Night heavy fog identification based on FY-4A satellite and its potential analysis in the service of expressway

By analyzing the AGR multi-channel data with high spatial and temporal resolution from the FY-4A satellite and the cases of heavy fog at night in Hubei Province from March 2018 to February 2020, we first determined the identification threshold of night heavy fog at the AGRI long-wave infrared band (10.8 μm) and mid-wave infrared band (3.72 μm), then verified the satellite identification results with the surface meteorological observation data, and finally assessed the potential of night fog identification method in the application of highway service in Hubei Province. The results show that (1) the night heavy fog identified by the FY-4A satellite is basically consistent with that observed by weather stations. (2) The satellite's identification hit rate for heavy fog at night is generally above 70%. Without considering the influence of terrain, the hit rate can be increased by 5% to 8%. Without considering the influence of cloud, the hit rate can be increased by 3% to 4%. (3) Compared with the highway traffic control information of Hubei Province, the hit rate of heavy fog identification from FY-4A satellite at toll stations is higher than 70%. To areas where no heavy fog is observed at some national weather stations but the expressway is closed because of it, the satellite can effectively identify heavy fog. The identification information to heavy fog at night has great application potential in the highway traffic weather services.