'Experiences Using the Newer EC155 Closed-Path Infrared CO2/H2O Analyzer for Measuring Eddy Covariance in Agricultural and Natural Ecosystems'

Improved fast-response closed-path infrared CO2/H2O analyzers designed for use with eddy covariance (EC) systems in remote locations promise improved performance in comparison to traditional closed-path systems. Here we present a short-term study that was undertaken to assess the performance, robustness and ease of operation of the newer-class EC155 (Campbell Scientific, Logan UTAH) operating independently in a soybean field and side-by-side with a LI-7000 (LI-COR, Lincoln, NE) in both a corn field and a wetland bog in Ontario, Canada. The LI-COR Li-7000 was used as a baseline for the study as it is a well-established, reliable traditional closed-path infrared CO2/H2O analyzer that has been successfully used in long term studies at both sites. The EC155 is part of the CPEC200--a complete eddy covariance system that also features a CSAT3A sonic anemometer and a CR3000 data logger with a cellular modem. The data-logger program controls automatic self-calibrations and computes on-line flux measurements at the study site. The EC measuring systems equipped with the LI-7000 infrared gas analyzer have a two different styles of Gill anemometers; a HS 3-axis in the corn study and a R3 3-axis in the bog study (Gill Instruments, Lymington, Hampshire, UK). The three study sites were relatively flat and homogeneous. Flux data was acquired during the peak growing season in the soybean and corn fields and for approximately 5 weeks during cooler late autumn weather at the bog site. The CPEC200 was within 20 m of the permanent LI-7000 flux system in the corn field and on the same tower in the wetland bog site. We present results focused on the general operations of the CPEC200, performance of the two systems during various meteorological conditions, and spectral response. Additionally, we show comparative results between flux results calculated by the CPEC200 on-board data logger and post-study flux calculations. During operations, the EC155/CPEC200 proved to be reliable with minimal downtime, no calibration needs and low maintenance requirements. Data processed to date illustrates the positive capabilities of the newer class system.