The arrangement of the lines in this image may look like an ocean tic-tac-toe game, but in fact the grid can be explained by a relatively general atmospheric property. Ship’s footprints are long, narrow clouds that form in the sky over the ocean as water vapor condenses around small particles in the ship’s exhaust.

The Visible Infrared Imaging Radiometer Suite (VIIRS) This image was obtained from the Finland-NPP satellite after the ships on December 7, 2021. That day, traces revealed several shipping lanes crossing the waters of the Pacific coast of North America.

Aerosol emissions from ships occur with or without clouds. But the presence of these numerous small particles can become more apparent in natural color images as the particles interact with low-level clouds and make them brighter. This is because aerosols allow more and smaller cloud droplets to form, causing more surfaces to reflect light.

Scientists have been studying the phenomenon for decades and studying the complex interactions between aerosols and clouds to find out what these interactions mean for climate change. Scientists, for example, want to know the extent to which the traces of ships can lead to the planet cooling.

In recent years, scientists have used machine learning to identify the traces of ships – some of which may go unnoticed by the human eye – and to classify different types of clouds around the planet. The technology will help grow the collection of cloud images available for scientific research.

NASA Earth Observatory image based on Joshua Stevens’ NASA EOSDIS VIIRS data LANCE, GIBS / Worldview, and Finland’s national polar partnership. The story of Kathryn Hansen.