Estudo de características da radiação em uma floresta ombrófila densa, na Amazônia central

Abstract

This study is based on a set of data measured by several sensors installed in the “instant” tower at the ATTO experimental site of the LBA program located in the Uatumã Sustainable Development Reserve - RDSU. This work aimed to study the variability of the components of the Radiation Balance (Br) above a forest canopy with a data period of 36 months (November 2014 to October 2015), in addition to carrying out a case study with 6 months of data (October 2015 to March 2016) of measurements of Photosynthetically Active Radiation (RFA). Among the three years of studies, 2016 presented the lowest volume of rainfall with 1529,79 mm, a reduction of around 15% compared to 2015, which had a total rainfall of 1801,01 mm. The reduction in rainfall volumes is directly associated with the presence of the El Niño episode (EN). To represent the rainy (C) and less rainy (MC) periods, two months of Brazil were chosen, March and August, respectively. The other months can be consulted in the appendix of the work. The highest averages of incident shortwave radiation (ROCin) in the daily cycle occurred between 11 am and 2 pm, with values in the order of 500 to 600 wm-2 in March and 800 to 900 wm-2 in August. The same behavior was observed for the averages of reflected shortwave radiation (ROCref) and for the net radiation (Rn). Terrestrial longwave radiation (ROLter) and atmospheric longwave radiation (ROLatm) showed little variation throughout the year, although ROLatm showed slightly higher values during the rainy season due to greater cloud cover. The integral values of the Br components showed a well-defined seasonality, with higher values during the dry period due to lower cloud cover, and although one period of data corresponds to the 2015/2016 EN, the results found are similar between the three years. The albedo (α) over the years averaged typically for tropical forests, 13%. The RFA variability had its highest averages in the diurnal cycle between 11 am and 12 pm, as well as a slight flattening of the curves at the three levels (10, 28 and 39 meters) at this time. The highest monthly averages were observed between October 2015 and January 2016, while from February to March there was a slight reduction in values, possibly caused by increased cloudiness. A brief analysis of fARFA showed satisfactory results in the use of this variable by the forest canopy, with an average value of around 0,9.