Cloud streets and detoursOne of the spectacular atmospheric features that is d…

Cloud streets and detours

One of the spectacular atmospheric features that is difficult to recognize from the surface but that stands out when pictured from orbit is seen here – cloud streets. Cloud streets appear to satellites as long chains of clouds covering substantial areas on the planet; when viewed from the surface or even from a plane, they often just appear as patchy clouds and it requires the full, distant view to be able to recognize them.

Cloud streets form when there are extensive, almost straight-line winds with no obstacles, as can occur over the ocean or over an ice cap. With no obstacles in the way, wind blows in a fairly straight direction over long distances and as the air moves, heating from the sun causes small-scale convection cells to set up. Where air rises it cools and water condenses to form clouds, where air sinks in these cells the sky is cloud-free. These patterns are stretched out by the straight line winds into the long cloud streets that here cover the northernmost Atlantic Ocean.

These cloud streets run into one obstacle – the volcanic rocks of Jan Mayen Island. When straight-line air runs into an obstacle, it flows around to each side of the obstacle and then has to turn to fill in the space behind. This turning creates vortices that alternate from one side to the other in the wake behind it.


Image credit: NASA/MODIS