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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Stratocumulus

Posted on 2013-08-09 by arjaybe

Photo credit - Stu Reynolds

Photo credit – Stu Reynolds

Cloud of the Day – Stratocumulus

Stratocumulus is the gravel of the lower etage.* If meteorology were a landscaper, then it would be spreading stratocumulus all over the place. Stratocumulus is a kind of hybrid between the cumulus clouds, defined by vertical development, and stratus clouds, formed in horizontal layers, or strata. Stratocumulus forms in a layer, with minimal vertical development, but it bunches up a bit, giving it a somewhat cumuliform appearance.

stratocumulus-Jim-LeeThe specific heights of the three etages vary with location, being higher closer to the equator and lower closer to the poles. They also vary with the source of the definition. The ambiguity means I will be using the heights that I learned and worked with. Also it’s going to be in feet, rather than meters. The lower etage goes from ground level to 6,500 feet (all heights above ground.) The middle etage from 6,500 to 20,000 feet. And the upper (high) etage is over 20,000 feet. Stratocumulus lives in the lower etage, meaning the height of its base is below 6,500 feet.

If cumulus are the stars of the lower etage, then stratocumulus are the extras. While fair weather cumulus, towering cumulus and cumulonimbus get all the recognition, stratocumulus remains in the obscurity of ubiquity.

Photo credit: Nicholas_T / Foter / CC BY

Photo credit: Nicholas_T / Foter / CC BY

* American National Weather Service definition of etages: “By convention, clouds are vertically divided into three etages (levels); low, middle, and high. Each etage is defined by the range of levels at which each type of clouds typically appears.”

The chance of precipitation from stratocumulus is approximately zero.

rjb

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