Nadja Gomes Machado

Net radiation estimated by remote sensing in Cerrado areas in the Upper Paraguay River Basin

Abstract The Cerrado is a heterogeneous landscape which is shrinking due to deforestation, giving rise to managed ecosystems. The land cover changes alter net radiation (Rn), which determines the quantity of available energy to the energy balance partition. The objectives of this study were (1) to determine the spatial pattern of the vegetation indices, albedo, and land surface temperature (LST) and (2) to evaluate the Rn estimated by Landsat 5 Thematic Mapper (TM) images over Cerrado areas in the Upper Paraguay River Basin. We estimated the vegetation indices, albedo, LST, and Rn of five selected vegetation types. The values estimated by Landsat 5 TM images had seasonal variations with higher values of the vegetation indices and lower values of the albedo and the LST during the wet season. The riparian and Cerrado strictu sensu had higher values of vegetation indices and lower albedo and LST than grasslands. The Rn estimated by Landsat 5 TM images was highly correlated with the measured Rn. The Rn had a seasonal pattern, following the solar radiation, with higher values during the wet season and varied spatially with higher values in the riparian forest and Cerrado strictu sensu and lower in the grasslands. This study showed the applicability of the Landsat 5 TM images to estimate Rn, which can help to understand the heterogeneity in the study area.

Estimation of gross primary production of the Amazon-Cerrado transitional forest by remote sensing techniques

The gross primary production (GPP) of ecosystems is an important variable in the study of global climate change. Generally, the GPP has been estimated by micrometeorological techniques. However, these techniques have a high cost of implantation and maintenance, making the use of orbital sensor data an option to be evaluated. Thus, the objective of this study was to evaluate the potential of the MODIS (Moderate Resolution Imaging Spectroradiometer) MOD17A2 product and the vegetation photosynthesis model (VPM) to predict the GPP of the Amazon-Cerrado transitional forest. The GPP predicted by MOD17A2 (GPPMODIS) and VPM (GPPVPM) were validated with the GPP estimated by eddy covariance (GPPEC). The GPPMODIS, GPPVPM and GPPEC have similar seasonality, with higher values in the wet season and lower in the dry season. However, the VPM performed was better than the MOD17A2 to estimate the GPP, due to use local climatic data for predict the light use efficiency, while the MOD17A2 use a global circulation model and the lookup table of each vegetation type to estimate the light use efficiency.

Estimation of soil heat flux in a neotropical Wetland region using remote sensing techniques

The direct estimation of the soil heat flux (G) by remote sensing data is not possible. For this, several models have been proposed empirically from the relation of G measures and biophysical parameters of various types of coverage or not vegetated in different places on earth. Thus, the objective of this study was to evaluate the relation between G/Rn ratio and biophysical variables obtained by satellite sensors and evaluate the parameterization of different models to estimate G spatially in three sites with different soil cover types. The net radiation (Rn) and G were measured directly in two pastures at Miranda Farm and Experimental Farm and and Monodominant Forest of Cambara. Rn, G, and G/Rn ratio and MODIS products, such as albedo (α), surface temperature (LST), vegetation index (NDVI) and leaf area index (LAI) varied seasonally at all sites and inter-sites. The sites were different from each other by presenting different relation between measures of Rn, G and G/Rn ratio and biophysical parameters. Among the original models, the model proposed by Bastiaanssen (1995) showed the best performance with r = 0.76, d = 0.95, MAE = 5.70 W m-2 and RMSE = 33.68 W m-2. As the reparameterized models, correlation coefficients had no significant change, but the coefficient Willmott (d) increased and the MAE and RMSE had a small decrease.

EFFECT OF WEATHER CONDITIONS ON THE RISK OF FIRE AND THE NUMBER OF URBAN BURNINGS AND FIRES RECORDED BY REMOTE SENSING IN CUIABÁ-MT, BRAZIL

The establishment of urban fires prevention policies can be defined from studies about its causes. Urban fires are aggravated by specific weather conditions, such as lack of precipitation, high wind speed and low relative humidity, besides it has been related to human activities. The number of fires in the city of Cuiaba MT is high during dry season, which affect the health of the population. Thus, the objective of this study was (i) assess the seasonality of fires attended by the Fire Department and the burnings obtained from satellite imagery; (ii) calculate the Monte Alegre (FMA) and Altered Monte Alegre (FMA+) Formulas; and (iii) correlate fires, burnings, FMA, FMA+, air temperature and rainfall between 2005 and 2009 in Cuiaba/MT. For this, we used the database of the number of occurrences of urban fires attended by the Fire Department Cuiaba MT obtained from Centro Integrado de Operacoes de Seguranca Publica de Mato Grosso (CIOSP) and the number of burnings obtained from Divisao de Geracao de Imagens (DGI) of the Instituto Nacional de Pesquisas Espaciais (INPE) between January 2005 and December 2009. The FMA and FMA+ indices were calculated using the daily precipitation and wind speed and relative humidity measured at 13 o’clock on the Centro Integrado de Defesa Aerea e Controle de Trafego Aereo (CINDACTA I), located in Aeroporto Internacional Marechal Cândido Rondon. The precipitation, air temperature and relative humidity varied annually and seasonally with higher values during the rainy season. The largest number of fires and burnings occurred in the late dry season (August and September), due to low rainfall and relative humidity. The FMA and FMA+ indices were sensitive to weather variations and correlated strongly with the number of fires and burnings without lag, with higher values during the dry season. The FMA and FMA+ indexes can be used to predict future occurrence of fires in Cuiaba-MT.

Spatiotemporal NDVI, LAI, albedo, and surface temperature dynamics in the southwest of the Brazilian Amazon forest

Abstract. During the last decades, the Amazon rainforest underwent uncontrolled exploitation that modified its environmental variables. The current paper analyzes the spatiotemporal dynamics of the normalized difference vegetation index (NDVI), leaf area index (LAI), and surface albedo, and temperature in two different vegetation covers, preserved and deforested areas. We calculated the remote-sensing products using Landsat 5 TM images obtained during the dry season 1984, 1991, 2000, and 2011 of the central region of the State of Rondônia, Brazil. The results showed a reduction of vegetation indexes NDVI (∼0.70 in 1984 to ∼0.27 in 2011) and LAI (∼1.8 in 1984 to ∼0.3 in 2011), with an increase of surface albedo (0.12 in 1984 to 0.20 in 2011) and temperature (∼24°C in 1984 to 30°C in 2011) as the effect of the rainforest converted in grassland during the study period. No changes in any variables were observed in the protected area. Forest conversion into grassland resulted in a decrease of 69% in NDVI and 110% in LAI and a rise of 59% and 24% in albedo and surface temperature, respectively.

CHANGES IN BIOPHYSICAL INDICES DUE TO THE CHANGE OF LAND COVER IN NATIVE CERRADO AREA IN MATO GROSSO STATE

The replacement of natural forests to monoculture can cause changes in local and regional climate due to changes in net radiation and energy exchanges bet...

Estimating of gross primary production in an Amazon-Cerrado transitional forest using MODIS and Landsat imagery

The acceleration of the anthropogenic activity has increased the atmospheric carbon concentration, which causes changes in regional climate. The Gross Primary Production (GPP) is an important variable in the global carbon cycle studies, since it defines the atmospheric carbon extraction rate from terrestrial ecosystems. The objective of this study was to estimate the GPP of the Amazon-Cerrado Transitional Forest by the Vegetation Photosynthesis Model (VPM) using local meteorological data and remote sensing data from MODIS and Landsat 5 TM reflectance from 2005 to 2008. The GPP was estimated using Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) calculated by MODIS and Landsat 5 TM images. The GPP estimates were compared with measurements in a flux tower by eddy covariance. The GPP measured in the tower was consistent with higher values during the wet season and there was a trend to increase from 2005 to 2008. The GPP estimated by VPM showed the same increasing trend observed in measured GPP and had high correlation and Willmotts coefficient and low error metrics in comparison to measured GPP. These results indicated high potential of the Landsat 5 TM images to estimate the GPP of Amazon-Cerrado Transitional Forest by VPM.

Estimated net radiation in an Amazon–Cerrado transition forest by Landsat 5 TM

Abstract. The Amazon–Cerrado transition forest is an extensive region with unique characteristics of radiation exchanges. The measurements of the net radiation (Rn) in this ecosystem are limited to the local scale, and their spatial distribution can be carried out by remote sensing techniques, of which accuracy needs to be evaluated. Thus, the objective of this study was to analyze the accuracy of the model of surface Rn derived from measured solar radiation and estimates of normalized difference vegetation index (NDVI), surface albedo (α), and land surface temperature (LST) estimated by images of Landsat 5 TM in an Amazon–Cerrado transition forest. The Rn, NDVI, α, and LST were estimated by Landsat 5 TM images and related to micrometeorological measurements in a tower of the study area. There was seasonality of micrometeorological variables with higher values of incident solar radiation, air temperature, and vapor pressure deficit during the dry season. However, there was no seasonality of Rn. NDVI decreased and α increased during the dry season, while LST was nearly constant. The Rn had negative correlation with α and positive with NDVI. Both instantaneous and daily Rn estimated with Landsat 5 TM images showed high correlation and low error values when compared with Rn measured in the study area.

Sazonalidade do Balanço de Energia e Evapotranspiração em Área Arbustiva Alagável no Pantanal Mato-Grossense

The Pantanal has flood periods that model the landscape and act as a filter to the establishment and development of plants Anthropogenic or natural disturbances can alter the available energy distribution in the ecosystem. Due to the need of understanding the temporal variability of the energy balance in flood natural landscapes, the objective of this study was to analyze the seasonality of the energy balance in flooded shrub area consisting of Combretum lanceolatum Pohl in Mato Grosso Pantanal. The estimates of latent (LE) and sensible (H) heat flux, and evapotranspiration (ET) were obtained by the method of Bowen ratio between May 2012 and April 2013. The available energy was intended primarily to LE (64.1%), followed by H (35.8%) and almost zero to heat flow in soil (0.1%). The components of the energy balance showed strong seasonality, with highest LE in the wet season and highest H in the dry season. The evapotranspiration was lower during the dry season due to the lower soil water content and transpiration of dominant vegetation in the study area. Results suggest that the study area was limited by the availability of energy and water.

Relations of vegetation and water indices to volumetric soil water content in the Pantanal of Mato Grosso, Brazil

ABSTRACT The measurement of the spatial distribution of volumetric soil water content in the Pantanal is highly difficult, but it can be performed indirectly from vegetation and water indices estimated by remote sensors. Thus, we assessed the relationship between volumetric soil water content (VSWC) and indices of the vegetation and water by TM Landsat 5 images in pasture and forest in the Pantanal of State of Mato Grosso. The VSWC was measured daily by a TDR on a non-flooded pasture in the Fazenda Miranda (FMI) and on a floodplain monodominant area of Vochysia divergens Pohl in the RPPN SESC Pantanal, locally known as Cambarazal (Cam). The VSWC in FMI was significantly correlated with the local rainfall, but it was 5 months delayed with rainfall in Cam. The temporal dynamics of vegetation and water indices were significantly correlated with VSWC. However, some spectral indices were negatively correlated with VSWC in Cam. It suggested different responses to VSWC in each study site. As the vegetation in FMI is water limited, the biomass increased directly with the VSWC during the wet season. The combined effect of the presence of dense woody vegetation and the occurrence of flooding in Cam influenced on the non-positive correlation between VSWC and vegetation and water indices. This article demonstrates the need for further research on the relationship of VSWC and spectra indices in the Pantanal.