Stratocumulus (Sc)
Sc castellanus
Sc lenticularis
Sc stratiformis virga
Sc opacus praecipitatio
Orographic Sc
Sc undulatus


Stratocumulus undulatus Clouds

These are the clouds which produce a drizzle called "Garua" in South America. In the tropes near Galapagos there are only two seasons known: the cold dry season (June till November) and the warm, humid rain season (January till June) with transition periods up to eight weeks in between. In the dry season the major sea flow is the south equatorial flow, which is directed orthogonally to the South-American coast towards Japan. The major wind in this season is the Southeast trade wind. The sea surface temperature varies between 16 and 28 degC.

In the dry season the cold south equatorial flow meets the warm tropical air. This causes the builtup of an inversion layer at an altitude between 200 and 600 m where the humid air cooled by the sea is located below the warm tropical air. Since there is no vertical exchange, uniform Stratus translucidus, sometimes Stratus opacus clouds are formed at the inversion base above an altitude of 200 m. At the elevations of the islands the vegetation is similar to rainforests which can survive because of this drizzle and fog, whereas at altitudes below 200 m only dry vegetation is found.

The trade winds weaken starting in December and the South equatorial flow will be over-shadowed by the Panama flow coming from the North along the South-American coast. This is a warm flow, which accordingly heats up the air so that the inversion layer disappears and the usual tropical Cumulus clouds with their strong precipitation can form. Now also the plants of the dry zone are able to ingest water.

The image "Hay barn at a wet day" created by Vincent Van Gogh presents a Stratocumulus cloud layer with wave-like structure. Most probably it was painted in 1890 in Saint-Remy. Today it is exhibited in Rijksmuseum Kröller-Möller in Otterloo, The Netherlands.

This cloud layer can be exactly classified as "Stratocumulus stratiformis undulatus opacus", since the sun can not be noticed through the compact cloud cover. The two other ones could be also named as "translucidus".

ScUndulatus6.jpg shows the Stratocumulus cloud cover. The image was taken from an aircraft located above the island Santa Cruz. Here the undulatus-like structure can be better noticed. The Garua clouds dissolved later in the morning, but they could also exist for several days.

This picture shows a view from the Space Shuttle onto the Galapagos region. It is described as followed: "Cloud shrouded volcanoes, Galapagos Islands. This photograph shows how clouds hang at a precise altitude. Volcanic peaks on the Galapagos islands rise above the cloud layer. The circular volcanic summits visible in the picture highlight both the classical conical shape of the volcanic structures and the stability of the cloud altitude. The radiating fan pattern in the cloud around the volcanoes is caused by downslope winds. The equatorial location of the islands contributes to the uniformity of the cloud around the volcano summits. Similar phenomena have been seen on the Martian atmosphere..... " The image clearly shows that the upper limit of the Garua clouds only exist in a single altitude range.

Marsclouds.jpg: Here also an example from the Martian atmosphere. Shown is a cloud cover similar to the one around the top of the "Olympus Mons". This is a shield volcano, which has an altitude of 27 km and is therefore the highest elevation in the solar system. It is often surrounded by layers of thin clouds, which only occur in a certain altitude range.


ScUndulatus1.jpg: S. Borrmann, Volcano Cone on the Island Santa Cruz, Galapagos, September 2000

ScUndulatus2.jpg: S. Borrmann, Island Wolf (Culpepper), Galapagos, September 2000

ScUndulatus3.jpg to ScUndulatus6.jpg: S. Borrmann; near the Island Darwin (Wenman) with view to the North, Galapagos, September 2001

Scspace.jpg: Pat Jones, Shuttle views the Earth: Clouds from Space, 1989.

Marsclouds.jpg: Heuseler, H., R. Jaumann und G. Neukum, The Mars Mission, BLV, 1998; also (Planetary Photo Journal of NASA Jet Propulsion Laboratory) Copyright: NASA

Enigma del Lago: Mural painting in Arcumeggia located near the Lago Maggiore, Northern Italy 19 August 2004, 4:23 p.m.

Vincent van Gogh, "Hay barn at a wet day", Oil painting, 64 cm x 52.5 cm, 1890 (?), Rijksmuseum in Otterloo, Netherlands