Guilherme Augusto Verola Mataveli

Improved Albedo Estimates Implemented in the METRIC Model for Modeling Energy Balance Fluxes and Evapotranspiration over Agricultural and Natural Areas in the Brazilian Cerrado

In this study we assessed METRIC (Mapping Evapotranspiration at high Resolution with Internalized Calibration) model performance to estimate energy balance fluxes and evapotranspiration (ET) in two heterogeneous landscapes in the Brazilian Cerrado, including fluxes and ET in both agricultural and natural vegetation. The estimates were evaluated by comparing them to flux tower data collected over sugarcane (USR site), woody savanna (PDG site) and stricto-sensu savanna (RECOR site) areas. The selection of the study years (2005–2007 for USR/PDG sites and 2011–2015 for RECOR site) was based on the availability of meteorological data (to be used as inputs in METRIC) and of flux tower data for energy balance fluxes and ET comparisons. The broadband albedo submodel was adjusted in order to improve Net Radiation estimates. For this adjustment, we applied at-surface solar radiation simulations obtained from the SMARTS2 model under different conditions of land elevation, precipitable water content and solar angles. We also tested the equivalence between the measured crop coefficient (Kc_ec) and the reference evapotranspiration fraction (ETrF or F), seeking to extrapolate from instantaneous to daily values of actual evapotranspiration (ETa). Surface albedo was underestimated by 10% at the USR site (showing a better performance for full crop coverage), by 15% at the PDG site (following the woody savanna dynamics pattern through dry and wet seasons) and was overestimated by 21% at the RECOR site. METRIC was effective in simulating the spatial and temporal variability of energy balance fluxes and ET over agricultural and natural vegetation in the Brazilian Cerrado, with errors within those reported in the literature. Net radiation (Rn) presented consistent results (coefficient of determination (R2) > 0.94) but it was overestimated by 8% and 9% in sugarcane and woody savanna, respectively. METRIC-derived ET estimates showed an agreement with ground data at USR and PDG sites (R2 > 0.88, root mean square error (RMSE) up to 0.87 mm day−1), but at the RECOR site, ET was overestimated by 14% (R2 = 0.96, mean absolute error (MAE) = 0.62 mm.day−1 and RMSE = 0.75 mm day−1). Surface energy balance fluxes and ET were marked by seasonality, with direct dependence on available energy, rainfall distribution, soil moisture and other parameters like albedo and NDVI.

ANÁLISE DO EFEITO DE BACKGROUND NA ESTIMATIVA DA POTÊNCIA E DA ENERGIA RADIATIVA DO FOGO

Atualmente, o sensoriamento remoto orbital e a principal fonte de dados para o estudo das queimadas e para estimar a quantidade de biomassa queimada. Dentre os metodos para estimar a biomassa queimada, o metodo mais efetivo e derivado da Potencia Radiativa do Fogo (FRP) e da Energia Radiativa do Fogo (FRE), sobre a premissa de que a energia emitida como radiacao eletromagnetica durante a combustao e diretamente relacionada com a biomassa queimada. Contudo, devem ser compreendidos os fatores que introduzem erros na FRP e na FRE, como o background, e que prejudicam a acuracia da estimativa da biomassa queimada a partir da FRP e da FRE. O presente trabalho avalia a influencia do background na estimativa da FRP e da FRE a partir de um experimento de combustao em pequena escala, sendo que os resultados encontrados mostram que o mesmo aumentou em media 13% as estimativas obtidas.

Analysis of Precipitation and Evapotranspiration in Atlantic Rainforest Remnants in Southeastern Brazil from Remote Sensing Data

The Atlantic Rainforest has been intensely devastated since the beginning of the colonization of Brazil, mainly due to wood extraction and urban and rural settlement. Although the Atlantic Rainforest has been reduced and fragmented, its remnants are important sources of heat and water vapor to the atmosphere. The present study aimed to characterize and to analyze the temporal dynamics of precipitation and evapotrans‐ piration in the Atlantic Rainforest remnants in São Paulo state, southeastern Brazil, for the period from January 2000 to December 2010. To achieve this, global precipitation and evapotranspiration data from TRMM satellite and MOD16 algorithm as well as forest remnant maps produced by SOS Mata Atlântica Foundation and Brazilian National Institute for Space Research (INPE) were used. Results found in this study demonstrated that the use of remote sensing was an important tool for analyzing hydrological variables in Atlantic Rainforest remnants, which can contribute to better understand the interaction between tropical forests and the atmosphere, and for generating input data necessary for surface models coupled to atmospheric general circulation models.

RELAÇÃO ENTRE O ÂNGULO DE VISADA E A ESTIMATIVA DA POTÊNCIA RADIATIVA DO FOGO

As queimadas atingem grandes areas, constituindo-se como um agente modelador dos ecossistemas e contribuem para o acumulo de gases e aerossois na atmosfera. Atualmente, o sensoriamento remoto e a principal fonte de dados para estudar as queimadas devido a aquisicao de dados globais com uma periodicidade constante. No entanto, sao necessarias mais informacoes sobre as queimadas alem da sua localizacao espacial, dentre elas a biomassa queimada. O metodo mais utilizado para isso atualmente e derivado da Potencia Radiativa do Fogo (FRP), ja que a energia emitida como radiacao eletromagnetica durante a combustao pode ser diretamente relacionada com a biomassa queimada. Contudo, alguns fatores introduzem erros nas estimativas de FRP, como o ângulo de visada. Assim, para avaliar a influencia dessa variavel na FRP foi realizado um experimento de combustao em pequena escala utilizando como biomassa a palha da cana-de-acucar. Ainda, foi determinado o coeficiente de biomassa queimada para a cana-de-acucar. As estimativas obtidas permitiram concluir que a FRP diminui com o aumento do ângulo de visada, e, sendo assim, o ângulo de visada foi considerado no coeficiente de biomassa queimada. Pretende-se futuramente empregar os resultados encontrados para estimar a biomassa queimada e suas emissoes provenientes da queimada pre-colheita da cana-de-acucar.