Entre os elementos do sistema climático que influenciam as atividades socioeconômicas, a precipitação apresenta papel fundamental em áreas tropicais. Regiões como África e América do Sul apresentam uma escassez considerável de observações desta variável, uma vez que a rede de estações meteorológicas não cobre sistematicamente todo o território. Neste contexto, produtos de múltiplos sensores, algoritmos e modelos climáticos são utilizados cada vez mais para análises dos elementos atmosféricos, do clima e da influência da precipitação nas características ambientais. Assim, há uma demanda crescente de validação de produtos orbitais e de simulações numéricas de forma a dar suporte aos estudos da distribuição espacial e temporal da precipitação. Este estudo tem como objetivo principal analisar os dados mensais de precipitação do produto Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS) e verificar sua similaridade com os dados de estações meteorológicas do conjunto de informações do Centro de Previsão de Tempo e Estudos Climáticos (CPTEC) do Instituto Nacional de Pesquisas Espaciais (INPE) e do Instituto Nacional de Meteorologia (INMET) para o território brasileiro para os anos de 1981 a 2011. Para avaliar o CHIRPS, foram utilizados dados de 183 estações meteorológicas do INMET/CPTEC. Os resultados indicam que todas as regiões políticas do Brasil apresentaram correlação linear alta entre as informações do INMET/CPTEC e CHIRPS (95,4 %), ainda, quando consideramos toda a área do Brasil, a correlação linear média entre os dados é de 97%, significativa a p<0,05, teste t-student. Espacialmente, o noroeste do estado do Amazonas e o sudoeste do Pará apresentaram as maiores diferenças entre o conjunto de dados. As estimativas do CHIRPS ajustadas linearmente com os dados do INMET/CPTEC apresentaram uma concordância mais acentuada.

In the Brazilian savannas (Cerrado biome) fires are natural and a tool for shifting land use; therefore, temporal and spatial patterns result from the interaction of climate, vegetation condition and human activities. Moreover, orbital sensors are the most effective approach to establish patterns in the biome. We aimed to characterize fire, precipitation and vegetation condition regimes and to establish spatial patterns of fire occurrence and their correlation with precipitation and vegetation condition in the Cerrado. The Cerrado was first and second biome for the occurrence of burned areas (BA) and hotspots, respectively. Occurrences are higher during the dry season and in the savanna land use. Hotspots and BA tend to decrease, and concentrate in the north, but more intense hotspots are not necessarily located where concentration is higher. Spatial analysis showed that averaged and summed values can hide patterns, such as for precipitation, which has the lowest average in August, but minimum precipitation in August was found in 7 % of the Cerrado. Usually, there is a 2–3-month lag between minimum precipitation and maximum hotspots and BA, while minimum VCI and maximum hotspots and BA occur in the same month. Hotspots and BA are better correlated with VCI than precipitation, qualifying VCI as an indicator of the susceptibility of vegetation to ignition.

Ozone events in South America might be triggered by increasing air temperatures and dry conditions, leading to vulnerable population exposure. The current air quality standards and attention levels in São Paulo state, Brazil, are 40% higher and 25% higher, respectively, than the limits recommended by the World Health Organization (WHO). We simulated an extreme ozone event in the São Paulo megacity using the Weather Research and Forecast/Chemistry model during an extreme event characterized by positive anomalies of air temperature and solar radiation. Results were evaluated using the different air quality limits from São Paulo state and the WHO, also with socioeconomic vulnerability data from the Brazilian census and cost analysis for the public health system from the extreme episode. More than 3 million people in vulnerability conditions, such as low income and families with an above-average percentage of children, live in areas where ozone concentrations exceeded the attention levels of the WHO during the episode, which is ignored by the lenient SP state environmental laws. WHO air quality guidelines must be adopted urgently in developing nations in order to provide a more accurate basis for cost analysis and population exposure, particularly the for vulnerable population groups.

Fire occurrence is a major disturbance in the Brazilian Cerrado, which is driven by both natural and anthropogenic activities. Despite increasing efforts for monitoring the Cerrado, a biome-scale study for quantifying and understanding the variability of fire emissions is still needed. We aimed at characterizing and finding trends in Particulate Matter with diameter less than 2.5 µm (PM_2.5) fire emissions in the Brazilian Cerrado using the PREP-CHEM-SRC emissions preprocessing tool and Moderate Resolution Imaging Spectroradiometer (MODIS) active fires datasets for the 2002–2017 period. Our results showed that, on average, the Cerrado emitted 1.08 Tg year⁻¹ of PM_2.5 associated with fires, accounting for 25% and 15% of the PM_2.5 fire emissions in Brazil and South America, respectively. Most of the PM_2.5 fire emissions were concentrated in the end of the dry season (August, 0.224 Tg month⁻¹ and September, 0.386 Tg month⁻¹) and in the transitional month (October, 0.210 Tg month⁻¹). Annually, 66% of the total emissions occurred over the savanna land cover; however, active fires that were detected in the evergreen broadleaf land cover tended to emit more than active fires occurring in the savanna land cover. Spatially, each 0.1° grid cell emitted, on average, 0.5 Mg km⁻² year⁻¹ of PM_2.5 associated with fires, but the values can reach to 16.6 Mg km⁻² year⁻¹ in a single cell. Higher estimates of PM_2.5 emissions associated with fires were mostly concentrated in the northern region, which is the current agricultural expansion frontier in this biome. When considering the entire Cerrado, we found an annual decreasing trend representing -1.78% of the annual average PM_2.5 emitted from fires during the period analyzed, however, the grid cell analysis found annual trends representing ± 35% of the annual average PM_2.5 fire emissions.

Complexity and predictability of daily precipitation in a tropical semi-arid region (Ceará State, Brazil) is assessed by applying entropy concepts. Precipitation regimes in that region depend on several dynamical forcings, the most important being the displacement and activity of the Inter-tropical Convergence Zone in the Atlantic Ocean. Topography is another important factor that influences the spatial distribution of rainfall in the region. A hierarchical approach based on sequences of events of different lengths is used to estimate complexity of daily precipitation records. It is shown that precipitation in Ceará exhibit more random than periodic sequences, which indicates a large degree of complexity. Nevertheless, there is indication of potentially inherent rules in the precipitation time-series that could ultimately improve prediction on time-scales between 9–11 days. It is suggested that synoptic-scale disturbances (1–8 days) represent important sources of rules in the precipitation regimes in this region.