Fog

Lore & Background

Fog forms when water vapor condenses into tiny droplets suspended in the air, often on condensation nuclei such as dust, ice, or salt. It is classified into types based on formation processes: radiation fog forms from cooling of the Earth's surface after sunset; advection fog occurs when moist air passes over a cool surface; and frontal fog forms near weather fronts when raindrops evaporate into cooler air. Sea fog, near saline water, forms as water vapor condenses on bits of salt.

Reader's Guide

Fog is significant for its impact on human activities, including shipping, travel, and warfare, by severely reducing visibility. It also plays a role in atmospheric chemistry and ecology, as fog droplets harbor microbiomes where bacteria actively grow and divide. Research shows that fog water contains bacterial concentrations similar to continental or marine bodies of water, and after fog dissipates, local bacterial concentrations can increase by an average of 45%. Fog types, such as radiation fog and advection fog, are shaped by local topography, wind conditions, and nearby bodies of water, influencing weather patterns and environmental conditions.

Did You Know?

• Fog reduces visibility to less than 1 km (0.62 mi), while mist causes lesser impairment.
• Fog droplets harbor microbiomes where bacteria actively grow, divide, and interact with atmospheric chemistry.
• Sea fog forms as water vapor condenses on bits of salt near saline water.
• After fog dissipates, the concentration of certain bacteria in the local air can increase by an average of 45%.