High-range-resolution and long-distance CO₂ profiling using a single-photon differential absorption lidar.

Area of Science:

• Atmospheric Science
• Environmental Monitoring
• Photonics and Optics

Background:

• Lidar technology is crucial for atmospheric CO2 monitoring.
• A fundamental challenge in lidar is balancing long-range detection with high-range resolution.
• Existing methods face limitations in achieving both sensitivity and detailed atmospheric profiling.

Purpose of the Study:

• To develop a lidar system capable of simultaneous long-range detection and high-range resolution for CO2 monitoring.
• To enhance the sensitivity and accuracy of atmospheric CO2 measurements.
• To improve the profile resolution and stability of CO2 concentration retrievals.

Main Methods:

• Integration of a superconducting nanowire single-photon detector (SNSPD) into the lidar system to boost long-range sensitivity.
• Development and application of a novel retrieval algorithm for range-resolved CO2 concentrations from high signal-to-noise ratio (SNR) measurements.
• Field testing over three consecutive nights to validate system performance.

Main Results:

• The enhanced lidar system achieved detection of backscattered signals up to 10 km.
• Demonstrated 30 m range resolution, 5 min temporal resolution, and an effective monitoring range of approximately 8 km.
• The new retrieval algorithm improved range resolution by over an order of magnitude and enhanced retrieval accuracy by 3.8-fold compared to traditional methods.
• Cross-validation with in-situ observations showed a standard deviation of ~10 ppm, confirming high accuracy and robustness.

Conclusions:

• The developed lidar system overcomes the traditional range-resolution tradeoff for CO2 monitoring.
• The novel retrieval algorithm significantly enhances the accuracy and resolution of atmospheric CO2 concentration profiles.
• This technology provides a foundation for advanced CO2 monitoring networks and carbon-cycle research.