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          Institute: MPI für Chemie     Collection: Publikationen MPI für Chemie     Display Documents



ID: 675654.0, MPI für Chemie / Publikationen MPI für Chemie
Effect of imprecise lag time and high-frequency attenuation on surface-atmosphere exchange fluxes determined with the relaxed eddy accumulation method
Authors:Moravek, A.; Trebs, I.; Foken, T.
Language:English
Date of Publication (YYYY-MM-DD):2013-09-16
Title of Journal:Journal of Geophysical Research-Atmospheres
Volume:118
Issue / Number:17
Start Page:10210
End Page:10224
Review Status:Internal review
Audience:Experts Only
Abstract / Description:Relaxed eddy accumulation (REA) systems that employ one single long inlet tube are prone to measurement uncertainties caused by (a) an imprecisely determined lag time between the change of sign in the vertical wind velocity and the switching of the splitter valves and (b) attenuation of high-frequency concentration fluctuations in the tube flow. However, there is currently no commonly applied procedure to address these uncertainties. In this study, we first evaluated the lag time error of the volume flow, mass flow, and cross-correlation method (online and offline) and experimentally determined the magnitude of high-frequency attenuation for a 21.5m long inlet tube of an operating REA system. In a second step, we simulated the impact for different artificial lag time errors and low-pass filter strengths on the REA concentration differences and, thus, on the REA flux, using high-frequency time series of temperature, O-3, CO2, and H2O. The reduction of scalar fluxes was mainly correlated with increasing switching frequencies and ranged for typical lag time errors of the investigated REA system between <5% and 50%, whereas the flux loss due to high-frequency attenuation was between <5% and 30%. The results were very similar for all scalar quantities. Based on our results, we derived empirical correction functions for both imprecise lag times and high-frequency attenuation, discuss their potential application to correct fluxes measured with other REA systems, and give a general procedure to address the uncertainties in future REA setups.
External Publication Status:published
Document Type:Article
Version Comment:Automatic journal name synchronization
Communicated by:N. N.
Affiliations:MPI für Chemie
Identifiers:ISI:000325489300011 [ID No:1]
ISSN:2169-897X [ID No:2]
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