Ship Trails and Jet Contrails on NOAA Weather Satellite Images

Ship trails are low, warm, condensation clouds similar to fog that are seeded by the exhaust of ships, most likely the sulfer dioxide in Bunker fuel. The animation below spans FIVE HOURS and the movement of a number of ships can be followed. The trails are pushed by low light low level winds and distorted quickly. Ship trails can be seen on visible satellite images but not on infrared images because they are warm and nearly the same temperature as the sea surface.

The image below shows condensation trails from ships covering thousands of miles west of California
click on images for larger view

Below is a rare image showing both ship contrails and jet contrails
The contrails are very different.
Ship contrails are low, warm, "fog", seeded by sulphuric acid droplets and unburned hydrocarbons from ship exhaust.
Jet contrails are very high, extremely cold ice crystals.

The image above is shown again below in two versions, infrared on the left and visible on the right.
Jet contrails are most easily seen in the infrared images because their cold temperature makes them very bright white. They are usually hard to spot in visible images because they are narrow and do not persist very long. Jet contrails appear over both land and sea, and are much straighter than ship trails because the are so short lived.
Ship trails last for hours or days and twist into many shapes as they are blown by light low level winds. Their shape does not denote the ship's path since the wind may move the trails hundreds of miles. Ship trails are large and bright in the visible light images but invisible on the infrared because they are low and almost the same temperature as the sea surface.

Same image, infrared channel left and visible channel right

This is another close-up of the same visible image as above showing the jet contrails in more detail. Close inspection reveals the contrails as well as their shadows cast on lower level clouds.

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