In the last two decades, the strong increase of pasturelands over former rainforest areas has raised concerns about the climate change that such change in land cover might cause. In recent years, though, expansion of soybean croplands has been increasingly important in the agricultural growth in Amazonia. In this paper we use the climate model CCM3 to investigate whether the climate change due to soybean expansion in Amazonia would be any different from the one due to pastureland expansion. The land component of the model has been updated with new findings from the Large‐Scale Biosphere Experiment in Amazonia (LBA), and a new soybean micrometeorological experiment in Amazonia. Results show that the decrease in precipitation after a soybean extension is significantly higher when compared to the change after a pastureland extension, a consequence of the very high albedo of the soybean.
Brazilian electric power is mostly based on hydraulics sources through hydropower plant reservoirs that are fed by rivers located in Southeast Brazil. Possible changes in climate can affect the energy supply of the country. The objective of this work is to assess the possible changes in the hydrology of the Upper Grande River Basin (UGRB) under a future climate change scenario, using the Lavras Simulation of Hydrology (LASH) model forced by the outputs of the Eta model, a regional climate model, which was driven by HadCM3 A1B scenario for three time slices in the period between 2011 and 2099. Owing to the surface heterogeneity of the region, the hydrologic model was previously calibrated for four watersheds of the UGRB, which are located in its headwater region and evaluated against observational time series of the present climate period, 1961–1990. In the first future time slice, 2011–2040, the results showed a small reduction in the annual run‐off, but for the other time slices, the trend changed to strong increase in most of the watersheds. The water budget in the region calculated from the Eta model agreed with the run‐off trends, as water excess reduced in the first time slice and gradually increased towards the end of the century. The run‐off components showed intraseasonal variability. The reduction of rains in the end of winter, the dry period in the region, and in the beginning of spring, may cause a change in the dynamics of the groundwater recharge, affecting the base flow, which can extend and intensify the flow recession period, and therefore affect the availability of water resources. On the other hand, the increase of rains during the summer, the rainy season of the region, caused an increase of the direct surface run‐off, which can modify the flood regimes of the rivers in the region.
Relationships between regional climates and oceanic and atmospheric anomalies are important in understanding the rainfall regime of a given region. This work aimed to analyze rainfall erosivity in the Upper Grande River Basin, Southern Minas Gerais State, Brazil; namely the two most representative environments, the Mantiqueira Range (MR) and the Plateau of Campos das Vertentes (PCV). These areas can be affected by the El Niño Southern Oscillation (ENSO) phenomena, which can be evaluated by indicators such as Sea Surface Temperature (SST) for the Niño 3.4 Region. Rainfall erosivity was calculated for individual rainfall events from January, 2006 to December, 2010. Pearson's coefficient of correlation was used to evaluate the relationships between rainfall variables and SST. The coefficients of correlation were significant for both sub-regions. Correlations between the rainfall variables and negative oscillations of SST were also significant, especially in the MR sub-region, however, the Person's coefficients were lower than those obtained for the SST positive oscillations. These results demonstrate that El-Niño phenomenon can be considered an important factor in the intense rainfall behavior of the Upper Grande River Basin.Index terms: Soil erosion, El-Niño, La-Niña, Grande River basin. RESUMORelações entre o clima regional e as anomalias oceânicas e atmosféricas consistem de importantes ferramentas para o entendimento do regime de chuvas intensas em uma dada região. Neste trabalho, objetivou-se analisar a erosividade da chuva na bacia hidrográfica do Alto Rio Grande, sul de Minas Gerais. O estudo considerou as duas sub-regiões mais representativas da mesma, sendo a Serra da Mantiqueira (SM) e o Planalto Campos das Vertentes (PCV). Essas áreas podem ser afetadas pelos fenômenos associados ao El Niño Oscilação Sul (ENSO), o qual pode ser avaliado como função da Temperatura da Superfície do Mar (TSM) para a região do Niño 3.4. A erosividade da chuva foi calculada para cada evento individual de chuva entre janeiro/2006 e dezembro/2010. O coeficiente de correlação de Pearson foi usado para avaliar as possíveis relações entre as variáveis associadas às chuvas erosivas e à TSM. Os coeficientes de correlação foram significativos para ambas as sub-regiões. As correlações entre as variáveis estudadas e as oscilações negativas da TSM também foram significativas, especialmente para a sub-região SM, contudo, os coeficientes foram menores do que aqueles obtidos para oscilações positivas. Os resultados demonstram que o fenômeno El-Niño pode ser mais importante para o comportamento de chuvas intensas na cabeceira da bacia do rio Grande. Termos para indexação:Erosão do solo, El-Niño, La-Niña, bacia do Rio Grande.
This study evaluates the sensitivity of the surface albedo simulated by the Integrated Biosphere Simulator (IBIS) to a set of Amazonian tropical rainforest canopy architectural and optical parameters. The parameters tested in this study are the orientation and reflectance of the leaves of upper and lower canopies in the visible (VIS) and near-infrared (NIR) spectral bands. The results are evaluated against albedo measurements taken above the K34 site at the INPA (Instituto Nacional de Pesquisas da Amazônia) Cuieiras Biological Reserve. The sensitivity analysis indicates a strong response to the upper canopy leaves orientation (χ up ) and to the reflectivity in the near-infrared spectral band (ρ NIR,up ), a smaller sensitivity to the reflectivity in the visible spectral band (ρ VIS,up ) and no sensitivity at all to the lower canopy parameters, which is consistent with the canopy structure. The combination of parameters that minimized the Root Mean Square Error and mean relative error are χ up = 0.86, ρ VIS,up = 0.062 and ρ NIR,up = 0.275. The parameterizations performed resulted in successful simulations of tropical rainforest albedo by IBIS, indicating its potential to simulate the canopy radiative transfer for narrow spectral bands and permitting close comparison with remote sensing products.
Abstract. Relationships between regional climate and oceanic and atmospheric anomalies are important tools in order to promote the development of models for predicting rainfall erosivity, especially in regions with substantial intra-annual variability in the rainfall regime. In this context, this work aimed to analyze the rainfall erosivity in headwaters of Grande River Basin, Southern Minas Gerais State, Brazil. This study considered the two most representative environments, the Mantiqueira Range (MR) and Plateau of Southern Minas Gerais (PSM). These areas are affected by the El Nino Southern Oscillation (ENSO) indicators Sea Surface Temperature (SST) for Niño 3.4 Region and Multivariate ENSO Index (MEI). Rainfall erosivity was calculated for individual rainfall events from January 2006 to December 2010. The analyses were conducted using the monthly data of ENSO indicators and the following rainfall variables: rainfall erosivity (EI30), rainfall depth (P), erosive rainfall depth (E), number of rainfall events (NRE), number of erosive rainfall events (NEE), frequency of occurrence of an early rainfall pattern (EP), occurrence of late rainfall pattern (LP) and occurrence of intermediate rainfall patter (IP). Pearson's coefficient of correlation was used to evaluate the relationships between the rainfall variables and SST and MEI. The coefficients of correlation were significant for SST in the PSM sub-region. Correlations between the rainfall variables and negative oscillations of SST were also significant, especially in the MR sub-region, however, the Person's coefficients were lesser than those obtained for the SST positive oscillations. The correlations between the rainfall variables and MEI were also significant but lesser than the SST correlations. These results demonstrate that SST positive oscillations play a more important role in rainfall erosivity, meaning they were more influenced by El-Niño episodes. Also, these results have shown that the ENSO variables have potential to be useful for rainfall erosivity forecasting in this region.
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