08 November 1997 -- Contrails over Wisconsin

08 November 1997 -- Contrails Over Wisconsin

Several jet aircraft condensation trails (contrails) were evident over Wisconsin and northeastern Iowa on 08 November 1997. The GOES-8 visible image above shows an extensive deck of low-level stratus clouds covering most of the region, with several thin contrails (generally oriented NW to SE) located above this stratus deck. Shadows from these contrails can be seen on the tops of the low cloud layer. Image animation shows the southwestward motion of the low cloud features, while the contrails and other high cloud features move to the east.

The orientation of many of the contrails suggests that they were left by aircraft flying to/from Minneapolis, Detroit or Chicago. The GOES-8 infrared (IR) channel 4 image (below left) shows satellite-detected brightness temperatures warmer than -15 C, implying a rather low altitude (below about 15,000 feet). This relatively "warm" contrail temperature results from the thin nature of the contrail cloud -- these features are opaque to "warmer" thermal radiation emitted from the earth and clouds below, so the satellite-sensed contrail temperature is somewhat higher.

The GOES-8 IR channel 2 image (below center) and IR reflectivity product (channel 4 - channel 2, below right) shows colder brightness temperatures and lower reflectivities than the underlying water-droplet-based stratus deck, indicating that the contrails are high altitude ice-crystal-based features.

IR channel 4

IR channel 2

IR reflectivity (4-2)

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