Diurnal Variations of CO2 Mixing Ratio in the Lower Atmosphere by Three Wavelength DIAL

We have conducted the measurement of high accurate CO₂ mixing ratio profiles by measuring the temperature profiles simultaneously using the three wavelength CO₂ DIAL. The measurements of CO₂ diurnal variation in the lower atmosphere were carried out on sunny and cloudy days respectively. We find out that increasing of the CO₂ mixing ratio occurs over the altitude of about 2 km from the surface during nighttime. On the other hand, the CO₂ mixing ratio decreases over the lower atmosphere during daytime. In particular, the CO₂ mixing ratio decreases earlier on sunny days than on cloudy days after sunrise. This result suggests that CO₂ absorption by photosynthesis greatly contributes to the strength of the solar radiation.