Evaluation of systematic errors for the continuous-wave NO₂ differential absorption lidar employing a multimode laser...

Area of Science:

• Atmospheric science
• Optical remote sensing
• Spectroscopy

Background:

• Nitrogen dioxide (NO2) is a key atmospheric pollutant and its accurate profiling is crucial.
• Differential Absorption Lidar (DIAL) is a valuable technique for atmospheric measurements.
• Understanding and quantifying measurement errors in NO2-DIAL is essential for reliable data.

Purpose of the Study:

• To investigate systematic errors in the continuous-wave (CW) NO2-DIAL technique.
• To evaluate the impact of various factors on NO2 concentration retrieval accuracy.
• To provide a comprehensive error assessment for practical NO2 monitoring.

Main Methods:

• Theoretical and experimental analysis of systematic errors.
• Real-time spectral monitoring of laser diode emission.
• Linear fitting for temperature-dependent NO2 absorption cross-section interpolation.
• Evaluation of interference from other gases and aerosol effects.

Main Results:

• Spectral drifting effect on NO2 differential absorption cross-section is negligible with real-time monitoring.
• Interpolated NO2 absorption cross-section yields a relative error of <0.34%.
• Glyoxal (CHOCHO) identified as a primary interference molecule; aerosol extinction and backscattering effects also quantified.

Conclusions:

• The CW-NO2-DIAL technique demonstrates high accuracy for NO2 profiling.
• Systematic error evaluation is critical for reliable atmospheric NO2 monitoring.
• This research provides valuable insights for future NO2 DIAL applications.