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Tag: dust

  • Dusty Clouds Make More Ice

    Dusty Clouds Make More Ice

    Even when colder than its freezing point, water droplets have trouble freezing–unless there’s an impurity like dust that they can cling to. It’s been long understood in the lab that adding dust allows water to freeze at warmer temperatures, but proving that at atmospheric scales has been harder. But a new analysis of decades’ worth of satellite imagery has done just that. The team showed that a tenfold increase in dust doubled the likelihood of cloud tops freezing.

    Since ice-topped clouds reflect sunlight and trap heat differently than water-topped ones, this connection between dust and icy clouds has important climate implications. (Image and research credit: D. Villanueva et al.; via Eos)

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  • Saharan Dust

    Saharan Dust

    In late January, dust from the Sahara blew westward toward the Cabo Verde archipelago before turning northward toward Europe. During winter and spring, Saharan dust tends to stay at lower altitudes, where it can be carried by the northeast trade winds. In contrast, from late spring to early fall, dust rises higher, carried westward by the Saharan Air Layer; there, the dust can help suppress both the formation and intensity of the Atlantic’s hurricanes.

    On the left side of the image scant clouds trace von Karman vortex streets behind the archipelago, marking the atmospheric disruption caused by the rocky islands. (Image credit: L. Dauphin; via NASA Earth Observatory)

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    Earth’s Aerosols

    The motions of Earth’s atmosphere move more than just air and moisture. As seen in this animation built from NASA satellite data, the atmosphere also transports large amounts of small solid particles, or aerosols, such as dust. Each year the wind carries millions of tons of Saharan dust across the Atlantic, depositing much of it in the Amazon basin. This provides much needed nutrients like phosphorus to plants and animals in the Amazon; check out this video from the Brain Scoop to see what happens in areas that don’t receive these nutrients. Dust is only one of many sources for atmospheric aerosols, though. Sea salt, volcanic eruptions, and pollution are others. All of these aerosols serve as potential nucleation sites for raindrops or snowflakes, and their transport all around the globe by atmospheric winds means that seemingly local effects–like a regional drought or increased pollution in developing countries–can have global effects. (Video credit: NASA Goddard; submitted by entropy-perturbation)