## 3 Results and Discussion
### The Relationship Between Detection Efficiency and Meteorological Factors
However, when the MOR drops below 1 km, the median detection range decreases significantly to just 0.6 km. In contrast, within the MOR range of 2-5 km, the median detection range of the DBS mode decreases slightly to around 2.4 km. When the MOR is below 1 km, the median detection range of the DBS mode drops significantly, falling to less than 1 km. Overall, the DBS mode performs better than the PPI mode in terms of detection range, except for the 4-5 km range, where the median detection range is slightly lower than that of the PPI mode. For MOR values below 4 km, the detection range of the DBS mode is higher by 0.2 to 0.6 km compared to the PPI mode, indicating that the PPI mode is more sensitive to variations in meteorological factors. It is noteworthy that when the MOR is below 2 km, the detection range distribution for  
Figure 7: The probability distribution of detection ranges for the PPI mode at a 270\({}^{\circ}\) azimuth (**a**,**b**) and the DBS mode (**c**,**d**) as a function of MOR from August 2023 to April 2024. The distributions are presented for two MOR ranges: 0 < MOR < 20 km (**a**,**c**) and 0 < MOR < 5 km (**b**,**d**). The black solid line in the figure represents the average detection range curve. both modes becomes more scattered, which may be related to the impact of different types and sizes of aerosol particles on the backscatter coefficient. Since different types of low-visibility phenomena are closely related to relative humidity, their impact on detection performance also varies [31]. This section focuses on analyzing relative humidity's influence on detection performance under different visibility conditions. As shown in Figure 9a, when relative humidity exceeds 80%, the detection performance of the PPI mode decreases linearly with increasing humidity. This reflects the occurrence of condensation in high-humidity environments [32], where fog, clouds, and even precipitation are the primary causes of laser pulse attenuation. A similar decline is observed in the DBS mode (Figure 9c), indicating that high-humidity conditions significantly affect the detection efficiency of DWL. When relative humidity is below 80%, the detection performance of the PPI mode remains relatively stable, but a noticeable dip occurs at approximately 30% relative humidity. This dip in detection efficiency is particularly evident under low-visibility conditions at around 30% humidity (Figure 9b), where the high-probability detection efficiency zone is more concentrated. Additionally, the frequency of low-visibility events increases at this humidity level, suggesting a favorable environment for accumulating large particles in the lower atmosphere, reducing the detection efficiency of the PPI mode. Figure 8: Box plots of the detection range of the PPI (blue) and DBS modes as a function of MOR in the range of 0 < MOR < 5 km from August 2023 to April 2024. The center, upper, and lower ends of the box plots represent the mean, upper quartile, and lower quartile, respectively. Figure 9: The probability distribution of detection ranges for the PPI mode at a 270\({}^{\circ}\) azimuth (**a**,**b**) and the DBS mode (**c**,**d**) as a function of relative humidity during the period from August 2023 to April 2024. The distributions are presented for two MOR ranges: 0 < MOR < 20 km (**a**,**c**) and 0 < MOR < 5 km (**b**,**d**). The black solid line in the figure represents the average detection range curve. From a frequency perspective, low-visibility phenomena caused by high-humidity environments are relatively rare at Gonggar Airport. When relative humidity is between 40% and 80%, detection performance is slightly improved under low-visibility conditions. This may be related to the increased concentration of small particles in the valley, combined with the hygroscopic growth of aerosol particles [33], which increases the backscattering coefficient and leads to a slight improvement in detection performance.