Nitrogen dioxide (NO₂) absorption correction of the sulfur dioxide (SO₂) camera was demonstrated for the first time. The key to improving the measurement accuracy is to combine a differential optical absorption spectroscopy (DOAS) instrument with the SO₂ camera for the real-time NO₂ absorption correction and aerosol scattering correction. This method performs NO₂ absorption correction by the correlation between the NO₂ column density measurement of the DOAS and the NO₂ optical depth of the corresponding channel from the SO₂ camera at a narrow wavelength window around 310 and 310 nm. The error of correction method is estimated through comparison with only using the second channel of the traditional SO₂ camera to correct for aerosol scattering and it can be reduced by 11.3% after NO₂ absorption corrections. We validate the correction method through experiments and demonstrate it to be of greatly improved accuracy. The result shows that the ultraviolet (UV) SO₂ camera system with NO₂ absorption corrections appears to have great application prospects as a technology for visualized real-time monitoring of SO₂ emissions.

The transmission spectrum of a narrow-band interference filter is crucial and highly influenced by factors such as the temperature and angle, thus requiring precise and online measurements. The traditional method of measuring the transmission spectrum of an interference filter involves the use of a spectrometer, but the accuracy of this method is limited. Moreover, placing a narrow-band interference filter inside a spectrometer hinders real-time online measurements. To address this issue, there is demand for high-precision online spectral testing methods. In response to this demand, we propose and experimentally validate a fine spectral characterization method for narrow-band interference filters. This method uses a narrow-linewidth tunable laser, achieving a spectral resolution in the MHz range for online testing. Two types of narrow-band interference filters were tested using the constructed laser spectroscopy experimental system, obtaining a transmission spectrum with a spectral resolution of 318 MHz. In comparison to spectrometer-based methods, our proposed method demonstrates higher spectral accuracy, enables online measurements, and provides more accurate measurements for special spectral interference filters. This approach has significant application value and promising development prospects.

Understanding the thermodynamic horizontal structure of the mesopause is essential for studying atmospheric wave dynamics and energy transport. However, conventional models like MSISE-00 exhibit some discrepancies from lidar observations in the mesopause. To obtain a more reliable horizontal temperature structure, this study integrates coordinated lidar observations from Urumqi, Yuzhong, and Yangbajing with models using a three-dimensional variational (3DVAR) data assimilation method to construct a high-resolution temperature field over northwestern China. The assimilated temperature profiles closely match lidar observations, with the RMSE (root mean square error) of residual reductions of 67.35% at Urumqi, 60.69% at Yuzhong, and 34.80% at Yangbajing. Independent validation at Korla showed a RMSE of residual reductions of 40.14%, confirming the model’s effectiveness. The thermodynamical horizontal structures of the mesopause obtained from this model were also analyzed. The lidar-based model for the mesopause extends the observation results from disparate lidar stations to the area between lidar stations and will contribute to a deeper understanding of upper atmospheric dynamics.

The 589 nm three-frequency lidar systems are widely employed for detecting atmospheric parameters in the mesosphere and lower thermosphere (MLT). Recently, the single-peak atomic frequency discriminator (SPAFD) has enabled 589 nm three-frequency lidars to measure wind fields in the stratosphere and mesosphere. However, research on their application for near-surface aerosol measurements remains limited. This paper proposes a method for diurnal aerosol detection using the 589 nm three-frequency lidar integrated with SPAFD. The specific configuration of the lidar system is described in detail, along with the retrieval algorithm for aerosol optical parameters derived from the three-frequency backscatter signals. Continuous 69-h observation results of the aerosol backscatter ratio are provided, followed by an analysis of the diurnal evolution of the planetary boundary layer (PBL) height. This approach enables existing 589 nm lidar systems to acquire aerosol diurnal detection capabilities without additional hardware costs or operational expenses. At present, the retrieval of aerosol extinction coefficients is constrained to altitudes above 10 km due to geometric overlap factor limitations. To overcome this, a dedicated low-altitude detection channel will be integrated in future iterations to enable full-altitude measurements. This advancement will establish the 589 nm lidar as a highly efficient tool for full-altitude, diurnal atmospheric detection.