Dry Season Micrometeorology of Central Amazonian Ranchland

This paper presents the first comprehensive micrometeorological measurements to be recorded over post‐deforestation Amazonian ranchland. the ranch was managed for the production of beef cattle and had been created by felling and burning the original rainforest 12 years previously. the measurements allow derivation of the aerodynamic roughness, and a description of the response of the energy balance and surface conductance to the progressing dry season. Zero‐plane displacement and roughness length were derived from wind‐speed profiles as O.17 ± 0.03 m and 0.026 ± 0.003m respectively, while measurement of energy partition was achieved, with excellent agreement, between three independent measurement systems. During the 1990 dry season, average evaporation diminished from 3.8 to 2.1 mm d‐¹ as the Bowen ratio increased from 0.43 to 0.67. Values of surface conductance were derived and these compare well with expected trends.