Disjunct Eddy Covariance Method

Abstract

The eddy covariance method (EC) requires that all frequencies of turbulent motions and trace gas variations contributing to the flux are resolved by the measurement system. In conventional EC systems this is achieved by using anemometers and gas analyzers with fast response time and high data sampling frequency in order to catch the high-frequency end and by using long enough averaging period to catch the low-frequency end. Commonly, instruments with response times of around 0.1 s are used. However, for many atmospheric trace compounds analyzers with this short response time are not readily available or they do not provide continuous time series. One possibility to reduce the requirements for analysers is the disjunct eddy co- variance method (DEC). In DEC only a subset of the full continuous concentration and wind data series is used to obtain the flux. The reduced number of samples allows a noncontinuous (i.e., disjunct) sampling which gives the opportunity of a slower trace gas analysis or of sequential measurement (scanning) of multiple compounds with the same instrument. 10.2