Dust in the clouds
At any given time, cirrus clouds — the thin wisps of vapor that trail across the sky — cover nearly one-third of the globe. These clouds coalesce in the upper layers of the troposphere, often more than 10 miles above the Earth’s surface. Cirrus clouds over dust source region Photo: Peter DeCarlo/Drexel University Cirrus clouds influence global climate, cooling the planet by reflecting incoming solar radiation and warming it by trapping outgoing heat. Understanding the mechanisms by which these clouds form may help scientists better predict future climate patterns. Now an interdisciplinary team from MIT, the National Oceanic and Atmospheric Administration (NOAA), and elsewhere has identified the major seeds on which cirrus clouds form. The team sampled cirrus clouds using instruments aboard high-altitude research aircraft, analyzing particles collected during multiple flights over a nine-year period. They found that the majority of cloud particles freeze, or nucleate, around two types of...