Stratus fog is essentially above-ground fog that forms either by lifting morning fog or when cold air moves at low altitudes.
Understanding Stratus Clouds and Fog
The term "stratus" comes from the Latin word strato-, meaning "layer," and describes a cloud formation that appears as a flat, featureless sheet. These clouds, which are often very low to the ground, can produce light drizzle or a small amount of snow. Because of their low altitude, when stratus clouds form at ground level, we experience what we call stratus fog.
How Stratus Fog Forms
Stratus fog can form in two primary ways:
- Lifting of Morning Fog: As the sun heats the earth, morning fog can lift and transform into a low-lying stratus cloud, effectively becoming stratus fog.
- Cold Air Movement: When cold air moves across a low altitude area, it cools the air close to the ground which causes condensation. This results in the formation of stratus clouds at ground level or stratus fog.
Key Characteristics of Stratus Fog
| Characteristic | Description |
|---|---|
| Appearance | Flat, featureless sheet-like cloud close to or touching the ground |
| Precipitation | May produce light drizzle or a small amount of snow |
| Formation | Forms by lifting of morning fog or through cold air moving at low altitudes |
| Altitude | Very low to the ground, generally below 6,500 feet |
Practical Insights
- Stratus fog can significantly reduce visibility, which makes driving hazardous.
- It often appears in the early morning or late at night, especially in calm weather conditions.
- Stratus fog is more common in low-lying areas or valleys where cold air can accumulate.
