X-band opacity of a tropical tree canopy and its relation to intercepted rain, eddy fluxes and other meteorological variables

During summer and autumn 2007, we deployed a 11 GHz microwave radiometer in an experimental tree plantation in Sardinilla, Panama, in the vicinity of the Panama Canal. With this instrument, we determined the opacity of the tree canopy. A collocated eddy-covariance flux tower measured water vapor and carbon dioxide fluxes as well as other meteorological variables such as photosynthetically active radiation (PAR), vapor pressure deficit (VPD) and rain. We observed a pronounced diurnal cycle of the opacity during dry periods and a close relation of the opacity to canopy intercepted rain during rainy periods. The diurnal opacity cycle shows a strong correlation with PAR, VPD and the water vapor flux.