Sailor’s Warning

Sailor’s Warning, originally uploaded by Photography by Odille.

“Red sky at night, sailor’s delight.
Red sky in morning, sailor’s warning”

Or substitute shepherd for sailor if you are a landlubber! And is it true?

“Red sky at night, sailors delight.”
When we see a red sky at night, this means that the setting sun is sending its light through a high concentration of dust particles. This usually indicates high pressure and stable air coming in from the west. Basically good weather will follow.

“Red sky in morning, sailor’s warning.”
A red sunrise reflects the dust particles of a system that has just passed from the west. This indicates that a storm system may be moving to the east. If the morning sky is a deep fiery red, it means a high water content in the atmosphere. So, rain is on its way.

And I am always fascinated how the light refraction can make the sun visible before it is over the horizon.

From Wikipedia:
Sunrise is the instant at which the upper edge of the Sun appears above the horizon in the east. Sunrise should not be confused with dawn, which is the (variously defined) point at which the sky begins to lighten, some time before the sun itself appears, ending twilight. Because atmospheric refraction causes the sun to be seen while it is still below the horizon, both sunrise and sunset are, from one point of view, optical illusions.

As sunrise and sunset are calculated from the leading and trailing edges of the sun, and not the centre, the duration of “day” is slightly longer than “night”. Further, because the light from the sun is bent by the atmospheric refraction, the sun is still visible after it is geometrically below the horizon.

Sunrise, 3 September 2010 from Terranora on far north coast NSW, AUstralia. H2 & 50-110 zoom, f5, 1/100, ISO 100 (3-09-10-CF034972)


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