An unusually high number of ship tracks are visible in the clouds off of the coasts of France and Spain in these Moderate Resolution Imaging Spectroradiometer (MODIS) images from the Aqua satellite and Terra satellites, captured within hours of each other on January 27, 2003. Very small airborne particles emitted in the exhaust of large ships (and airplanes) attract water particles, acting as “seeds”for clouds, or cloud condensation nuclei, as they are scientifically named. Continued accumulation forms the thin, streaky clouds that are pictured in these images. As the ships moved about the East Atlantic, these clouds formed, leaving a visible, though impermanent, record of where the ships had recently been.
Ship tracks can last for hours, and give clues as to their age and the relative speed of the ships by their shape and diffuseness. The faster the ship, the narrower, longer, and less diffuse the ship track will be. Slower ships will leave shorter, wider, and more diffuse ship tracks.
When ships emit tiny airborne particles into a clean, relatively stable and very humid air-mass, conditions are ideal for cloud formation, and ship tracks form. Consequently, these types of clouds are most common over major shipping lanes on large bodies of water, such as the northern Atlantic and Pacific Oceans, though they have even been observed over the North American Great Lakes. Bands 1 (650 nm), 4 (555 nm), and 3 (469 nm) were used to create this true-color image.