Techniques for active laser visibility measurement and data inversion

Atmospheric visibility is a fundamental parameter in meteorological monitoring, with significant importance for applications in transportation, industrial and agricultural production, and military operations. Active laser-based visibility measurement represents the most reliable technical approach currently available; however, it remains vulnerable to interference from localized atmospheric anomalies (such as patchy fog and rainfall) or suspended particulate matter (including dust and hard aerosols), which can degrade measurement accuracy and even lead to erroneous results. To address these limitations, this study developed a custom laser-based visibility measurement system and proposes an enhanced retrieval algorithm that incorporates a zonal fitting strategy based on the Klett method. The algorithm operates through three main steps: first, it identifies the optimal linear fitting interval (primary zone) based on the linearity characteristics and coverage range of the detected signal; second, it partitions sub-optimal linear fitting sub-intervals (sub-zones) within the residual region to determine the distal effective detection zone; finally, an adaptive outlier algorithm is applied to retrieve the boundary extinction coefficient based on the distal zone, while the path extinction coefficient is calculated using the Klett method to derive visibility data. The proposed method offers two key advantages: it accurately locates the distal effective detection zone to avoid interference from abrupt disturbances such as patchy fog and rainfall, and it employs an adaptive mechanism to suppress the influence of outliers during boundary extinction coefficient retrieval. Validation through both simulations and experimental data from the self-developed system demonstrates that the algorithm: 1) effectively mitigates retrieval deviations caused by abrupt disturbances including patchy fog, rainfall, and suspended particles; and 2) significantly improves the accuracy and reliability of visibility measurements under atmospheric conditions containing disturbances such as patchy fog, compared to conventional methods.