Himawari-8 satellite detection of morning terrain fog in a subtropical region

This study explores the construction of a subtropical morning terrain fog detection algorithm for Himawari-8 data. Specifically, the clear sky surface suppression index is constructed to preliminarily remove the clear sky surface by combining Farneback optical flow method. The residual clear sky surface is further removed based on time series brightness temperature difference (BTD) between mid-infrared and thermal infrared. After that, the low-cloud elimination indicator is proposed to remove low clouds and mid-high clouds by coupling the brightness temperatures (BTs) at 10.4 mu m with 12.3 mu m, 13.3 mu m and 8.6 mu m with 9.6 mu m. Finally, the fastmoving low clouds and residual mid-high clouds are removed by using the ratio of adjacent images at the 9.6 mu m BT and the BT at 11.2 mu m. The algorithm validation results show that the probability of detection, the false alarm rate and the critical success index are 0.801, 0.099 and 0.747, which show the acceptable performance. Meanwhile, the algorithm effectively avoids the influence of solar zenith angle. The research is capable of attaining near-real-time fog detection and offers pivotal technical support across diverse domains, including transportation planning, environmental management, human health, and agricultural production.