Navegando por Autor "COSTA, Marcos Heil"

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Acesso aberto (Open Access)
Mecanismos de controle da variação sazonal da transpiração de uma floresta tropical no Nordeste da Amazônia
(Instituto Nacional de Pesquisas da Amazônia, 2005-06) SOUZA FILHO, José Danilo da Costa; RIBEIRO, Aristides; COSTA, Marcos Heil; COHEN, Júlia Clarinda Paiva
In the present work we study the seasonal variation of the transpiration of a tropical forest, and its dependence on biotic and abiótic factors. We used data of the project CARBOPARÁ, part of The Large Scale Biosphere-Atmosphere Experiment in Amazonia (LBA), collected in the National Forest of Caxiuanã, northeastern Amazonia. The average transpiration in a 39-day period during the rainy season was 2.9 mm day-1. In a 29-day period during dry season, the average transpiration was 4.3 mm day-1. The maximum values of the surface conductivity (Cs) are 0.060 m s-1 and 0.045 m s-1 for the rainy and dry period, respectively, observed at 08:00 h local time. The aerodynamic conductance averages (Ca) 0.164 m s-1 and 0.210 m s-1, for the rainy and dry periods, respectively, while the maximum values of Ca are 0.220 and 0.375 m s-1, for the same periods, respectively. It was verified that Cs presents an inverse exponential relationship with the deficit of atmospheric water vapor, for different intervals of global solar irradiance. The hourly analysis of the decoupling factor suggests that the morning transpiration is mainly controlled by the availability of energy. During the afternoon, on the other hand, for both periods studied, the forest becomes progressively coupled to the atmosphere, denoting larger superficial control on the transpiration process.
Acesso aberto (Open Access)
Variação espacial e temporal da precipitação no estado do Pará
(Instituto Nacional de Pesquisas da Amazônia, 2005-06) MORAES, Bergson Cavalcanti de; COSTA, José Maria Nogueira da; COSTA, Antonio Carlos Lôla da; COSTA, Marcos Heil
Studies about the climatology of precipitation in the State of Pará are essential for the planning of agricultural activities. The variation of annual and seasonal precipitation in Pará was analysed based on a historic series of 23 years (1976 1998) of daily rainfall data. The analysis was made for 31 locations in Pará, using geographic information systems techniques, with the results presented in maps. The variability of annual and seasonal precipitation was characterized based on the coefficient of variation and the index of relative interanual variability. The variation of these coefficients for the annual precipitation in Pará was 15 to 30 %. The monthly characteristics of the wet season, in terms of beginning, end and duration, were determined using a criteria proposed by KASSAM (1979). The variation between early planting dates and late planting dates were identified by the periods of julian days of 309 319 and 353 363, respectively.