[A-CG46] Biogeochemical linkages between the surface ocean and atmosphere

[ACG46-P03] On the use of a light-weighted membrane drier for CO2 flux measurements in the cold environments

*Taichi Noshiro¹, Daiki Nomura¹, Fumiyoshi Kondo², Keisuke Ono³, Brent Else⁴, Hiroki Ikawa⁵ (1.Hokkaido University, 2.Japan Coast Guard Academy, 3.Institute for Agro-Environmental Sciences, NARO, 4.University of Calgary, 5.Hokkaido Agricultural Research Center, NARO)

Eddy covariance is a useful technique to measure air-ecosystem CO2 exchange. However, its application is difficult in cold environments because of the difficulty to detect small CO2 fluxes. The difficulty for detecting small CO2 flux is partly attributed to the error of the water vapor cross-sensitivity which occurs when CO2 density is measured by an infrared gas analyzer. It may be effective to eliminate vapor in the air sample. However, it is unclear to what extent the air sample needs to be dried such that the effect of the water vapor cross-sensitivity becomes negligible while maintaining accurate high-frequency measurements. Here, we report a pilot study on the CO2 flux measurements using a light membrane drier. The eddy covariance system with a light-weighted membrane drier was employed in a grassland within the property of the Institute for Agro-Environmental Sciences, NARO (Tsukuba, Japan) in the winter 2020. Then the extent of the drying was controlled by regulating the pressure of the counterflows within the membrane drier that was originated from the outlet of the sample air stream. The high-frequency fluctuations of the CO2 density decreased with the extent of the drying increasing. Based on the WPL correction’ formula, however, the error associated with water-vapor cross-sensitivity seems to have a greater impact on the CO2 flux than that of the error associated with the loss of the high-frequency fluctuation of the CO2 density.