolution

AbstractThis article describes the main features of the Brazilian Global Atmospheric Model (BAM), analyses of its performance for tropical rainfall forecasting, and its sensitivity to convective scheme and horizontal resolution. BAM is the new global atmospheric model of the Center for Weather Forecasting and Climate Research [Centro de Previsao de Tempo e Estudos Climaticos (CPTEC)], which includes a new dynamical core and state-of-the-art parameterization schemes. BAM’s dynamical core incorporates a monotonic two-time-level semi-Lagrangian scheme, which is carried out completely on the model grid for the tridimensional transport of moisture, microphysical prognostic variables, and tracers. The performance of the quantitative precipitation forecasts (QPFs) from two convective schemes, the Grell–Devenyi (GD) scheme and its modified version (GDM), and two different horizontal resolutions are evaluated against the daily TRMM Multisatellite Precipitation Analysis over different tropical regions. Three main r...

Evaluation of TRMM/GPM Blended Daily Products over Brazil

The precipitation estimates from the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (named TMPA and TMPA-RT for the near real-time version) are widely used both in research and in operational forecasting. However, they will be discontinued soon. The products from the Integrated Multi-satellite Retrievals for Global Precipitation Measurement (IMERG) and The Global Satellite Mapping of Precipitation (GSMaP) are analyzed as potential replacements for TMPA products. The objective of this study is to assess whether the IMERG and/or GSMaP products can properly replace TMPA in several regions with different precipitation regimes within Brazil. The validation study was conducted during the period from 1st of April, 2014 to the 28th of February, 2017 (1065 days), using daily accumulated rain gauge stations over Brazil. Six regions were considered for this study: five according to the precipitation regime, plus another one for the entire Brazilian territory. IMERG-Final, TMPA-V7 and GSMaP-Gauges were the selected versions of those algorithms for this validation study, which include a bias adjustment with monthly (IMERG and TMPA) and daily (GSMaP) gauge accumulations, because they are widely used in the user’s community. Results indicate similar behavior for IMERG and TMPA products, showing that they overestimate precipitation, while GSMaP tend to slightly underestimate the amount of rainfall in most of the analyzed regions. The exception is the northeastern coast of Brazil, where all products underestimate the daily rainfall accumulations. For all analyzed regions, GSMaP and IMERG products present a better performance compared to TMPA products; therefore, they could be suitable replacements for the TMPA. This is particularly important for hydrological forecasting in small river basins, since those products present a finer spatial and temporal resolution compared with TMPA.

COMPOSTOS ORGÂNICOS VOLÁTEIS: PRINCIPAIS PRECURSORES DE OZÔNIO NA CIDADE DE SÃO PAULO

The main air quality problems registered in the in the city of Sao Paulo are caused by ozone (O 3 ) concentrations. This study, which was carried out in the Brazilian Basic Sanitation Engineering Company (CETESB) monitoring station of air quality located in the University of Sao Paulo - USP, focused on the elucidation of the main volatile organic compounds (VOCs) ozone precursors in Sao Paulo atmosphere between January to December 2006. Seventy-eight samples of air were collected during the study period, which the ten most important compounds in the formation of O3 were but-1-ene (12%), propene (10%), ethylene (8%), p-xylene (7% ) buta-1,3-diene (6%), 1-ethyl-4-methylbenzene (4%), isoprene (4%), trans-but-2-ene (4%), 2-methyl-but-2-ene (4%) and cis-but-2-ene (3%). The most abundant classes concentration in the air were alkanes (45%), alkenes (26%), and aromatics (14%), aldehydes (13%) and alkadienes 2%.