provides monthly and seasonal means of the daily PAR/K↓ ratio. Monthly and seasonal regimes are apparent in the mean daily ratios. The mean daily PAR/K↓ ratio for the hot-dry season was considerably lower than the mean daily ratios for the cool-dry season and the warm-wet season. Cloudless and near-cloudless conditions occurred frequently during the hot-dry season. In more cloudy and humid conditions, the absorption of solar radiation in the infrared portion of the solar spectrum is enhanced, whereas absorption in the PAR waveband does not vary significantly. Thus, an increase in the PAR/K↓ ratio under cloudy skies and a decrease under cloudless skies is found. During the warm-wet season, when cloudy and very cloudy conditions prevailed due to the position of the ITCZ, increases in the mean daily ratio were considerable. The larger standard deviation in the daily PAR/K↓ ratio during the warm-wet season is the result of the greater variability arising from increased humidity and cloudiness. The monthly maximum and minimum daily PAR/K↓ ratios also show a seasonal
trend which generally followed the mean trend. The mean daily PAR/K↓ ratio for the whole experiment period (1.992 mol MJ−1) was probably slightly lower than the actual annual value, as a portion of the warm-wet season was not included in this study. If these data were included, an increase in the mean annual value of the daily PAR/K↓ ratio would be likely