No abstract

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.

Abstract. 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.

Abstract:The objective of this study was to analyze the spatial and temporal distribution of burned areas in Rondônia State, Brazil during the years 2000 to 2011 and evaluate the burned area maps. A Linear Spectral Mixture Model (LSMM) was applied to MODIS surface reflectance images to originate the burned areas maps, which were validated with TM/Landsat 5 and ETM+/Landsat 7 images and field data acquired in August 2013. The validation presented a correlation ranging from 67% to 96% with an average value of 86%. The lower correlation values are related to the distinct spatial resolutions of the MODIS and TM/ETM+ sensors because small burn scars are not detected in MODIS images and higher spatial correlations are related to the presence of large fires, which are better identified in MODIS, increasing the accuracy of the mapping methodology. In addition, the 12-year burned area maps of Rondônia indicate that fires, as a general pattern, occur in areas that have already been converted to some land use, such as vegetal extraction, large animal livestock areas or diversified permanent crops. Furthermore, during the analyzed period, land use conversion associated with climatic events significantly influenced the occurrence of fire in Rondônia and amplified its impacts.

Deforestation in the Brazilian Amazon is related to the use of fire to remove natural vegetation and install crop cultures or pastures. In this study, we evaluated the relation between deforestation, land-use and land-cover (LULC) drivers and fire emissions in the Apyterewa Indigenous Land, Eastern Brazilian Amazon. In addition to the official Brazilian deforestation data, we used a geographic object-based image analysis (GEOBIA) approach to perform the LULC mapping in the Apyterewa Indigenous Land, and the Brazilian biomass burning emission model with fire radiative power (3BEM_FRP) to estimate emitted particulate matter with a diameter less than 2.5 µm (PM2.5), a primary human health risk. The GEOBIA approach showed a remarkable advancement of deforestation, agreeing with the official deforestation data, and, consequently, the conversion of primary forests to agriculture within the Apyterewa Indigenous Land in the past three years (200 km2), which is clearly associated with an increase in the PM2.5 emissions from fire. Between 2004 and 2016 the annual average emission of PM2.5 was estimated to be 3594 ton year−1, while the most recent interval of 2017–2019 had an average of 6258 ton year−1. This represented an increase of 58% in the annual average of PM2.5 associated with fires for the study period, contributing to respiratory health risks and the air quality crisis in Brazil in late 2019. These results expose an ongoing critical situation of intensifying forest degradation and potential forest collapse, including those due to a savannization forest-climate feedback, within “protected areas” in the Brazilian Amazon. To reverse this scenario, the implementation of sustainable agricultural practices and development of conservation policies to promote forest regrowth in degraded preserves are essential.