Measurements of energy fluxes have been taken in a tropical eucalypt forest about 12 m high at 11šS, about 20 km inland on the Tiwi Islands (i.e. Melville and Bathurst Islands) in the Northern Territory of Australia, during November, when a transition to wet monsoon conditions occurs (1). Incoming net radiation Rn was measured at 25 m height on a 30 m tower. Fig 1 shows the average daily variations during 11 days in spring. It can be seen that most of Rn was used in evaporation, which averaged 2.95 mm/d during the period. The dip in Rn at about 10.20 am was due to the buildup of clouds associated with a sea-breeze front. More cumulus clouds occurred later in the day, but they did not grow into cumulonimbi.
Fig 1. Average daily variations of net radiation Rn, heat stored in the ground G, heat imparted to the air from the ground H, and absorbed in evaporation LE, during 13 - 24 November 1995.
(1) Beringer, J. & N. Tapper 1998. The energy balance of a tropical forested site on the Tiwi Islands, Northern Territory, Australia. 23rd Conf. on Agric. and Forest Meteor., Albuquerque, New Mexico (Amer.Meteor. Soc.), preprints p34-7.