Abstract

The ${{\rm{NO}}_2}$-differential absorption lidar (${{\rm{NO}}_2} {\text -} {\rm{DIAL}}$) technique has been of great interest for atmospheric ${{\rm{NO}}_2}$ profiling. Comprehensive studies on measurement errors in the ${{\rm{NO}}_2} {\text -} {\rm{DIAL}}$ technique are vital for the accurate retrieval of the ${{\rm{NO}}_2}$ concentration. This work investigates the systematic errors of the recently developed continuous-wave (CW) ${{\rm{NO}}_2} {\text -} {\rm{DIAL}}$ technique based on the Scheimpflug principle and a high-power CW multimode laser diode. Systematic errors introduced by various factors, e.g., uncertainty of the ${{\rm{NO}}_2}$ differential absorption cross-section, differential absorption due to other gases, spectral drifting of the ${\lambda _{\rm{on}}}$ and ${\lambda _{\rm{off}}}$ wavelengths, wavelength-dependent extinction and backscattering effect, have been theoretically and experimentally studied for the CW-DIAL technique. By performing real-time spectral monitoring on the emission spectrum of the laser diode, the effect of spectral drifting on the ${{\rm{NO}}_2}$ differential absorption cross-section is negligible. The temperature-dependent ${{\rm{NO}}_2}$ absorption cross-section in the region of 220–294 K can be interpolated by employing a linear fitting method based on high-precision absorption spectra at 220, 240, and 294 K. The relative error for the retrieval of the ${{\rm{NO}}_2}$ concentration is estimated to be less than 0.34% when employing the interpolated spectrum. The primary interference molecule is found to be the glyoxal (CHOCHO), which should be carefully evaluated according to its relative concentration in respect to ${{\rm{NO}}_2}$. The systematic error introduced by the backscattering effect is subjected to the spatial variation of the aerosol load, while the extinction-induced systematic error is primarily determined by the difference between the aerosol extinction coefficients at ${\lambda _{\rm{on}}}$ and ${\lambda _{\rm{off}}}$ wavelengths. A case study has been carried out to demonstrate the evaluation of systematic errors for practical ${{\rm{NO}}_2}$ monitoring. The comprehensive investigation on systematic errors in this work can be of great value for future ${{\rm{NO}}_2}$ monitoring using the DIAL technique.

© 2020 Optical Society of America

Remote sensing of atmospheric NO₂ by employing the continuous-wave differential absorption lidar technique

Liang Mei, Peng Guan, and Zheng Kong
Opt. Express 25(20) A953-A962 (2017)

Broadband continuous-wave differential absorption lidar for atmospheric remote sensing of water vapor

Jiheng Yu, Yuan Cheng, Zheng Kong, Jiaming Song, Yupeng Chang, Kun Liu, Zhenfeng Gong, and Liang Mei
Opt. Express 32(3) 3046-3061 (2024)

Water vapor differential absorption lidar development and evaluation

E. V. Browell, T. D. Wilkerson, and T. J. Mcilrath
Appl. Opt. 18(20) 3474-3483 (1979)

Backscattering measurements of atmospheric aerosols at CO₂ laser wavelengths: implications of aerosol spectral structure on differential-absorption lidar retrievals of molecular species

Avishai Ben-David
Appl. Opt. 38(12) 2616-2624 (1999)

Trace atmospheric SO₂ measurement by multiwavelength curve-fitting and wavelength-optimized dual differential absorption lidar

Takashi Fujii, Tetsuo Fukuchi, Nianwen Cao, Koshichi Nemoto, and Nobuo Takeuchi
Appl. Opt. 41(3) 524-531 (2002)