A CO2 Profile Retrieving Method Based on Chebyshev Fitting for Ground-Based DIAL

The vertical profile of atmospheric CO
₂
is of great scientific significance in identifying carbon sinks and sources, and estimating CO
₂
emissions or uptakes. Differential absorption Light Detection And Ranging (DIAL), has been widely accepted as the most promising technique to sense atmospheric CO
₂
. The classical method to retrieve measurements, generated from range-resolved detection, is derived from differentiating the measured column content, but its performance in dealing with aerosol backscatter signals is poor. To address this issue, this paper proposes a derivative method, which is based on Chebyshev fitting to the measured differential absorption optical depth. We created a performance evaluation model to assess the performance of the proposed method. Simulations revealed that the error of a single CO
₂
profile in data retrieval can be reduced to less than 4 ppm in 6000 m. The precision of long-term mean CO
₂
profile is expected to be less than 1 ppm. We believe that this novel method can be used in other applications also, e.g., trace gas measurements collected using DIAL, especially when the signal-to-noise-ratio of received signal is small.