Study on Influences of Atmospheric Factors on Vertical CO2 Profile Retrieving From Ground-Based DIAL at 1.6 μm

Differential absorption lidar (DIAL) is widely accepted as the most promising remote sensing means to map the global CO2 concentrations. Nevertheless, diurnal variations and vertical distributions of atmospheric CO2 cannot be obtained by satellite-borne and airborne measurements. Ground-based DIAL systems are developed to fill this gap as well as serve as validations for satellite-borne measurements. Atmospheric factors play significant roles in obtaining accurate range-resolved measurements of CO2.However, the influence of atmospheric factors on the performance of a ground-based DIAL system aiming at CO2 measurements has not been dedicatedly discussed yet. The pressure, temperature and water vapor of the atmosphere have been taken into consideration for performance evaluation after pre-selection of absorption lines around 1.6 μm in this work. Besides, errors caused by variations of aerosols have also been analyzed by using theoretical simulations and real measurements. We found that biases caused by temperature and pressure uncertainties were 0.11~ 0.45 ppm/K and 0.39 ppm/hPa respectively if the central wavelength was utilized as the on-line wavelength. Besides, the water vapor effect could be neglected by cautious selection of on-line and off-line wavelength. At last, if the on-line and off-line wavelengths were transmitted alternatively, the temporal and range resolutions have to be determined very carefully to balance the signal noise ratio of acquired data and tolerable errors derived from variations of aerosols. A variable range resolution is recommended for CO2 measurements at different altitudes to fulfill the target