Cirrus clouds are our highest clouds; their delicate wispy strands are like an artist’s brushstrokes through the sky. During the day they are bright white and at dawn and dusk they can take on the hues of sunrise and sunset. But how are they made? New research reveals that some cirrus clouds are seeded by storms on the other side of the world, many thousands of miles away. This has implications for global heating as storm patterns shift.
Meteorologists have long recognised two types of cirrus cloud: “anvil” cirrus, which spread out from large storm systems, and “in-situ” cirrus, which seem to form on their own. Telling them apart is tricky, but by applying a new computer analysis to cloud satellite data, researchers spotted that in-situ cirrus emerged in response to major storm systems on the other side of the Earth.
Reporting in the American Geophysical Union Advances journal, they propose the storms generate massive atmospheric waves that travel across the equator, altering the temperature profile in the upper atmosphere and causing in-situ cirrus to emerge. Cirrus clouds are thought to allow sunlight through and trap heat in the atmosphere, resulting in a net warming effect, so now we need to understand if future changes in storm patterns will change the distribution and amount of cirrus clouds.
