Altostratus Clouds: Mid-altitude Gray Layer
Definition: Sheet of featureless, gray clouds in the middle cloud level capable of masking the sun
Description & Characteristics. Altostratus clouds are found in the middle cloud level. And unlike their altocumulus counterpart, they’re often boring to look at. Along with nimbostratus clouds, these clouds don’t have any species associated with them.
But they do come with a handful of cloud varieties, which can help you make the determination if you’re looking at an altostratus cloud or not. If you see a cloud covering the sky’s entirety that’s not very close to the ground, and it’s positioned such that it’s visible through the clouds but giving off a ‘frosted glass’ appearance, chances are good that you’re observing an altostratus translucidus cloud. On the flip side, if the cloud is opaque and you can’t see the sun’s position, then consider it an altostratus opacus.
These clouds can also be responsible for precipitation, though it’s short-lived and not very common. You might also find scud clouds (pannus cloud accessory) underneath the main cloud layer, which can be one more indication that you’re looking at an altostratus cloud.
Altostratus Cloud Facts
Cloud Level (Étage): Middle
Altitude/Height: 2-7km (7,000-23,000 ft)
Latin Term: Derives from alto-, meaning high, and cumulo-, meaning heap
Abbreviation: Altocumulus can be abbreviated as Ac
Cloud Color: Gray to dark gray
Precipitation Potential: Uncommon
Sky Cover: Cloudy to mostly cloudy
Cloud Frequency: Very common
Altostratus Cloud Species
Roses are red, and everyone likes freebies, but altostratus clouds have no associated cloud species. ⛅
Altostratus Cloud Varieties
Altocumulus clouds have five associated cloud varieties: duplicatus, opacus, radiatus, translucidus, and undulatus.
Multilayered
Opaque, masks the sun
Parallel bands and strips
See-through, sun’s position visible
Wavelike, undulating
Altocumulus Cloud Supplementary Features
Altostratus clouds have three supplementary features: mamma, praecipitatio, and virga.
Sac-like, resembling cow udders
Precipitation reaching the surface
Evaporating rain strips
Altostratus Cloud Accessories & Other Clouds
Altostratus clouds have only one associated accessory cloud: pannus.
Ragged frazzles, scud
Similar Cloud Types
While altostratus and altocumulus clouds are found at the same altitude, altostratus clouds are generally a featureless layer, where altocumulus clouds typically have plenty of features. Altostratus clouds don’t have any cloud species associated with them, so if you’re deciding between an altostratus and altocumulus cloud and the cloud you’re observing looks to have an associated cloud species, you should learn towards an altocumulus cloud.
Altostratus vs. Altocumulus
Altostratus and cirrostratus clouds are both layer clouds. A key difference is that if you see an optical phenomena in a cloud and are trying to decide between the two, you’re probably looking at a cirrostratus cloud. Cirrostratus clouds are lighter in color, you can always see the sun’s position through a cirrostratus cloud, which is not always the case with altostratus clouds, which are darker and lower to the ground than cirrostratus clouds.
Altostratus vs. Cirrostratus
Altostratus clouds are generally a featureless layer cloud, whereas stratocumulus clouds have more detail. Remember, if you’re trying to decide between an altostratus and stratocumulus cloud, and the cloud being observed has been determined to have an associated cloud species, it’s not an altostratus cloud.
Altostratus vs. Stratocumulus
Both altostratus clouds and stratus clouds are both layer clouds, so they can certainly look the same. Altostratus clouds are higher in altitude though, which means they won’t touch the ground or mask the tops of tall buildings like a stratus cloud would. When deciding between these clouds, if you’re able to see further off in the distance, chances are likely that you’re looking at an altostratus cloud..