The Measurement of Atmospheric Fluxes near the Surface: A Generalized Approach

Abstract

A covariance computer capable of accepting analog signals representing any two atmospheric variables is described. The instrument computes the covariance in a frequency band governed at high frequencies by the sensor response times and at low frequencies by capacitive filters. With vertical wind velocity as one input, the instrument has been successfully used for measurement of Reynolds stress, sensible heat flux, and the sum of sensible and latent heats. Given suitable sensors, direct measurement of other fluxes, such as those of CO₂ and water vapor, should be possible. The instrument is small and portable. Power consumption is ∼2 W.