Impact of cruising speed on the ship-based sampling of marine fog frequency

• Main Authors: Yi, Li, Li, King-Fai
• Format: Text
• Language: English
• Published: 2022
• Subjects: Okhotsk; okhotsk sea
• Online Access: https://doi.org/10.5194/acp-2022-593; https://acp.copernicus.org/preprints/acp-2022-593/

Understanding secular changes in marine fog frequency is crucial for marine traffic planning under global change. Voluntary ship-based weather reports from community activities provide unique decadal records of marine weather conditions over world’s oceans, including visibility that implies the presence of marine fog. However, slowly changing external factors (such as the voyage technology, vessel types, etc.) may interfere with the secular changes in ship-based weather reports. Here we identify the cruising speed as an example of “target-induced” sampling biases in ship-based weather reports, where the fog itself causes the bias in its own sampling due to human’s decision. As a demonstration, we rectify the sampling bias in the marine fog frequency by multiplying the ratio of the cruising speeds under fog over the average cruising speeds under all weather conditions. The target-induced sampling biases may cause significant errors in the long-term trends of fog occurrences in the Okhotsk Sea, the Grand Banks, and the North Sea. Similar target-induced sampling biases may also be defined in the ship-based measurements of other weather phenomena.