A Simple Instrument for the Field Measurement of Turbulent Diffusion Flux

Abstract

A new instrument is described which enables integrated values of water and carbon dioxide flux to be obtained under field conditions. The principle of operation is the Thornthwaite-Holzman equation for turbulent diffusion under adiabatic conditions, but a simple adaption would allow automatic correction for nonadiabatic conditions. The instrument is simple and designed for continuous unattended operation under difficult field conditions, where integrated flux values are required over long time intervals. Preliminary tests under such conditions show satisfactory agreement with an independent estimate of evapotranspiration from autumn fields of tall grasses and sedges.