Sea Fog
Overview
Sea fog (해무, sea fog) is a fog that occurs over the sea, a meteorological phenomenon where water vapor condenses, reducing visibility to less than 1 km. It typically forms when warm, moist air moves over cold ocean currents and serves as a critical variable in marine weather forecasting and safe ship navigation. Sea fog occurs frequently, especially in the East Sea and the South Sea, and has severe impacts on fisheries and maritime traffic.
Main Content
Formation Principles of Sea Fog
Sea fog is broadly classified into advection fog, evaporation fog, and radiation fog. Advection fog is the most common type, occurring when warm, moist air passes over a cold sea surface, cooling the lower layer and causing water vapor to condense. Evaporation fog forms when cold air passes over a relatively warm sea surface, promoting active evaporation of seawater. Radiation fog forms due to radiative cooling of the sea surface overnight. In waters around Korea, advection fog is predominant, especially frequent in spring and summer.
Classification and Characteristics of Sea Fog
Sea fog is categorized by visibility distance into light sea fog (visibility 500 m to 1 km), moderate sea fog (visibility 200 to 500 m), and dense sea fog (visibility less than 200 m). Sea fog can generally extend horizontally over hundreds of kilometers, while its vertical height is relatively thin, within hundreds of meters. Sea fog tends to thicken in the early morning and morning hours and dissipate during the day due to solar radiation. However, it can persist for several days under the influence of a marine high-pressure system.
Impacts of Sea Fog
Sea fog is one of the greatest threats to ship navigation, causing collision accidents, groundings, and operational halts due to reduced visibility. It also affects aircraft takeoff and landing and increases the risk of traffic accidents on coastal roads. In fishing activities, it reduces operational efficiency and imposes restrictions on marine leisure activities. Particularly along the east coast, large-scale ship accidents caused by sea fog have occurred repeatedly.
Sea Fog Prediction Technology
Sea fog prediction utilizes weather satellites, ocean observation buoys, radar, and numerical models. Recently, sea fog prediction models incorporating artificial intelligence (AI) and deep learning technologies have been developed to improve accuracy. For example, satellite image analysis using convolutional neural networks (CNNs) and time-series prediction using long short-term memory (LSTM) networks are being researched. Additionally, physics-based models that consider critical factors such as sea surface temperature and atmospheric stability for sea fog formation are used in parallel.
Sea Fog and Climate Change
Climate change raises the possibility of changes in the frequency and intensity of sea fog occurrence. Global warming may increase evaporation fog due to rising sea surface temperatures, but changes in atmospheric circulation patterns could reduce advection fog occurrence in some regions. In waters around the Korean Peninsula, the number of sea fog days has shown an increasing trend over the past 30 years, particularly pronounced in the East Sea. This could have long-term impacts on marine ecosystems and maritime safety.
Latest Trends
As of 2024–2025, sea fog research is focused on advancing AI-based prediction models and expanding real-time observation systems. Since 2024, the Korea Meteorological Administration has improved the sea fog advisory system, issuing a 'sea fog warning' for dense sea fog with visibility less than 200 m. Additionally, the Ministry of Oceans and Fisheries is introducing automatic ship identification and collision avoidance systems for sea fog events as part of building a smart maritime traffic system. Internationally, the World Meteorological Organization (WMO) is promoting standardization of sea fog observations and data sharing, and satellite-based sea fog detection technology is advancing. In particular, a sea fog prediction service using data from geostationary ocean observation satellites is scheduled for pilot operation in 2025.
Related Topics
- [[Fog]]
- [[Marine Weather]]
- [[Ship Safety]]