First Application of the Raman Lidar Technique for Remote Sensing of Surface Two Dimensional of CO2 VMRs

We, for the first time, developed a Raman lidar system which can remotely detect CO₂ leakage and measure its volume mixing ratio (VMR). The Raman lidar system consists of the laser, the telescope, an optical receiver, and detectors. Indoor CO₂ cell measurements show that the accuracy of the Raman lidar is calculated to be 99.89%. We also carried out the field measurement using our Raman lidar at an artificial CO₂ leakage site where a CO₂ leakage spot is located 0.2 km away from the Raman lidar instrument for four-day measurement campaign period. The results show good agreement between CO₂ VMRs measured by the Raman lidar system (CO₂ VMR_{Raman LIDAR}) and those measured by in situ instruments (CO₂ VMR_In-situ). The correlation coefficient (R), mean absolute error (MAE), root mean square error (RMSE), and percentage difference between CO₂ VMR_In-situ and CO₂ VMR_Raman LIDAR are 0.81, 0.27%, 0.37%, and 4.92%, respectively. This present study demonstrates a possibility of Raman lidar as an effective tool to detect a CO₂ leakage and measure CO₂ VMR at a distance from the instrument location. We also discuss plan the future for the retrieval of spatially distributed CO₂ VMRs over a large CCS site and natural CO₂ leakage area.