ash clouds: severe storms can lift smoke into stratosphere

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Dec. 18 New England Journal of Medicine.In the other new study, researchers used

computerized tomography to spot calciumbuild-up in coronary arteries. Suchdeposits can reveal hidden atherosclerosis(SN: 9/13/03, p. 174).

Rheumatologist C. Michael Stein ofVanderbilt University School of Medicine inNashville and his colleagues report inthe same journal that 20 of 65 lupuspatients, but only 6 of 69 healthy volun-teers, had calcium deposits in a coronaryartery. The difference held up even whenthe team accounted for known heartattack risk factors.

Many lupus patients take anti-inflam-matory medication to suppress flare-ups oftheir symptoms. Roman and her colleaguesfound that lupus patients free of plaques intheir carotid arteries were more likely tohave taken strong anti-inflammatory drugs,such as prednisone, than were patients whohad plaques. The studies contradict a widelyheld opinion that long-term use of pred-nisone and other steroids accelerates ath-erosclerosis, says physician Bevra HannahsHahn of the University of California, LosAngeles in the same issue.

Hahn says the two new studies indicatethat “more aggressive control of [lupus]might help prevent atherosclerosis.”

Curiously, Roman says, blood analyses ofparticipants in her study didn’t show excessinflammatory proteins in lupus patientscompared with other volunteers. Therefore,while the findings solidify the link betweenlupus and atherosclerosis, she says, theydon’t pin down inflammation as its cause.

Inflammatory proteins are ephemeral,flooding the system during a lupus flare-up but subsiding otherwise, Stein says. Itcould be that lupus patients in the throes ofa flare-up were unlikely to volunteer forthese studies, he adds. —N. SEPPA

Ash CloudsSevere storms can liftsmoke into stratosphere

New field observations,satellite images,andcomputer models are steering some scientiststoward a surprising conclusion: A severethunderstorm, enhanced by the heat from ahuge forest fire, can boost soot, smoke, andother particles as high as the lower strato-sphere. The newly suspected transfer ofaerosols to high altitudes could require sig-

nificant changes in computer models ofatmospheric circulation and climate.

Most of Earth’s weather—and most of itsair pollution—resides in the troposphere,the layer of atmosphere that extends fromthe planet’s surface to altitudes betweenabout 8 and 13 kilometers. Previous stud-ies suggested that most particles floating inthe stratosphere, the next-highest atmos-pheric layer, come from volcanic eruptionsor are generated on the spot by high-flyingaircraft, says Pao K. Wang of the Universityof Wisconsin–Madison.

Scientists generally hadn’t suspected thatthunderstorms can transport particlesacross the troposphere’s well-defined upperboundary, but a wealth of observations ischallenging that view, Wang told an audi-ence last week in San Francisco at the fallmeeting of the America Geophysical Union.

Consider the flurry of carbon-bearing par-ticles encountered by a high-flying NASAresearch jet early this year. On flights nearKiruna, Sweden, instruments detected suchaerosols at concentrations of up to 1 micro-gram per cubic meter. That’s more than30 times the amount that can be accountedfor by commercial aircraft, says DarrelBaumgardner of the National AutonomousUniversity of Mexico in Mexico City. Elevatedconcentrations of carbon monoxide andother gases in air samples bolster the notionthat the particles came from forest fires, hesays. Baumgardner presented his findings atlast week’s San Francisco meeting.

Also, satellite observations last summershowed that hundreds of fires across theNorthern Hemisphere sometimes strength-ened nearby thunderstorms, which thenapparently pumped immense plumes ofsmoke and soot into the stratosphere. Someof those long-lasting plumes could be tracedintact for distances exceeding 5,000 km,which suggests that many of the particleswere in the stratosphere, riding high aboveweather systems that could have broughtthem back to the ground, says Michael D.Fromm, a meteorologist with the researchfirm Computational Physics in Springfield,

Va. Similar plumes from intense fires nearCanberra, Australia, reached the strato-sphere in January 2003, he says.

Computer models of ash columns spout-ing from a large forest fire show that theextra heat can invigorate storm clouds thatpass over or form nearby, says Wang. Strongupdrafts in the storms can then carryplumes of smoke and soot that burst intothe stratosphere, the simulations indicate.

Even small numbers of particles in thestratosphere can have significant effects onclimate, says Wang. For instance, Baum-gardner’s analyses suggest that the con-centrations of sooty aerosols found overSweden could boost absorption of incom-ing solar radiation in the lower stratospherein winter months by as much as 15 percent.

No current models of atmospheric cir-culation or climate incorporate the effectsof fire-enhanced thunderstorms injectingparticles or gases into the stratosphere,says Wang. —S. PERKINS

Crystal Clear Liquid crystal sensor plays nature’s game

Thanks to billions of years of evolution,cellsare remarkably adept at detectingpathogens or toxic chemicals in the envi-ronment. Taking advantage of this naturalsurveillance capability, researchers haveincorporated components of cell mem-branes into sensors to sniff out dangerouschemical and biological agents.

Led by chemical engineer Nicholas L.Abbott at the University of Wisconsin–Madison, the researchers placed a layer ofphospholipids—the fatty acids constitutingcell membranes—on top of a liquid crystal.“These are the same liquid crystals you findin laptop-computer displays,” says Abbott.

In the new sensing scheme, the lipidsattach themselves to the rod-shaped liquidcrystal molecules, which lie perpendicular

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SCIENCENEWSThis Week

ASH FOUNTAIN A computer model of a fire-enhanced thunderstorm shows a plume of ashand soot (arrow) rising above cloud tops and into the stratosphere.

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