Study on visibility parameterization and its quantitative evaluation along the coast of Beibu Gulf in winter and spring

ZHOU Yue; LÜ Jingjing; GUO Xiaowei; ZHENG Fengqin; WANG Ruili

doi:10.19513/j.cnki.hyqxxb.20250707001

Abstract：The Beibu Gulf is an important hub region for China's new international trade route facing ASEAN,while the significant lack of research on the visibility parameterization in this area has hindered the safety assurance of maritime navigation.By utilizing the observational data on the microphysical characteristics of fog droplets from February to April in 2021 and 2023 across 4 regions of the Beibu Gulf,as well as routine meteorological data from port and island meteorological stations in January,February,March and December from 2016 to 2022,visibility parameterization models based on microphysical factors and meteorological elements are constructed,and their application effects are explored.The results are as follows.(1)The number concentration and liquid water content of fog droplets in the 4 regions of the Beibu Gulf are generally low,with average values of 20-42 particles/cm3 and approximately 0.01 g/m3,respectively.(2)The parameterization model constructed using the number concentration of fog droplets provides the best estimation of visibility in the Beibu Gulf,with correlation coefficients ranging from 0.51 to 0.76.(3)Key meteorological factors,when selected,are effective in distinguishing foggy days from non-foggy days,with relative humidity showing the best discrimination for foggy days across all the 4 regions.Other factors fully consider the thermal and dynamic conditions for the sea fog formation.(4)The visibility assessment model based on BP neural networks shows good consistency across the 4 regions,with correlation coefficients exceeding 0.8 between the estimated and observed visibility values during the training period,and the model in its forecast period successfully captures the peak and valley periods of the visibility evolution.Whether it is a visibility parameterization physical model or statistical model,the application effect is the best when it is constructed regionally for different regions of the Beibu Gulf.