Going in circles
The writer discusses his attempts to discover the origin of an atmospheric slinky over the North Sea.
The slinky, caught on an infrared image from the NOAA-14 satellite, was more than likely caused by the condensation trail left by a jet aircraft. As air at cruising altitude flows into a jet engine, it is heated and made humid by water vapor.
Once discharged from the engine, the now heated and moistened air merges with surrounding air, and, depending on the temperature and humidity of each of the ingredients, the combination of exhaust air and surrounding air may or may not result in a condensation trail.
In this particular instance, the presence of cirrus clouds indicates that the surrounding air was close to saturation with regard to ice, which suggests that the relative humidity in the upper stratosphere was reasonably high and that prime conditions existed for condensation trails to form and persist.
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