Remote sensing of Arctic marine fog using ship-based ceilometer

Abstract

Arctic marine fog is a severe disastrous weather characterized by drastically reduced visibility, and its occurrence often poses great challenges to navigation and aviation. Accurate measurement of the characteristics of the Arctic marine fog plays a significant role in improving the accuracy of marine fog forecasts in the Arctic region. The Vaisala CL31 ceilometer, with its high sensitivity to liquid water content (LWC), is an effective means of detecting and obtaining the vertical structure of marine fog. In this work, a method to detect fog and retrieve fog thickness based on the ceilometer's backscatter coefficient profile has been proposed. The dataset collected at the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition from September 2019 to September 2020 is analyzed. Results indicate that compared with fog detection results of present weather detector (PWD22), the average deviation of marine fog occurrence probability of the proposed algorithm is within 5 %. Meanwhile, Arctic marine fog has obvious seasonal cycle, with the probability of high-concentration large-particle Arctic marine fog reaching up to 40 % in summer, accompanied by the thickness basically below 300 m. The distribution of marine fog thickness in summer is more concentrated and can last longer, with an average duration of about 6.24 h. In addition, there is an obvious correlation between the marine fog and the atmospheric boundary layer, with the correlation coefficient (CC) between the boundary layer height and the marine fog thickness being 0.7. However, the marine fog is generally shallower than boundary layer height in most cases.