IEM Daily Feature
Friday, 12 July 2013

Red Sky

Posted: 12 Jul 2013 05:00 AM

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Ames webcam used for sunsets (often facing west) and Nevada webcam used for sunrises (often facing east)
Most are familiar with the old adage; "Red sky at night, sailor's delight. Red sky at morning, sailor take warning." Does this saying apply for us land-locked Iowans? IEM's webcam archive contains an image every five minutes dating back to as far as 2003. For the featured analysis, webcam images approximately 10 minutes prior to sunrise and 10 minutes after sunset were analyzed for amount of red in the sky. The algorithm attempted to differentiate red sky from the red horizon that is common with everyday sun rises and sets. Of 2300 some sunrises and sunsets, 248 red sunrises and 88 red sunsets were identified by an algorithm. For these events, hourly precipitation data from Ames was queried to see if measurable precipitation fell in the 24 hours proceeding the event. The third bar is daily climatology which shows not much of a signal with these events, but there is a slight increase for red sky at morning events. Obviously, a limited sample and computer program does not prove or disprove this adage.

Good = 251
Bad = 28

Tags:   webcam   sun   folklore