Measurement of CO2 mixing ratio profiles in the lower and middle troposphere by 1.6 µm DIAL

Abstract:

Vertical profile measurements of CO₂ mixing ratio up to an altitude of 2.5 km have been performed by a 1.6 µm DIAL (Differential absorption lidar) in Tokyo, Japan. The results of these measurements showed that amount of CO₂ mixing ratio increased frequently to 400 and tens of ppm from the ground to an altitude of 2.0 km for nighttime and decreased to around 400 ppm in the boundary layer during fine daytime. On the other hand, such a remarkable diurnal change was rarely seen above an altitude of 2 km.

Therefore, we take on a measurement channel of the "high altitude mode" to our conventional DIAL system in order to measure the CO₂ inflow from urban areas, which is the main cause of the fluctuation of the CO₂ mixing ratio in free air. This system update made it possible to measure CO₂ mixing ratio profiles up to an altitude of 5 km. High altitude mode measurements cover the altitude range of Mt. Fuji Observatory (3776 m) in Japan and Mauna Loa Observatory (3397 m) in Hawaii, United States, which measure CO₂ mixing ratios routinely.

In this presentation, we report the measurement results of CO₂ mixing ratio profiles with the high altitude mode, and discuss the comparison with the measurement results of the CO₂ mixing ratio at Mt. Fuji and Mauna Loa observatories.

Reference

Y. Shibata, C. Nagasawa, and M. Abo, EPJ Web of Conferences. Vol. 237. EDP Sciences, p. 03011, 2020.

Y. Shibata, C. Nagasawa, M. Abo, M. Inoue, I. Morino, and O. Uchino, Sensors, Vol. 18, No. 11, p. 4064, 2018.