Recuperação de temperatura de superfície terrestre da radiância termal coletada pelo sensor TIRS/Landsat 8 : aplicações de medidas de campo e laboratório

A temperatura da superfície terrestre (Land surface temperature - LST) é um importante parâmetro na investigação de mudanças ambientais e climáticas em várias escalas. Entretanto, estimar esse parâmetro da radiação emitida na região do infravermelho termal (TIR) é uma tarefa difícil, pois as radiações medidas pelos sensores dos satélites são fortemente afetadas por efeitos atmosféricos. Todos métodos de recuperação de LST requerem validação com medidas de campo. Porém, a validação deste tipo de dado é um desafio, visto que a LST muda rapidamente no tempo e as medidas devem ser realizadas em conjunto com a passagem do sensor. Além disso, a maioria das metodologias são desenvolvidas e testadas com foco no hemisfério norte. Tendo em vista que maneiras operacionais de se obter LST devem ser constantemente investigadas, o objetivo desta pesquisa foi estudar o efeito do uso de medidas de emissividade de laboratório tomadas com base em temperaturas na determinação da LST a partir de dados de sensoriamento remoto orbital. Ademais, pretendeu-se realizar uma análise comparativa entre os algoritmos single-channel mais recentes existentes na literatura, aplicados à banda 10 (10,6-11,19 μm) do Landsat 8 TIRS. Os algoritmos considerados foram: Single-Channel Generalizado (SCG), Improved Single-Channel (ISC) e Improved Mono-Window (IMW). Um campo de dunas costeiras foi escolhido como área de estudo. Dois conjuntos de medidas de emissividade de laboratório foram construídos com amostras de campo em diferentes temperaturas com uso de um Fourier Transform Infrared (FT-IR). Dados de emissividade e temperatura foram obtidos na área de estudo concomitamente com a passagem do sensor. A equação de transferência radiativa (Radiative Transfer Equation - RTE) com parâmetros de perfis atmosféricos globais foi testada como forma de validação de dados. Uma variação de aproximadamente 2% na emissividade em relação à temperatura foi observada, podendo ser negligenciada. O FT-IR apresenta limitações quanto ao período para adquirir estabilidade, porém respeitando esta limitação e realizando abordagem correta de calibração, medidas laboratoriais podem atingir ótima acurácia e substituir a validação de campo. Bibliotecas espectrais disponíveis de emissividade demonstraram ser também uma alternativa válida. Todos métodos single-channel avaliados são adequados para obter LST; no entanto, o ISC forneceu resultados superiores em todas as análises, produzindo maior R² (0,99978) e menor RMSE (0.019) em relação aos demais.Land surface temperature (LST) is an important parameter in the investigation of environmental and climatic changes at various scales. However, estimating this parameter from the radiation emitted in the thermal infrared (TIR) region is a difficult task because the radiation measured by the satellite sensors is strongly affected by atmospheric effects. All LST retrieval methods require validation with field measurements. Nonetheless, the validation of this type of data is a challenge because the LST changes rapidly in time and the measurements must be performed togheter with the sensor overpass. In addition, most methodologies are developed and tested focusing on the Northern Hemisphere. Considering that operational ways of obtaining LST should be constantly investigated, the aim of this paper was to study the effect of the use of temperature-based laboratory measurements in the determination of the emissivity and LST retrieval from orbital remote sensing data. Moreover, it was intended to perform a comparative analysis among the most recent single-channel algorithms available on the literature, applied to band 10 (10.6-11.19 μm) of the Landsat 8 TIRS. The algorithms considered were: Single-channel generalized (SC), Improved Single-channel (ISC) and Improved Mono-window (IMW). A field of coastal dunes was chosen as study area. Two sets of laboratory emissivity measurements were performed with field samples at different temperatures using a Fourier Transform Infrared (FT-IR). Emissivity and temperature data were obtained in the study area concomitantly with the satellite overpass. The Radiative Transfer Equation (RTE) with parameters of global atmospheric profiles was tested as a method of validation. A variation of approximately 2% in the emissivity in relation to the temperature was observed, which could be neglected. The FT-IR presents limitations on the period to acquire stability, however as long as this limitation is respected and the calibration approach correctly carried out, laboratory measurements can achieve optimum accuracy and replace field validation. Available spectral libraries of emissivity have also proved to be a good alternative. All evaluated single-channel methods are suitable for obtaining LST; however, ISC provided superior results in all analyzes, producing higher R² (0.99978) and lower RMSE (0.019) relative to the other algorithms tested

AVALIAÇÃO ESPECTRAL E TEMPORAL DE REMANESCENTES DA MATA ATLÂNTICA COM DADOS SPOT-VGT E VARIÁVEIS METEOROLÓGICAS

A Mata Atlântica é um dos biomas mais ricos do mundo em termos de biodiversidade e endemismo. Nesse sentido, a cidade de Porto Alegre é uma das capitais com maior porcentagem de remanescentes naturais do bioma, o que atesta a necessidade de entendimento e monitoramento da dinâmica dessas áreas florestais. Considerando que as ações de conservação e proteção destas áreas são grandes desafios, este trabalho objetivou analisar a dinâmica espectral e temporal de remanescentes florestais do bioma Mata Atlântica, na cidade de Porto Alegre, RS. Para isto, foram adquiridas séries temporais de Normalized Difference Vegetation Index (NDVI) provenientes de imagens de 10 dias do SPOT Vegetation, no período de 2012-2014. Além dos dados de NDVI, dados meteorológicos de temperatura e precipitação foram utilizados para complementar as análises. Foi observado que o padrão de comportamento da vegetação apresentou um ciclo definido nos dados decendiais de NDVI e este ciclo está claramente associado com as variações nas variáveis climáticas temperatura e precipitação. A variável temperatura mostrou-se mais correlacionada com os dados de NDVI do que a precipitação, principalmente pela capacidade de resiliência dos remanescentes florestais a períodos curtos de déficit hídrico. As variações nos dados temporais de NDVI podem ajudar a compreender o efeito de fatores climáticos sobre a vegetação local, podendo assim auxiliar no planejamento e mitigação de grande escala

MODELING PINUS ELLIOTTII GROWTH WITH MULTITEMPORAL LANDSAT DATA: A STUDY CASE IN SOUTHERN BRAZIL

Remote sensing data are a key proxy to forest monitoring and management at local, regional and global scales. Considering the hypothesis that NDVI and EVI can be used at least during one decade to monitor Pinus elliottii in Southern Brazil, the objective of this study was to identify saturation time after planting of these vegetation indices in a Pinus elliottii plantation and the most suitable index by adjusting theoretical functions to each one of them. Based on Landsat Surface Reflectance Higher-Level Data Products, 32 scenes were selected between 1984 to 2015. A set of theoretical polynomial, gaussian and logistic mathematical functions were applied to fit the experimental data on vegetation indices. The determination coefficient (R²) and RMSE at 95% probability were also used. Finally, EVI efficiency was tested by changing the L parameter. The logistic model was the one that best explained the data resulting from NDVI and EVI over time. NDVI was more effective than EVI for this forest monitoring, identifying the forest growth pattern until its 18 years of age. EVI may have been saturated after 14 years and the L factor may be set to near to zero to achieve a higher coefficient of determination.Remote sensing data are a key proxy to forest monitoring and management at local, regional and global scales. Considering the hypothesis that NDVI and EVI can be used at least during one decade to monitor Pinus elliottii in Southern Brazil, the objective of this study was to identify saturation time after planting of these vegetation indices in a Pinus elliottii plantation and the most suitable index by adjusting theoretical functions to each one of them. Based on Landsat Surface Reflectance Higher-Level Data Products, 32 scenes were selected between 1984 to 2015. A set of theoretical polynomial, gaussian and logistic mathematical functions were applied to fit the experimental data on vegetation indices. The determination coefficient (R²) and RMSE at 95% probability were also used. Finally, EVI efficiency was tested by changing the L parameter. The logistic model was the one that best explained the data resulting from NDVI and EVI over time. NDVI was more effective than EVI for this forest monitoring, identifying the forest growth pattern until its 18 years of age. EVI may have been saturated after 14 years and the L factor may be set to near to zero to achieve a higher coefficient of determination

SPECTRAL REFLECTANCE OF IPÊ-AMARELO LEAVES UNDER DIFFERENT FORMS OF STORAGE AND COLLECTION TIME

The application of spectroradiometry techniques to the study of tree species allows the acquisition of information related to plant physiology and morphology, which can be used in conjunction with orbital images. However, it is known that when a leaf is extracted the senescence process is started, which is characterized by cell constituents degradation, loss of water and modifications of the foliar mesophyll structure. In this context, this study aimed to evaluate the influence of the collection time and storage form on the spectral response of ipê-amarelo leaves. Thus, 32 leaves were collected in distinct times (1h, 2h, 24h and 48h) and conditioned with(C) and without(S) thermal storage. The data were evaluated from the visual analysis of the spectral curves, derivative analysis and statistical analysis. The experiment was conducted in a Randomized block design and data were submitted to analysis of variance (ANOVA) and Tukey test (p = 0.05). Results indicated that thermal storage might delay the senescence process of the leaves. Both the collection time and the storage form affect the pattern of spectral behavior of the leaves of ipê-amarelo. The collection time has not shown significant differences between 1-2h. The largest differences were found between 2-24h after collection

Reflectância espectral de folhas de ipê-amarelo sob diferentes formas de armazenamento e período de coleta

The application of spectroradiometry techniques to the study of tree species allows the acquisition ofinformation related to plant physiology and morphology, which can be used in conjunction with orbital images. However, it is known that when a leaf is extracted the senescence process is started, which is characterized by cell constituents degradation, loss of water and modifications of the foliar mesophyll structure. In this context, this study aimed to evaluate the influence of the collection time and storage form on the spectral response of ipê-amarelo leaves. Thus, 32 leaves were collected in distinct times (1h, 2h, 24h and 48h) and conditioned with(C) and without(S) thermal storage. The data were evaluated from the visual analysis of the spectral curves, derivative analysis and statistical analysis. The experiment was conducted in a Randomized block design and data were submitted to analysis of variance (ANOVA) and Tukey test (p = 0.05). Results indicatedthat thermal storage might delay the senescence process of the leaves. Both the collection timeand the storage form affect the pattern of spectral behavior of the leaves of ipê-amarelo. The collection time has not shown significant differences between 1-2h. The largest differences were found between 2-24h after collection.Reflectância espectral de folhas de ipê-amarelo sob diferentes formas de armazenamento e período de coleta. A aplicação de técnicas de espectrorradiometria para o estudo de espécies vegetais possibilita a obtenção de informações relacionadas a fisiologia e morfologia da planta que podem ser utilizadas em conjunto com imagens orbitais. Contudo, sabe-se que quando uma folha é extraída, o processo de senescência é iniciado, o qual é caracterizado pela degradação dos constituintes celulares, perda de água e modificações da estrutura do mesófilo foliar. Neste contexto, este estudo objetivou avaliar a influência do período de coleta eaforma de armazenamento na resposta espectral de folhas de ipê-amarelo. Assim, 32 folhas da espécie foram coletadas em períodos distintos (1h, 2h, 24h e 48h) e acondicionadas com e sem armazenamento térmico. Os dados foram avaliados a partir da análise visual das curvas espectrais, análise derivativa e estatística. O experimento foi conduzido com delineamento estatístico em blocos aoacaso e os dados submetidos à análise de variância (ANOVA) e teste Tukey (p= 0,05). Os resultados indicam que o armazenamento térmico pode retardar o processo de senescência das folhas. Tanto operíodo de coleta, quanto a forma de armazenamento afetam o padrão de comportamento espectral das folhas de ipê-amarelo. O tempo de coleta não apresentou diferenças significativas entre 1-2h. As maiores diferenças foram encontradas entre 2-24h após a coleta

Eucalyptus forestry in Brazilian Pampa biome: between developmental illusion and sustainable inefficacy

The objective of this article is to analyze how the strategy for the implementation of eucalyptus monoculture in the Brazilian pampa Biome had repercussions on economic, social and environmental aspects. It makes a historical rescue of the formation of the economic development of the region, noting that the forestry project for the region has not escaped the expectations of other strategies imposed on the region in the past, the concentration of wealth of the agrarian elite has never been threatened. Extensive livestock farming, until the beginning of the 20th century, grain monoculture, after World War II, and from the 2000s, forestry, have always been linked to a single logic: the accumulation of capital in the hands of the bourgeoisie. The most aggravating factor in eucalyptus production is the mischaracterization of the Pampa biome, which the richness of this ecosystem, even though it requires better studies, is not taken into account in the policy of forestry expansion. For a legitimate development process is necessary to find endogenous mechanisms to promote development compatible with the improvement of the poorest population and the maintenance of the wealth of the Pampa biome. Factors disregarded in the developmental alternatives proposed for the region to date

CLASSIFICAÇÃO SUPERVISIONADA DE COPAS DE ÁRVORES EM IMAGEM DE ALTA RESOLUÇÃO ESPACIAL

O presente estudo teve como objetivo avaliar o potencial de uso de imagens de alta resolução espacial para a extração da área de copa de árvores em floresta nativa utilizando classificação supervisionada. Uma imagem do sensor multiespectral a bordo do satélite Worldview-2 foi adquirida, na qual foram testados três algoritmos de classificação digital de imagens. Com os resultados das classificações, foram delimitadas 51 copas de árvores, que foram localizadas em campo para a coleta de informações como diâmetro na altura do peito (DAP), altura estimada, diâmetro de base, identificação, e medição de 8 raios de copa para formar a área de copa (AC). O algoritmo SVM apresentou o melhor resultado dentre os métodos de classificação testados. Foi encontrado um R² de 0,57 entre AC em campo e o DAP. A relação AC/DAP indica que houve um aumento da área de copa à medida que aumentou o DAP. O R² entre a AC obtida por satélite e o DAP foi de 0,55. A obtenção do parâmetro AC via classificação supervisionada pode servir de base para delimitação de copas, porém, deve-se ter cuidado com este processo para não superestimar as áreas, devido à complexidade do dossel de uma floresta nativa

COMPARATIVE ANALYSIS OF SPLIT-WINDOW AND SINGLE-CHANNEL ALGORITHMS FOR LAND SURFACE TEMPERATURE RETRIEVAL OF A PSEUDO-INVARIANT TARGET

Land surface temperature (LST) acquired from remote sensing observations is essential to monitor surface energy and water exchange processes at the land-atmosphere interface. Most LST retrieval methodologies are developed focusing on Northern hemisphere. Consequently, Southern hemisphere has a great need for investigating the performance of LST retrieval algorithms already consolidated in the literature. In this paper, we compared a Splitwindow (SW) and a Single-channel (SC) method to retrieve LST from Landsat 8 OLI/TIRS images in a dune field, Southern Brazil. To validate the results, the Atmospheric Correction Parameter Calculator (ACPC) tool and Radiative Transfer Equation (RTE) were used. Results demonstrated that both methodologies are in accordance with the RTE, despite they overestimated the LST. Analysis of variance (ANOVA) indicated that the means are not statistically significant (0.05 level). The correlations between LST retrieved and RTE were strong, producing R² of 0.984 and 0.973 for the SW and SC, respectively, and RMSE values of 1.18 and 1.6. SW also exhibited the best values of MSD (±0.983) and Bias (0.773), thus reinforcing its superior performance. SW can be applied with an accuracy of 1.18 K in Southern Brazil, without needing complex modeling or specific radiosonde

Spatiotemporal influences of LULC changes on land surface temperature in rapid urbanization area by using Landsat-TM and TIRS images

The inverse correlation between NDVI and LST is widely known for its long time series. However, when more specific statistical tests were performed, subtle differences in the correlation behavior over time are more clearly observed. In this work, regression analyses were performed between NDVI and LST at intervals of approximately 10 years, quantifying this relationship for an area of transition from vegetation to urban occupation from 1985 to 2018. The removal of vegetation cover (reduction of 51% to 7% in grassland and 14.4% to 0.6% in forest) to occupy impermeable surfaces ( increase of 31% to 91% in urban areas) caused an average LST increase of 4.18 °C when compared to the first and last decades of the historical series. Temporal analysis allowed us to verify the increase in temperature in the four seasons. The largest difference was 6.36 °C between the first and last decade of autumn, 4.40 °C in spring, 4.09 °C in summer, and 2.41 °C in winter. The results also show that LST has a negative correlation with NDVI, especially in urban areas, with an increase in this correlation during the period (1989: R = −0.55; 1999: R = −0.58; 2008: R = −0.59; 2018: R = −0.76). Our study results will help policymakers understand the dynamics of temperature increases by adding scientifically relevant information on the sustainable organization of the urban environment

ANALYSIS OF THE CLIMATOLOGICAL WATER BALANCE OF THE WATERSHAD ALTO CAMAQUÃ

This work was carried out in the sub-basin called Alto Camaquã, belonging to the Pampa Biome in a region considered stable and of high importance for the conservation of biodiversity. The main economic and socio-cultural activity of the region is family farming, which is also fundamental for the maintenance of the biome due to the coexistence of the field / livestock. In order to understand the behavior of the basin in relation to the months of major deficits and water surpluses, two different methods of spatialization of the results were tested. The main difference between the two methods lies in the determination of CAD. The BHC was calculated for three different rain behaviors: Normal Year; Dry Years; and Rainy Year. The methodologies studied demonstrated great efficiency in the calculation of BHC. The differences that occur in the both methods do not modify the general behavior of the basin and, therefore, do not cause significant differences in what concerns deficits and water excess. However, the second method is more efficient for regions with higher variability of the soil use. The results show that family ranchers suffer from many months of water deficit