As one of the most important components of the atmosphere, ozone is typically categorized into stratospheric and tropospheric ozone. Tropospheric ozone accounts for only 10% of the total ozone content, but its pollution is a significant threat to human health. In 2020, the institute for health metrics and evaluation (IHME) identified environmental ozone as a level 3 risk to human health, linking it to chronic obstructive pulmonary disease (COPD) and premature death. Ozone is not only influenced by its photochemical precursors but also by meteorological factors, pollution transport, and stratospheric ozone. Since the 1970s, differential absorption lidar (DIAL) technology has been widely used for remote sensing of tropospheric ozone concentrations with high spatial and temporal resolution. Early DIAL systems mostly use complex dye lasers, require frequent maintenance, and have poor frequency stability and short lifespans. Nowadays, many ozone lidar systems employ fixed-frequency laser sources such as gas-stimulated Raman lasers. However, the large size and poor thermal conductivity of these devices limit their flexible application in high repetition frequency pumping lasers. To reduce instability caused by tunable light sources and miniaturize the system, an all-solid-state tunable Raman laser is used as the emission source, resulting in a compact ozone DIAL system suitable for multi-platform observation.

This ozone lidar system uses a 532 nm solid-state laser with a high repetition rate as the pump source. It generates a Raman frequency shift using a SrWO₄ Raman crystal, producing a first-order Stokes laser at 560 nm and a second-order Stokes laser at 590 nm. The system then doubles the frequency using a BaB₂O₄ (BBO) crystal. The 590 nm optical path uses a half-wave plate to adjust the polarization, producing a dual violet output at 280 nm and 295 nm. Two high-damage dichroic mirrors are used to separate visible and ultraviolet light. Both ultraviolet beams have a divergence angle of less than 0.35 mrad, as confirmed through testing. As shown in Fig. 1(a), optical components such as the Raman and frequency-doubling crystals are tightly mounted on the optical platform, ensuring the compactness and stability of the optical path. The Cassegrain-type receiving telescope system is compact in both size and structure, with an aperture of about 150 mm, further reducing the overall size of the lidar system. To validate the accuracy of the DIAL’s vertical detection data, validation experiments are carried out.

A thermo fisher model 49i ozone analyzer is installed at a horizontal distance of about 800 m from the lidar, with the lidar mounted on the pylon at an approximate horizontal angle towards the ozone analyzer. The data from both the lidar and the ozone analyzer are processed to calculate the average ozone concentration per hour, excluding data from precipitation and instrument maintenance periods. The inversion results for the lidar’s detection at about 800 m are compared with those of the ozone analyzer. As shown in Fig. 3, the lidar and ozone analyzer data exhibit good consistency over time. The DIAL measurements are about 11 μg/m³ lower than those of the ozone analyzer. This deviation is primarily due to the height difference of about 100 m between the lidar and the ozone analyzer. In clear weather, as solar radiation increases in the morning, ozone generation on the ground is enhanced, and the ozone is transported upward. Before the photochemical reaction diminishes, the ground serves as an ozone source, leading to slightly higher ozone concentration at altitudes up to 100 m. The detection data of the two devices are linearly fitted, and the correlation coefficient reaches 0.888. Then, a sounding balloon is launched at the meteorological bureau of Baoshan District, Shanghai, and its data are compared with those from the lidar at the same location and time. The experiment includes four time nodes: 8:00 AM, 1:00 PM, 6:00 PM, and midnight. Fig. 7 shows the ozone concentration profile from near the ground to an altitude of 3 km as detected by both the lidar and the sounding balloon. The results demonstrate that the mean deviation of ozone concentration within 3 km is less than 7.9 μg/m³, with a correlation coefficient of 0.857. This confirms the reliability of vertical detection of DIAL.

During the Spring Festival period, the ozone concentration is higher than that during non-festival time due to the effects of fireworks and firecrackers. In addition to local photochemical generation, external transport from western regions significantly affects the diurnal variation of ozone. An airborne vehicle lidar experiment conducted in Zhejiang Province shows that high ozone values are concentrated near 600 m. The source of the high ozone concentrations is traced. Throughout the observation period, the ozone lidar system, equipped with a solid Raman light source, operates reliably, providing accurate monitoring data that capture fluctuations in environmental ozone levels and identify ozone concentration hotspots. This system offers a new technical means for the detection of spatial and temporal distribution of regional atmospheric ozone.