Everaldo Barreiros de Souza

On the influences of the El Niño, La Niña and Atlantic dipole pattern on the Amazonian rainfall during 1960-1998.

The influence of the large-scale climatic variability dominant modes in the Pacific and in the Atlantic on Amazonian rainfall is investigated. The composite technique of the Amazon precipitation anomalies is used in this work. The basis years for these composites arc those in the period 1960-1998 with occurrences of extremes in the Southern Oscillation (El Nino or La Nina) and the north/south warm (or cold) sea surface temperature (SST) anomalies dipole pattern in the tropical Atlantic. Warm (cold) dipole means positive (negative) anomalies in the tropical North Atlantic and negative (positive) anomalies in the tropical South Atlantic. Austral summer and autumn composites for extremes in the Southern Oscillation (El Nino or La Nina) and independently for north/south dipole pattern (warm or cold) of the SST anomalies in the tropical Atlantic present values (magnitude and sign) consistent with those found in previous works on the relationship between Amazon rainfall variations and the SST anomalies in the tropical Pacific and Atlantic. However, austral summer and autumn composites for the years with simultaneous occurrences of El Nino and warm north/south dipole of the SST anomalies in the tropical Atlantic show negative precipitation anomalies extending eastward over the center-eastern Amazon. This result indicates the important role played by the tropical Atlantic in the Amazon anomalous rainfall distribution.

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).

Four decades of land-cover, land-use and hydroclimatology changes in the Itacaiúnas River watershed, southeastern Amazon

Long-term human-induced impacts have significantly changed the Amazonian landscape. The most dramatic land cover and land use (LCLU) changes began in the early 1970s with the establishment of the Trans-Amazon Highway and large government projects associated with the expansion of agricultural settlement and cattle ranching, which cleared significant tropical forest cover in the areas of new and accelerated human development. Taking the changes in the LCLU over the past four decades as a basis, this study aims to determine the consequences of land cover (forest and savanna) and land use (pasturelands, mining and urban) changes on the hydroclimatology of the Itacaiúnas River watershed area of the located in the southeastern Amazon region. We analyzed a multi-decadal Landsat dataset from 1973, 1984, 1994, 2004 and 2013 and a 40-yr time series of water discharge from the Itacaiúnas River, as well as air temperature and relative humidity data over this drainage area for the same period. We employed standard Landsat image processing techniques in conjunction with a geographic object-based image analysis and multi-resolution classification approach. With the goal of detecting possible long-term trends, non-parametric Mann-Kendall test was applied, based on a Sen slope estimator on a 40-yr annual PREC, TMED and RH time series, considering the spatial average of the entire watershed. In the 1970s, the region was entirely covered by forest (99%) and savanna (∼0.3%). Four decades later, only ∼48% of the tropical forest remains, while pasturelands occupy approximately 50% of the watershed area. Moreover, in protected areas, nearly 97% of the tropical forest remains conserved, while the forest cover of non-protected areas is quite fragmented and, consequently, unevenly distributed, covering an area of only 30%. Based on observational data analysis, there is evidence that the conversion of forest cover to extensive and homogeneous pasturelands was accompanied by systematic modifications to the hydroclimatology cycle of the Itacaiúnas watershed, thus highlighting drier environmental conditions due to a rise in the regions air temperature, a decrease in the relative humidity, and an increase in river discharge.

A Lagrangian identification of the main sources of moisture affecting northeastern Brazil during its pre-rainy and rainy seasons.

This work examines the sources of moisture affecting the semi-arid Brazilian Northeast (NEB) during its pre-rainy and rainy season (JFMAM) through a Lagrangian diagnosis method. The FLEXPART model identifies the humidity contributions to the moisture budget over a region through the continuous computation of changes in the specific humidity along back or forward trajectories up to 10 days period. The numerical experiments were done for the period that spans between 2000 and 2004 and results were aggregated on a monthly basis. Results show that besides a minor local recycling component, the vast majority of moisture reaching NEB area is originated in the south Atlantic basin and that the nearby wet Amazon basin bears almost no impact. Moreover, although the maximum precipitation in the “Poligono das Secas” region (PS) occurs in March and the maximum precipitation associated with air parcels emanating from the South Atlantic towards PS is observed along January to March, the highest moisture contribution from this oceanic region occurs slightly later (April). A dynamical analysis suggests that the maximum precipitation observed in the PS sector does not coincide with the maximum moisture supply probably due to the combined effect of the Walker and Hadley cells in inhibiting the rising motions over the region in the months following April.

Climatologia da estrutura vertical da atmosfera em novembro para Belém-PA

Usando um conjunto de dados para um periodo de 26 anos (1982 a 2007), este trabalho apresentou um estudo diagnostico sobre a estrutura vertical da temperatura do ar, temperatura do ponto de orvalho e umidade relativa sobre a regiao de Belem-PA, durante o mes de novembro. As analises foram conduzidas para duas composicoes contrastantes no que se refere ao regime de precipitacao: a composicao dos anos chuvosos e a composicao dos anos secos, as quais foram estabelecidas objetivamente pelo metodo dos percentis. Os resultados apresentados permitiram concluir que a principal diferenca observada nos perfis de temperatura e umidade atmosferica, comparando-se os perfis dos anos chuvosos e secos, ocorre na camada atmosferica entre os medios e altos niveis da troposfera (entre os niveis padroes de 700 hPa e 400 hPa). Nesta camada, a diferenca entre as temperaturas do ar e do ponto de orvalho e significativamente maior e o contraste de umidade associado a conveccao tambem apresenta os maiores valores. Em geral, as composicoes demonstraram que os perfis de temperatura anomalamente mais quente (frio) e os de umidade anomalamente mais umido (seco) associam-se aos anos com registro de chuva acima (abaixo) do normal na regiao de Belem.

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.

Spatial and Temporal Variability of Rainfall in Eastern Amazon during the Rainy Season

Empirical orthogonal functions (EOF) and composites analysis were employed on pentad data in order to investigate the tropical atmospheric-ocean patterns over the Atlantic Ocean and the spatial-temporal characteristics of the rainfall in eastern Amazon during the peak of the rainy season (February to April). The EOF results evidenced that the Intertropical Convergence Zone (ITCZ) is the main rainfall-producing system in eastern Amazon during the rainy season. Conditions associated with the southward SST gradient in the intertropical Atlantic formed the dynamic patterns that favored the position of the ITCZ to south of the equator, thus explaining the predominance of positive precipitation anomalies in eastern Amazon, especially in the state of Maranhao and northeastern Para during the February and April months.Empirical orthogonal functions (EOF) and composites analysis were employed on pentad data in order to investigate the tropical atmospheric-ocean patterns over the Atlantic Ocean and the spatial-temporal characteristics of the rainfall in eastern Amazon during the peak of the rainy season (February to April). The EOF results evidenced that the Intertropical Convergence Zone (ITCZ) is the main rainfall-producing system in eastern Amazon during the rainy season. Conditions associated with the southward SST gradient in the intertropical Atlantic formed the dynamic patterns that favored the position of the ITCZ to south of the equator, thus explaining the predominance of positive precipitation anomalies in eastern Amazon, especially in the state of Maranhão and northeastern Pará during the February and April months.

Evento extremo de chuva-vazão na bacia hidrográfica do rio Araguari, Amapá, Brasil

O objetivo da investigacao foi analisar vazoes extremas ocorridas entre 9 e 14 de abril de 2011 na bacia do Rio Araguari-AP. A metodologia consistiu de tres etapas principais: 1) re-analise da precipitacao estimada pelo Modelo BRAMS (Brazilian in Development Regional Atmospheric Model System),utilizando como suporte a sinotica do mesmo periodo; 2) analise de vazao nas secoes de monitoramento hidrologico em Porto Platon, Capivara e Serra do Navio (ADCP-Accustic Doppler Profiller Current); 3) analise estatistica da serie historica de vazoes maximas em Porto Platon utilizando distribuicao de Gumbel. Observou-se que o modelo BRAMS capturou parcialmente o padrao do sistema de precipitacao quando comparado com a analise sinotica e com os dados da literatura, mas demandando ainda otimizacao na representacao de respostas hidrologicas extremas. Em Porto Platon foi registrada uma vazao recorde de 4036 m3/s, cujo comportamento foi analisado sob a otica dos mecanismos disponiveis de monitoramento no Estado. Concluiu-se que tais eventos extremos sao pouco detectaveis e oferecem riscos consideraveis aos usuarios da bacia. A previsao de vazao, baseada na serie hidrologica disponivel, era de 100 anos de retorno, mas as analises revelaram que este periodo seria de 360 anos, indicando significativa fragilidade do sistema de previsao de eventos extremos no Estado.

A ocorrência de malária em quatro municípios do estado do Pará, de 1988 a 2005, e sua relação com o desmatamento

O objetivo deste trabalho foi estudar a ocorrencia de malaria em quatro diferentes regioes representativas do estado do Para, buscando suas possiveis relacoes com as taxas de desmatamento. Foi realizado um estudo retrospectivo, com dados secundarios, no periodo de 1988 a 2005, atraves de casos de malaria registrados em quatro municipios do Estado (Anajas, Itaituba, Santana do Araguaia e Viseu), como tambem das taxas de desmatamento fornecidas pelo PRODES-INPE. Aplicou-se a tecnica dos Quantis para se estabelecer cinco categorias ou classes de incidencia da malaria para cada municipio, sendo gerado posteriormente um IPA representativo para o Estado. De 1988 ate 1994, as curvas de incidencia de malaria acompanham os numeros de desmatamento. A partir de 1995, evidenciaram-se anos consecutivos com altos indices de ocorrencia da doenca logo apos os periodos de altas taxas de desmatamento, como registrado nos anos de 1995, 2000 e 2004. Percebeu-se que apos a epoca de intenso desmatamento, os casos de malaria variaram entre alto e muito alto no seu padrao de incidencia, apontando que o desmatamento pode ser um fator de incremento na frequencia e aumento no numero de pessoas infectadas no estado do Para.

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.