Edson José Paulino da Rocha

Precipitação sazonal sobre a Amazônia oriental no período chuvoso: observações e simulações regionais com o RegCM3

This paper presents a contribution on the climate modelling studies with emphasis on seasonal rainfall variability in eastern Amazonia, during the austral summer and autumn seasons (DJF and MAM). Based on RegCM3 regional climate simulations for a 26 years period (1982/83 to 2007/08) using high resolution domain scale (30 km) and two different convection schemes (Grell and MIT), it was investigated the model performance to simulate the regional pluviometric distribution in eastern Amazon, with reference to a new observational data base containing regional aspects extracted from a dense rain gauge station network. The quantitative analysis showed that RegCM3 presents systematic errors, especially those related to the dry bias in the Amapa and north/northeast of Para using both schemes Grell and MIT, which indicate that the model does not reproduce ITCZ characteristics over equatorial Atlantic. The simulations using MIT also indicated wet bias in the southwest/south/southeast of Para and north of Tocantins. Moreover, through composites technique, it was also investigated RegCM3 response to reproduce the anomalous spatial rainfall patterns in association with ENSO episodes and interhemispheric SSTa gradient phases across the intertropical Atlantic. The results showed that the model represented realistically well the spatial pattern related to the rainfall anomalies above (below) than normal in most of eastern Amazonia, during the known favourable scenarios, i.e., La Nina and south Atlantic SSTa gradient (unfavourable, i.e., El Nino and north Atlantic SSTa gradient).

Albedo da cultura da soja em área de avanço da fronteira agrícola na Amazônia

O avanco da fronteira agricola na Amazonia pode acarretar graves impactos ambientais, constituindo a mudanca no albedo da superficie um dos principais forcantes. Avaliou-se, neste trabalho, o albedo da soja (Glycine Max (L.) Merryl), plantada em condicoes naturais de campo, na cidade de Paragominas, PA, regiao com grande avanco da fronteira agricola na Amazonia, e se observou relacao direta entre o albedo da soja e o seu indice de area foliar, valor maximo diario variando entre 0,24 e 0,25 associado a um IAF de 7,17 correspondente a 1297,62 graus-dia acumulados. Em termos medios, encontrou-se que a o estadio fenologico mais critico da cultura, tendo como base a mudanca no albedo, e o estadio fenologico de frutificacao na qual a mesma apresenta um albedo medio maximo de 23,3% (± 0,0007). Modelos empiricos foram ajustados para simular a variacao diaria do albedo em funcao do IAF e umidade do solo, ao longo do ciclo, e a variacao diurna do albedo na elevacao solar, para cada estadio fenologico da soja.

Efeitos de um evento de friagem nas condições meteorológicas na Amazônia: um estudo de caso

A influencia do fenomeno da friagem nas variaveis meteorologicas e nos fluxos de energia e CO2 , foi realizada numa area de floresta proxima a regiao de Ji-Parana, Rondonia, durante o mes de junho de 2001. A friagem ocasionou uma diminuicao de 35% no valor da temperatura do ar. Notou-se uma reducao de 75 W.m-2, na radiacao solar incidente, associada a nebulosidade presente em decorrencia da penetracao da massa de ar fria. Consequentemente, tanto o fluxo de calor sensivel (H) quanto o de calor latente (LE), apresentaram uma diminuicao no seu valor medio diario, apresentando uma diferenca em relacao aos dias normais de 8 e 34%, respectivamente. A concentracao de CO2 permaneceu constante, sem apresentar o aumento comum durante a noite, devido a condicao de vento forte tipica da friagem. Em situacao normal o fluxo medio durante o dia de CO2 (-2,44 mmol m-2 s-1) foi menor que durante os dias de friagem (-5,78 mmol m-2 s-1); enquanto que os fluxos medios noturnos foram +1,77mmol m-2 s-1 e +2,83mmol m-2 s-1 durante situacoes de dias normais e de friagem, respectivamente.

Radiation balance in a soybean ecosystem in the Amazon

The continuous advance of the agricultural border in the Amazon has been worrying the scientific community due to the possible environmental impacts caused by this change in land use. The present work evaluated the behavior of the radiation balance components over the soybean crop (Glycine Max (L.) Merryl) in an Amazon area of continuous advance of the agricultural border. The radiation components were continuously monitored during the soybean cycle in 2006 and 2007 in an area of 200 ha. The soybean cultivation in the Amazon presented an abrupt change in t he radiation balance components, with the consequent reduction in the energy available to the environment due to the increase in the surface reflection. There was a significant contribution of the diffuse radiation component in the soybean interception during cloudy conditions, even under incomplete canopy covering. Moreover, after the canopy closure, a similar interaction between soybean and solar radiation occurs, regardless of the cloud condition.

IMPACTS OF SOYABEAN EXPANSION ON THE AMAZON ENERGY BALANCE: A CASE STUDY

SUMMARY A micrometeorological experiment was carried out in an area of soyabean cultivation located in northeastern Para state, Brazil, in order to evaluate impacts on the local energy balance due to replacement of forests by soyabean. The meteorological data from forest ecosystems were collected in Caxiuana forests located in central Para. The energy balance components were obtained using the Bowen ratio technique. Differences in energy balance components between ecosystems were significant during the soyabean growing season and more significant between growing seasons. During the soyabean growing season mean impacts of −15%, −9% and −27% on net radiation, latent heat flux (LE) and sensible heat flux (H), respectively, were observed. At specific soyabean stages, LE was higher than in the forest because of the high soyabean surface conductance of water vapour. However, during the production off-season the impacts were more significant (p < 0.05), showing a reduction of 78% in LE and a substantial increase in H (84%) because of the absence of vegetation cover over this period.

Simulation of soybean growth and yield under northeastern Amazon climatic conditions

The objective of this work was to parameterize, calibrate, and validate a new version of the soybean growth and yield model developed by Sinclair, under natural field conditions in northeastern Amazon. The meteorological data and the values of soybean growth and leaf area were obtained from an agrometeorological experiment carried out in Paragominas, PA, Brazil, from 2006 to 2009. The climatic conditions during the experiment were very distinct, with a slight reduction in rainfall in 2007, due to the El Nino phenomenon. There was a reduction in the leaf area index (LAI) and in biomass production during this year, which was reproduced by the model. The simulation of the LAI had root mean square error (RMSE) of 0.55 to 0.82 m2 m-2, from 2006 to 2009. The simulation of soybean yield for independent data showed a RMSE of 198 kg ha-1, i.e., an overestimation of 3%. The model was calibrated and validated for Amazonian climatic conditions, and can contribute positively to the improvement of the simulations of the impacts of land use change in the Amazon region. The modified version of the Sinclair model is able to adequately simulate leaf area formation, total biomass, and soybean yield, under northeastern Amazon climatic conditions.

Three decades of reference evapotranspiration estimates for a tropical watershed in the eastern Amazon

This study estimated the reference evapotranspiration rate (ETo) for the Itacaiúnas River Watershed (IRW), Eastern Amazonia, and measured the accuracy of eight empirical equations: Penman-Monteith (PM), Priestley-Taylor (PT), Hargreaves and Samani (HS), Camargo (CAM), Thornthwaite (TH), Hamon (HM), Kharrufa (KF) and Turc (TC) using monthly data from 1980 to 2013. In addition, it verifies the regional applicability to the IRW using a for the Marabá-PA station. The methods TC and PM (FAO56) presented the best results, which demonstrate that radiation and higher temperatures are the dominant drivers in the Evapotranspiration process, while relative humidity and wind speed have a much smaller impact. The temporal and spatial variability of ETo for IRW show has strong seasonality, increasing during the dry season and decreasing during the rainy season. The statistical analyses at 1% level of significance, indicates that there is no correlation of the residuals between the dry and rainy seasons, and test of the physical parameters such as mean temperature, solar radiation and relative air humidity explains the variations of ETo.

Modelagem Hidrológica Estocástica Aplicada ao Rio Tocantins para a Cidade de Marabá-PA

Estudos na area da hidrologia mostraram que podemos evitar desastres naturais atraves de previsoes hidrologicas. Nesse trabalho foi utilizada a metodologia de Box-Jenkins de series temporais multivariadas para previsao diaria de nivel fluviometrico do rio Tocantins para o municipio de Maraba-PA, que sofre anualmente com eventos de enchentes, ocasionado pelo aumento periodico do rio Tocantins e pela situacao de vulnerabilidade da populacao que residem em areas de riscos. Foram utilizados dados de niveis diarios observados nas estacoes fluviometricas de Maraba e Carolina e Conceicao do Araguaia da Agencia Nacional de Aguas (ANA), do periodo de 01/12/2008 a 31/03/2011. Evidenciou-se que o modelo ajustado conseguiu capturar a dinâmica das series temporais, com bons prognosticos para o periodo de sete dias, com erro absoluto maximo de 0,08m, e com precisao na previsao acima de 99,00%. Assim, a pesquisa mostrou que o modelo de previsao teve um bom ajuste apresentando bons resultados, podendo ser utilizado como ferramentas de apoio para Defesa Civil, auxiliando no planejamento e preparo de acoes preventivas para o municipio de Maraba.

Classificação climatológica da energia potencial disponível para a convecção na cidade de Belém-PA

A classificacao climatologica da Energia Potencial Disponivel para a Conveccao (CAPE) foi estudada para verificar a possibilidade de ocorrer conveccao e tipo de organizacao em Belem-PA, Brasil, associando-a com eventos extremos de precipitacao (EEPRP). Para a analise da CAPE, utilizou-se dados de radiossondagens do DTCEA e de precipitacao da estacao do INMET, no periodo de 1987 a 2011. Observou-se que a atmosfera local apresenta condicoes favoraveis ao desenvolvimento de conveccao profunda, pois a CAPE com valores maiores que 1000 J/kg foi a mais frequente, representando 61% de todas radiossondagens. O valor de 1000 J/kg, segundo alguns autores, e o limite para conveccao profunda. As classificacoes CAPE 2 e 3 apresentaram tendencias significativas de aumento ao longo dos anos, enquanto a CAPE 1 diminuicao. Essa situacao provavelmente e resultado do aumento da temperatura do ar ocorrido na cidade, impactando o valor da CAPE. Os resultados tambem mostraram que as correlacoes entre a CAPE e EEPRP, a CAPE e os Indices Oceânico do Pacifico e Gradiente Inter-Hemisferico do Atlântico foram baixas. Entao, a CAPE nao e condicao suficiente para formacao de nuvens e precipitacao, pois forcantes dinâmicas de meso e grande escala contribuem decisivamente para modular o clima da cidade.

Impactos do avanço da soja no balanço de radiação no leste da Amazônia

The deforestation of the Amazon, especially for pasture use, has been explored by several researchers who have pointed out as a consequence, serious environmental problems. The continuous expansion of agriculture on areas of cattle ranching in the Amazon, as well as on native areas, must be seen with caution since few studies have been conducted in order to investigate which probable environmental impacts can be generated due to the presence of soybean monoculture in the region. This study evaluates the local impacts of the replacement of forest by soybean (Glycine max (L.) Merrill) on radiation balance components in an area that represents the agricultural border advancement in Amazonia. A micrometeorological experiment was installed in an area of soybean cultivation in Paragominas-PA and data from forest ecosystems were collected in Caxiuana forests located in Melgaco-PA both during 2006 and 2007. During the soybean growing season the mean impact found in net radiation represented a reduction of 17.9% of the value commonly observed in the forest. During the off-season the impact on net radiation was 15.5%. Principal mechanisms that control these impacts were associated with the high soybean albedo and high loss of long wave radiation. Although the greatest impact occurs during the crop growing season, the time of occurrence of this negative effect is restricted to only 1/3 of the year, which leads to a higher impact of the off-season on energy balance in cumulative terms.