Contrails over eastern North Dakota

March 7th, 2011 |
POES AVHRR 10.8 µm "IR window" image

POES AVHRR 10.8 µm "IR window" image

A pair of interesting “Figure 8” aircraft condensation trails (or “contrails”) could be seen on a 1-km resolution POES AVHRR 10.8 µm “IR window” image over eastern North Dakota on 07 March 2011 (above). The contrails appeared slightly colder (brighter white) than the surrounding snow-covered ground surfaces. These contrail patterns were presumably made by military jets conducting training exercises from nearby Grand Forks Air Force Base.

The contrail patterns were even more apparent on the corresponding POES AVHRR 3.7 µm “shortwave IR” image (below). The contrail features appeared darker on the shortwave IR image due to reflection of solar radiation off the small supercooled water droplets that comprised the cloud features — and their shadows appeared as slightly cooler (brighter white) signatures on the surface.

POES AVHRR 3.7 µm "IR window" image

POES AVHRR 3.7 µm "IR window" image

On the 0.63 µm POES AVHRR visible image (below), the contrail shadows showed up very well as darker features against the bright snow-covered ground. Using an Interactive Image Fader Tool, the distance offset between the contrails themselves (darker features on the shortwave IR image) and their shadows (darker features on the visible image) was quite obvious — this distance offset was due to the fairly low sun angle at this time of the day over North Dakota in early March.

POES AVHRR 0.63 µm visible image

POES AVHRR 0.63 µm visible image

Tip of the hat to Gregg Gallina (NOAA/NESDIS/SAB) for bring this interesting feature to our attention!

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