Concentration of Near-surface CO2 over Different Land Covers Measured by Point Observation, Drone Observation and Differential Optical Absorption Spectroscopy

抄録

Near-surface concentrations of atmospheric carbon dioxide (CO2) have been measured intensively for monitoring the concentration trends of the gas species closely related to climate change. Since 2007, the Ibaraki University group has conducted point observations based on Stevenson screens at 11 locations in Ibaraki Prefecture, Japan. Although such a network study can provide valuable observation records, the data are affected by various factors in the surrounding environment, including the topography, distance to wide water bodies, surface coverage, traffic, and other anthropogenic emissions. The method of differential optical absorption spectroscopy (DOAS) is capable of monitoring the CO2 concentration along the optical path of several hundred meters to several kilometers. In this work, we exploit the DOAS approach to obtain regionally averaged data, which are compared with the data from both the fixed-point and drone observations. The total optical path lengths are 160 – 180 m, while the path heights are 1.5 –10 m above ground. As an initial step of the study, two DOAS paths are set up within the university campus where we can readily control the land cover type underneath the measurement path. The results indicate the agreement of trends from the three different observation methods within the range of ±30 ppm, with the influence of vegetation uptake of CO2 during the daytime.