Stratus low fog

Stratus low fog is a low cloud that reduces horizontal visibility, common in coastal and humid regions of Brazil, such as the Serra do Mar.

About this subject

Stratus low fog, also known as stratification fog, is a type of low cloud that forms near the Earth's surface, typically below 300 meters in altitude. Unlike other forms of fog, stratus low fog is characterized by a uniform gray layer that extends horizontally, often covering large areas. It forms when warm, moist air comes into contact with a cooler surface, such as the ocean or ground cooled overnight, causing condensation. This phenomenon is especially frequent in coastal regions of Brazil, such as the Serra do Mar, where the combination of oceanic humidity and mountainous terrain favors its occurrence. Stratus low fog has a significant impact on aviation and maritime transport, as it drastically reduces horizontal visibility, often dropping below 1,000 meters. Airports closely monitor this condition with visibility and cloud ceiling instruments, and it can lead to flight delays or cancellations. In daily life, stratus low fog is common on winter mornings in coastal cities like Santos and Rio de Janeiro, forming a white blanket that dissipates as the sun warms the surface. Interestingly, this cloud differs from radiation fog, which forms over inland areas and is shallower. Stratus low fog is also associated with temperature inversions, where a warmer layer of air sits above cooler surface air, trapping pollutants and worsening air quality in large urban centers.

Frequently Asked Questions

How does stratus low fog form?

It forms when warm, moist air passes over a cooler surface, such as the ocean or chilled ground, causing condensation. This is common in coastal areas and during temperature inversions.

What is the difference between stratus low fog and radiation fog?

Stratus low fog is typically thicker and forms in coastal areas, associated with winds and sea moisture. Radiation fog is shallower and occurs inland, after clear, calm nights.

Is stratus low fog dangerous for aviation?

Yes, because it reduces horizontal visibility to less than 1 km, requiring special landing and takeoff procedures, and can lead to flight delays or cancellations.