Gas analyzer inter-comparison field experiment for ensuring compatibility of the sensors

Korea Flux Monitoring Network (KoFlux) consists of about a dozen eddy covariance flux tower sites. Based on the carbon/water/energy fluxes between the biosphere and the atmosphere from KoFlux, we have been trying to identify trends and temporal scales of the variability in Korea. A necessary condition for such analyses is that the data from the network are comparable. One of the necessary conditions for the comparability of data is the compatibility of the sensors for measuring fluxes. Model CSAT3 (Campbell Scientific Inc.) of sonic anemometers have been employed almost all the sites of KoFlux, while various gas analyzers have been employed for each site (e.g., Models KH20, EC150, EC155 and IRGASON of Campbell Scientific Inc., Models LI-7500, LI-7500A, LI-7200 and LI-7200RS of LI-COR Inc.). It is well-known that the measured fluxes by the gas analyzers are considerably different, especially in low-flux environments. We had conducted the gas analyzer inter-comparison field experiment from August 2018 to March 2019 at a red pepper field in Yeoju, South Korea (37º 9' 58" N, 127º 40' 2"E) using the four open-path gas analyzers (i.e., Models EC150, IRGASON, LI-7500, LI-7500A) and the three closed-path gas analyzers (i.e., Models EC155, LI-7200, LI-7200RS). The purpose of this experiment is to ensure the compatibility of the gas analyzers in KoFlux. In this presentation, we will present the differences of CO₂ and H₂O fluxes between the sensors and discuss how we can minimize the differences in the post-processing procedure.

Acknowledgment This study was carried out with the support of ´R&D Program for Forest Science Technology (Project No. 2017099A00-1719-BB01)´ provided by Korea Forest Service (Korea Forestry Promotion Institute). We are grateful to Tae Kyung Jung and Ki Woon Kyung of B&P International Co. Ltd., and Sung-Won Choi, Juhan Park and Seung-Won Sohn of National Center for AgroMeteorology, who helped to install the sensors for the field experiment. We specially thank Campbell Scientific Inc. and SOLDAN Inc. for giving us the loan of their instruments during the field experiment.