Development of the Raman lidar technique for remote sensing of spatially resolved surface CO2 VMRs.

Abstract

We, for the first time, developed a Raman lidar system which can remotely detect surface CO2 leakage and measure its volume mixing ratio (VMR). The Raman lidar system consists of the Nd:YAG laser of wavelength 355nm with 80mJ, an optical receiver, and detectors. Indoor CO2 cell measurements show that the accuracy of the Raman lidar is calculated to be 99.89%. Field measurements were carried out over a four-day period in November 2017 at the Eumsong Environmental Impact Evaluation Test Facility (EIT), Korea, where a CO2 leak was located 0.2 km from the Raman lidar. The results show good agreement between CO2 VMR measured by the Raman lidar system (CO2 VMRRaman LIDAR) and that measured by in situ instruments (CO2 VMRIn-situ). The correlation coefficient (R), mean absolute error (MAE), root mean square error (RMSE), and percentage difference between CO2 VMRIn-situ and CO2 VMRRaman LIDAR are 0.81, 0.27%, 0.37%, and 4.92%, respectively. The results indicate that Raman lidar is an effective tool in detecting CO2 leakage and in measuring CO2 VMR remotely. Raman Lidar system was upgraded with a high repetition rate laser and detector which combines analog and photon counting to retrieve the spatial distribution of CO2. Surface CO2 VMRs were retrieved at several distances from the Raman Lidar. The average values of R, MAE, and RMSE between CO2 VMRIn-situ and CO2 VMRRaman LIDAR are 0.92, 2.78 ppm, and 3.26 ppm, respectively. In addition, CO2 emitted from the stack of the resource recovery facility was measured using Raman lidar.