Inversion of lidar signals with the slope method

Area of Science:

• Atmospheric physics
• Remote sensing technology
• Optical remote sensing

Background:

• Lidar (light detection and ranging) systems are crucial for atmospheric profiling.
• The slope method is a common technique for retrieving atmospheric properties from lidar data.
• Understanding the limitations of the slope method is essential for accurate atmospheric measurements.

Purpose of the Study:

• To quantitatively analyze the accuracy of the slope method for determining atmospheric backscatter and extinction coefficients.
• To investigate the influence of white noise and atmospheric extinction on slope method accuracy.
• To assess the impact of these factors on the maximum range of lidar systems.

Main Methods:

• Simulating lidar signals with varying extinction coefficients (10⁻³ to 10 km⁻¹) and signal-to-noise ratios (SNR).
• Applying the slope method, which involves a linear least-squares fit to the logarithm of the range-compensated lidar return.
• Performing quantitative analysis to evaluate the accuracy of retrieved coefficients.

Main Results:

• Backscatter coefficients are accurately determined (<10% error) if extinction < 1 km⁻¹ and SNR > 1000.
• Extinction coefficients are accurately determined (<10% error) only if extinction > 1 km⁻¹ and SNR > 2000.
• Accurate extinction retrieval (<10% error) is not feasible for extinction < 0.1 km⁻¹ without unrealistically high SNR.

Conclusions:

• The slope method is reliable for backscatter retrieval under moderate atmospheric extinction and good SNR.
• Accurate extinction coefficient retrieval using the slope method is challenging, requiring specific conditions of high extinction and very high SNR.
• Lidar system performance and measurement accuracy are significantly constrained by atmospheric conditions and signal quality.