Eddy-Flux Measurements over a Small, Irrigated Area

Abstract

During the summer of 1961, the vertical transfer of water vapor and sensible heat was determined at a height of 4 m over an irrigated field at Davis, Calif. Simultaneous determinations of evaporation at the surface were obtained with a 20-ft weighing Iysimeter, and the corresponding sensible heat transfer computed using an energy balance approach. A comparison of the two methods of determining these vertical fluxes showed excellent agreement early in the summer, but significant differences appeared as the season progressed. These could be attributed to severe contrasts developing between the heavily irrigated site and the surrounding areas, which, with no rain occurring, gradually dried out. The fetch available was of the order 50?190 m depending on wind direction. The results clearly indicated that under the conditions of this experiment, the vertical fluxes were not constant with height, and a condition of horizontal uniformity did not exist.