## 3 Results and Discussion
### The Relationship Between Detection Efficiency and Meteorological Factors  
The concentration of aerosol particles is closely related to meteorological phenomena, resulting in varying detection performance of DWL under different weather conditions [30]. Precipitation has the most significant impact on the detection range of DWL, while fog, haze, and dust storms can also influence the detection capabilities. Given that these weather conditions occurred during the experimental period and were characterized by low-visibility phenomena under different humidity conditions, this section focuses on analyzing the detection performance of DWL under varying visibility and humidity conditions. Compared to manually observed visibility at the airport, the meteorological optical range (MOR) offers advantages in objectivity, consistency, and continuity. Therefore, the MOR is used in this study to analyze the relationship between visibility and DWL detection performance. The operational visibility threshold at Gonggar Airport is 5 km, and visibility below 5 km is referred to as low visibility. As shown in Figure 7a, when the MOR exceeds 15 km, the average detection range of the PPI mode stabilizes at approximately 5 km. With a decrease in the MOR, the average detection range of the PPI mode fluctuates slightly but generally increases. When the MOR falls below 6.6 km, the detection range decreases steadily with declining visibility. Under low-visibility conditions (Figure 7b), the average detection range is less than 3 km, and when the MOR drops below 3 km, the average detection range is less than 2 km. These results indicate that the detection range of the DWL remains relatively stable when airport  
Figure 6: Horizontal wind pattern and ground wind speed (black line) for the DBS model on 27 April 2024 **(a)**; vertical wind pattern and temperature (blue line) **(b)**; spectral intensity heatmap **(c)**; and radial wind speed heatmap of the PPI model **(d)**. visibility meets operational standards. However, when visibility approaches or falls below the operational threshold, the detection range of the PPI low-elevation mode decreases significantly with reduced visibility. This provides meteorological personnel with a new perspective for assessing airport visibility. The relationship between visibility and detection performance in DBS mode differs significantly from that in PPI mode. As shown in (Figure 7c), when the MOR exceeds 3.2 km, the average detection range in DBS mode remains stable, fluctuating between 2.2 and 3.1 km. When the MOR falls below 3.2 km, the average detection range decreases linearly with visibility, and when the MOR drops below 3 km (Figure 7d), the average detection range is less than 2 km, showing a similar trend to that of the PPI mode. Due to the severe attenuation effect of large particles on laser pulses, and considering that the attenuation distance in DBS mode occurs at a smaller corresponding MOR value than in PPI mode, it can be inferred that the low visibility at Gonggar Airport may be associated with increased concentrations of large particles in the lower layers of the valley. This leads to severe attenuation of the detection range in PPI mode, while in DBS mode, the laser beam penetrates through the thin high-concentration layer of large particles in the lower atmosphere and quickly reaches the upper layer of smaller particles, allowing a relatively stable detection range when the MOR is slightly below 5 km. However, as the concentration and thickness of large particles in the lower layer increase further, visibility continues to decline, making it difficult for vertical laser pulses to penetrate, causing the detection performance of the DBS mode to deteriorate. The similar decay curves of the PPI and DBS modes when the MOR is below 3 km reflect this trend. For the periods of low visibility that are of particular interest (Figure 8), the detection range of the PPI mode decreases as the MOR decreases. When the MOR is 4-5 km, the median detection range is approximately 3.3 km.