Altocumulus

Posted on 2013-08-24 by arjaybe

altocumulus

Photo credit – Simon Eugster

Cloud of the Day – Altocumulus

altocumulus-©-Gi-Gi

We’ve covered the major cloud types of the lower etage, from the surface to 6,500 feet. The cumulus clouds, from fair weather to thunder, and the layer clouds, stratocumulus and stratus, are the most common ones down here. Moving up to the middle etage, above 6,500 feet on up to 20,000 feet, we’ll begin with altocumulus. This cloud is just like stratocumulus, only higher up. If it’s at 6,500 feet it’s stratocumulus, and at 6,600 it’s altocumulus.

Like stratocumulus, altocumulus is an unassuming cloud. It’s only there because there happens to be enough water vapor in the air to condense out into water droplets. As the temperature drops with altitude, it eventually reaches the dew point and clouds form. Altocumulus has a lumpy appearance because of mild convectivity, but it has minimal vertical development. There’s no drama, other than the visual drama that can come with the right lighting. There’s no threat of exciting weather and precipitation is rare. Altocumulus are just clouds.

rjb

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Stratus

Posted on 2013-08-18 by arjaybe

Photo credit - © Francois Paris

Photo credit – © Francois Paris

Cloud of the Day – Stratus

Stratus doesn’t have the identity crisis of stratocumulus. While stratocumulus has features of both layer and cumulus (heap) clouds, but is really neither, stratus is a layer cloud all the way. Forming in calm, moist air, stratus has virtually no definition to it. It is so uniform and featureless that weather observers have difficulty determining the height of its base by eye alone. They have to release a balloon and, knowing its ascent rate, time its disappearance into the cloud. Or they could use an instrument such as lidar.

Photo credit: Nicholas_T / Foter / CC BY

Photo credit: Nicholas_T / Foter / CC BY

Stratus cloud, if it were touching the ground, would be fog. In fact, stratus often forms as a result of a fog lifting.

Precipitation can come from stratus, usually as drizzle or a dusting of snow grains, but it’s only because the air is so moist, rather than because of any real weather activity.

rjb

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Indigo

Posted on 2013-08-12 by arjaybe

Photo credit: 'Ajnagraphy' / Foter / CC BY-ND

Photo credit: ‘Ajnagraphy’ / Foter / CC BY-ND

Prehistory

Photo credit: travfotos / Foter / CC BY-NC

Photo credit: travfotos / Foter / CC BY-NC

People have been using color for a long time. For tens of thousands, probably for over a hundred thousand years, we’ve been using minerals and vegetable extracts to color our clothing and our environments. We were most likely daubing colors on our bodies before that. Cave paintings and rock art made use of it. Ancient textiles show it. Stone age burials have been found containing red ochre, possibly used as a form of blessing for the deceased. For a long time we’ve shown a desire, even a need to embellish nature with color. Sources of dyes and pigments became important factors in all cultures, with various plants and minerals taking on cherished, even sacred auras. Of all the colors, the most esteemed might be blue, due to its rarity and expense.lascaux640x120 Continue reading →

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