Estudo das radiações solar e terrestre acima e dentro de uma floresta tropical úmida / Solar and terrestrial radiation above and inside a tropical rain forest

AUTOR(ES)
DATA DE PUBLICAÇÃO

2001

RESUMO

In a micrometeorological experiment accomplished during the campaign WETAMC/LBA (from 26/01 to 10/03/1999) measurements of solar and terrestrial radiation were made on a tropical forest environment, at Biological Reservation of Jaru- RO (10° 05 S; 61° 56 W). Data of incident and reflected solar global radiation flux were collected using pyranometers, incident and reflected photosintetically active radiation flux using quantum sensors and the radiation budget using net radiometers, on a micrometeorological tower of 60 meters, in six levels (58, 35, 30, 25, 15 and 2,5 meters). Near the forest ground was installed a set of radiometers composed of twelve pyranometers, twelve quantum sensors and eight net radiometers distributed around the base of the tower. Downward and upward long wave radiation were collected by two pyrgeometers (Kipp & Zonen), just placed on the top of the micrometeorological tower. Additionally, it was collected information of leaf area index (LAI), using a Digital photographic camera, model CID-110, equipped with lens of 8mm. Only 50% of extraterrestrial radiation were observed at the level of forest top, which was spectrally composed by 46% of PAR and 54% of near infrared solar radiation (NIR). Calculated values for albedos of solar radiation (R↓), PAR and NIR were 13,7%, 3,6% e 22,0%, respectively. The relationship between net radiation, Rn, and solar radiation, R↓, was adequatelly described by the expression Rn = 0.825 R↓ - 22,6 Wm-2. Radiation flux near the forest floor were only 3,5%, 1,9% e 2,8% of the forest top radiation flux, respectively, for R↓, Rn e P↓. The spectral composition of the solar radiation reaching the ground was 25% of PAR and 75% of NIR. The extintion profile of radiation inside the canopy could be described by an expression similar to the Beers law. The upper layer of the canopy, between 30 and 35 m, is the more effective in absorbing solar radiation and emmitting long wave radiation. In dominant diffuse radiation conditions the forest can be considered homogeneous for the distribution of its vegetation elements, with a mean Leaf Area Index (LAI) of approximately 5,6 m2/m2.

ASSUNTO(S)

radiação solar solar radiation floresta tropical micrometeorology rain forests micrometeorologia meteorologia reserva biológica de jaru terrestrial radiation radiação terrestre meteorology jaru biological reservation

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