Principles and Applications of Multi-Level H₂O/CO₂ Profile Measurement System
2009
Yoo, J.I., Yonsei University, Seoul, Republic of Korea | Lee, D.H., Yonsei University, Seoul, Republic of Korea | Hong, J.K., Yonsei University, Seoul, Republic of Korea | Kim, J., Yonsei University, Seoul, Republic of Korea
The multi-level profile system is designed to measure the vertical profile of H₂O and CO₂ concentrations in the surface layer to estimate the storage effects within the plant canopy. It is suitable for long-term experiments and can be used also in advection studies for estimating the spatial variability and vertical gradients in concentration. It enables the user to calculate vertical fluxes of water vapor, CO₂ and other trace gases using the surface layer similarity theory and to infer their sources or sinks. The profile system described in this report includes the following components: sampling system, calibration and flow control system, closed path infrared gas analyzer (IRGA), vacuum pump and a datalogger. The sampling system draws air from 8 inlets into the IRGA in a sequence, so that for 80 seconds air from all levels is measured. The calibration system, controlled by the datalogger, compensates for any deviations in the calibration of the IRGA by using gas sources with known concentrations. The datalogger switches the corresponding valves, measures the linearized voltages from the IRGA, calculates the concentrations for each monitoring level, performs statistical analysis and stores the final data. All critical components are mounted in an environmental enclosure and can operate with little maintenance over long periods of time. This report, as a practical manual, is designed to provide helpful information for those who are interested in using profile system to measure evapotranspiration and net ecosystem exchanges in complex terrain.
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