Stratus clouds are a very common cloud formation type. The origin of the name comes from the Latin prefix strato, which means “layer”. These are low-level clouds that take on the appearance of a light storm. They vary in color from dark gray to nearly white.
Characteristics of Stratus Clouds
- Shape: layered
- Latin: stratus – flattened or spread out
- Precipitation: none
- Species: Fractus Nebulosus
- Variety: Opacus Translucidus Undulatus
- Altitude: 0-2,000 m (ca. 6,562 ft)
- Classification: Family C (Low-level)
Stratus clouds can take two forms. The term stratus fractus is used to describe clouds that are ragged and constantly change shape. Stratus nebulosus is a gray, cohesive and fairly homogeneous layer of fog clouds. Stratus clouds have 3 associated cloud varieties:
- and undulatus.
The first variety are thick clouds which do not allow light to pass directly, although light can diffuse through them. Translucidus cloud variety is the opposite of the opacus cloud variety. If you can see the sun through the cloud, then you are looking at a translucidus cloud. Undulatus clouds are wavelike, having a smoothly rising and falling outline. Very dense fog can be classified as stratus nebulosus opacus variety of clouds. It refers to a stratus cloud that has no detail and is dark enough to block sun radiation.
Stratus clouds are low altitude clouds which form up to 800 meters (0.5 miles) above the ground. This type of clouds does not produce halo phenomena except for some occasions at very low temperatures. They appear frequently in the mornings over mountainous areas. Mists and fogs are stratus clouds that form on the ground. The precipitation it produces is of the drizzle type, weak and of short duration. Their temperatures are usually practically the same as those on the earth’s surface.
Shape and Color
This type of clouds appears as a gray haze without a defined shape or structure. They present patches of different degrees of opacity. They vary in color from light to dark gray. During the fall and winter stratus clouds can remain in the sky throughout the day. During the spring and early summer they appear during the early morning and disperse during the day, which indicates good weather.
Formation of Stratus Clouds
Stratus clouds form due to the combined effect of cooling in the lower layers of the atmosphere and turbulence caused by wind. These clouds form close to the Earth’s surface, when a sheet of warm, moist air lifts off the ground and depressurizes. When reaching the ground, they produce fog.
Stratus clouds precipitation potential is very low. At low altitudes they transform into a mist, fog, or drizzle. These clouds are basically mist above level 0. They are formed when cold air moves at low altitudes over an area. Fog is formed by part of the stratus that circulates at ground level. They can also form Stratocumulus clouds.They usually formed in a stable or anticyclonic environment and are more frequent during the winter. Stratus formations are accompanied by precipitation with Nimbostratus clouds. Those high-altitude stratus formations include Altostratus and Cirrostratus clouds.