Height of base:

Between 600 and 2000 m (2000-6500 ft) (low-level clouds)

Description:

Distinct layer of heaps and rolls,

dark shading in base; bright on top

loose layers, elements are touching

>5º across, larger than the width of 3 fingers across at 30º above horizon

Occurrence:

World-wide; most common cloud genus

Made of:

water droplets

Precipitation:

Mostly none; occasionally light rain or snow reaching ground

Formation:

-          cumulus can join by accumulating under a temperature inversion

-          stratus can develop thermals by preferential temperature increase at bottom versus colder tops

Species:

Stratiformis, lenticularis, castellanus

Varieties:

Opacus, translucidus, perlucidus, undulatus, duplicatus, radiatus, lacunosus

How to distinguish from …

Cumulus (Cu)

Cu do not touch, Sc has flatter top

Altocumulus (Ac)

Cloud elements are smaller than 3 fingers width at 30º above horizon

Higher than 2000 m

Stratus (St)

St indistinct layer with much less variation in tone than Sc layer

Stratocumulus with embedded congestus and

Calvus (see rain core)

Morris, Sep06

Stratocumulus stratiformis perlucidus

(Morris, November 2006)

Stratocumulus stratiformis opacus

(Morris, January 2007)

Stratocumulus,

End of passage of a warm front

Glenwood, Sep 08

Stratocumulus castellanus

Morris, July07