Exploring the link between clouds, radiation, and canopy productivity of tropical savannas

•We explore the influence of clouds on biological productivity of tropical savannas.•Cloudiness increase light use efficiency but decrease canopy productivity of savannas.•Vapour pressure deficit and temperature do not greatly affect light use efficiency.•Decline in radiation of 63% reduce canopy productivity of tropical savannas by 26%. The control of clouds on the canopy gross primary productivity (GPP) was examined at Howard Springs, a tropical savanna site in the Northern Territory, Australia. It was demonstrated in this study that cloudiness can increase the initial canopy quantum efficiency (α), midday light use efficiency (LUE) and water use efficiency (WUE), but decrease GPP in savannas. Thick clouds (clearness index of 0–0.3 in the wet season produced much more diffuse fraction of Photosynthetically Active Radiation (fDPAR>80%), which caused increases in α by 24% and 62% compared to thin clouds (fDPAR between 30% and 80%) and clear sky (fDPAR