During the LBA Wet-to-Dry/AMC and SMOCC field experiments irradiance measurement in the spectral region of photosynthetically active radiation (PAR) was carried out at seven levels inside the canopy at Reserve Jaru, RO. The instruments were mounted on a 60 meter height micrometeorological tower, pointing North, East and West. Sensors pointing up and down were mounted at the top of canopy (39m height) and at 30 m to measure incident and reflected irradiance. At lower levels only sensors pointing up were installed. Aerosol optical properties were determined through measurements performed by a radiometer from AERONET installed at another tower about 800m from the main site. Aerosol optical depth data from a portable sunphotometer from USDA Forest Service and from MODIS aboard Terra and Aqua satellites were also used in this study. Results show that the increase of aerosol loading increases the transmittance of PAR irradiance inside the canopy.