Picturesque Clouds off Greenland

Picturesque Clouds off Greenland

A few times every spring, the skies over the Labrador Sea fill with row after row of long, parallel bands of cumulus clouds. The magnificent organization of these clouds, known as cloud streets, was on full display when this image was acquired on April 19, 2022.

Captured with the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite, the image shows cloud streets sweeping over the open water between Labrador, Canada, and southwest Greenland.

The appearance of cloud streets indicates that strong, cold winds were blowing toward the southeast over comparatively warmer water. In springtime, sea ice has already entered the melting season, but there is still plenty of ice over land and sea to produce very cold, dry air. There is also enough open water from which that air can draw moisture and form clouds.

The pattern is the result of the ice-chilled air being warmed by the ocean surface and forming strong currents of upward moving air, or thermals. The moist air rises until it hits a temperature inversion, which acts like a cap and causes the air to roll over and form parallel cylinders of rotating air. On the upper side of these cylinders (the rising air), clouds form. Along the downward side (descending air), skies are clear.

The wide view reveals even more compelling cloud patterns. Notice that the cloud streets are adjacent to an area of vortices off the southeast coast of Greenland. According to Gunilla Svensson, a meteorologist at Stockholm University, those clouds were likely related to a narrow band of high winds known as a “tip jet.” A tip jet is thought to be caused by winds that accelerate as they are forced to go around the steep topography of Cape Farewell.

NASA Earth Observatory images by Joshua Stevens, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview. Story by Kathryn Hansen.

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