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Study Confirms that A research team analyzed sat- The data showed that an abun- More Aerosols Lead to ellite data of more than 2,400 dance of aerosols in the Heavier Rainfall convective systems. Satellite- can lengthen the life of a cloud sys- The connection between aero- based cloud aerosol data typically tem by 3–24 hours, depending on sols and extreme rainstorms has comes from polar orbiting satellites weather conditions in the vicinity. long been theorized, but a new that travel across the same location And the longer the persist study published in the Proceed- on Earth twice a day, but those sat- and the larger they grow, the more ings of the National Academy of ellites provide limited information rainfall they can produce. Sciences is the first to establish a about the lifetime of a convective “A cloud particle is basical- clear link between aerosols and cloud system. The new study took ly water and aerosols,” explains thunderstorm complexes known a unique approach by also utilizing the study’s lead author, Sudip as mesoscale convective systems, data from geostationary satellites Chakraborty, who recently re- which are the main sources of that fly at higher altitudes and ceived his Ph.D. from the Univer- in the tropics and remain in the same location rela- sity of . “It’s like a cell. The midlatitudes. The new study notes tive to Earth’s surface, allowing for aerosol is the nucleus and the water that the duration of these storm observations during storms’ entire is the cytoplasm. The more aero- complexes “can have a large influ- lives. The geostationary and polar sols you have, the more cells you ence on the variability of rainfall, orbiting satellite data were then get. And if you have more water, especially extreme rainfall that combined to provide a new per- you should get more .” causes flooding.” spective on the cloud systems. The research indicated that about 20% of the variability in the lifespan of a cloud system over ECHOES South Asia and Latin America This is like a bulldozer at 30 meters a second, going into could be attributed to the amount this water, and pushing it forward.” of aerosols in the atmosphere, with —Martin P. Lüthi of the University of Zurich (UZ), on the force cre- a lesser influence over Africa— ated when 900,000 cubic meters of ice broke from the Greenland glacier about 8% of the variability there is ‘‘called Eqip Sermia and plunged 200 meters into a fjord. Lüthi and fellow influenced by aerosols. UZ scientist Andreas Vieli studied the 2014 event and the tsunamis it caused—an immediate wave of about 50 meters in height, and another Mesoscale convective systems 10–15-meter-high tsunami that occurred less than 3 minutes later more can persist for more than 12 hours than 4.5 kilometers away. They found that the Eqip Sermia glacier has and stretch over several hundred accelerated its losses and its retreat from the coast to the center of the kilometers. The new paper estab- Greenland ice sheet in recent years, which has created a higher cliff face lishes the considerable impact that that extends as much as 200 meters out of the water within the fjord, lead- aerosols have on the lifespan of ing to tsunamis unprecedented in size. “I’ve never seen any glacier with such these systems, although coauthor a high front,” Lüthi states. “This is just not stable, that’s why it collapses Rong Fu of the University of Texas constantly.” While Lüthi surmises that the unusual shape of the glacier is temporary (the cliff face was only 50 meters high before 2012), he notes notes that meteorological condi- that the study, published recently in The Cryosphere, highlights the fact that tions—such as wind shear, relative “glaciers are changing like crazy, really rapidly. Everything changes, and humidity, and available convective people cannot rely on their experience from generations. Suddenly things energy—still have the greatest happen that nobody thought of before.” [Source: ] influence. [Source: University of Texas]

AMERICAN METEOROLOGICAL SOCIETY OCTOBER 2016 | 1775 Natural Circulation Perlwitz and colleagues stud- pattern influences cold winters in Driving Cold Northern ied multiple models to North America. Hemisphere Winters determine the effects of Arctic “These well-known circulation As warming of the Arctic region sea ice loss on both the Arctic patterns are the major drivers of has accelerated in recent decades atmosphere and temperature the wintertime temperature vari- and led to an increase in ice melt, patterns in the lower latitudes. ability in northern midlatitudes, a number of recent unusually They found that sea ice loss is and recent Arctic sea ice loss does chilly winters have occurred in in fact warming the Arctic, but not substantially affect them,” the Northern Hemisphere, giving determined that “recent Northern Perlwitz says. rise to the phrase “Warm Arctic, Hemisphere cold winters were The study found that the loss of Cold Continents” by some who the result of naturally occurring Arctic sea ice instead has a warm- have theorized the two are con- climate variations, and not due ing effect on typically cold air nected. However, new research to remote effects of Arctic sea ice masses that can periodically move published in Geophysical Research loss,” states lead author Lantao into the midlatitudes, leading to Letters suggests that “[i]t’s just by Sun of CIRES. fewer cold spells and less vari- chance and not because of Arctic For example, the researchers ability in daily temperatures. They sea ice loss or human-caused fac- found that “winter cooling trends suggest that “Warm Arctic, Warm tors that ‘Cold Continents’ has over Eurasia are accompanied by a Continents” is a more apt phrase happened more often in recent strengthening of the Siberian High, to describe human influence on years,” says coauthor Judith Perl- which brings more cold air from temperatures in the Northern witz of the Cooperative Institute the Arctic into central and eastern Hemisphere, as most of their model for Research in Environmental Asia,” Perlwitz explains. They runs depicted warming in both Sciences (CIRES). discovered that a similar natural regions. As a result, they expect

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