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News and Notes NEWS AND NOTES HOT TOWERS, STRONGER HURRICANES They are called hurri- canes in the Atlantic, typhoons in the West Pacific, and tropical cy- clones worldwide, but wherever these storms roam, the forces that de- termine their severity now are a little less mys- terious. NASA scien- tists, using data from the Tropical Rainfall Mea- suring Mission (TRMM) satellite, have found "hot tower" clouds are asso- ciated with tropical cy- clone intensification. Owen Kelley and Hurricane Bonnie's cumulonimbus storm clouds towered I I miles (18 km) above John Stout of NASA's the eye of the storm. The height in this image is exaggerated for clarity, and col- Goddard Space Flight ors correspond to surface precipitation from blue (light) to red (heavy). Center, Greenbelt, Mary- land, and George Mason University define a "hot tower" as three deaths, according to NOAA's To achieve their goal, Kelley and a rain cloud that reaches at least to National Hurricane Center. Stout needed to compile special the top of the troposphere, the Kelley says, "The motivation for kinds of global statistics on the oc- lowest layer of the atmosphere. It this new research is that it is not currence of hot towers inside tropi- extends approximately 9 miles enough to predict the birth of a cal cyclones. The only possible data high in the Tropics. These towers tropical cyclone. We also want to source was TRMM satellite, a joint are called "hot" because they rise to improve our ability to predict the effort of NASA and the Japan Aero- such altitude due to the large intensity of the storm and the dam- space Exploration Agency. "Many amount of latent heat. Water vapor age it would cause if it struck the satellites can see the top of a hot releases this latent heat as it con- coast." The pioneering work of tower, but what's special about this denses into liquid. Joanne Simpson, Jeffrey satellite's precipitation radar is that A particularly tall hot tower Halverson, and others has already it gives you 'X-ray vision' so you can rose above Hurricane Bonnie in shown that hot towers increase the see inside a hot tower," Kelley says. August 1998, as the storm intensi- chance a new tropical cyclone will To compile global statistics, the ra- fied a few days before striking form. Future work may use this dar needs to be orbiting the Earth. North Carolina. Bonnie caused association to improve forecasts of After compiling the statistics, more than $1 billion damage and a cyclone's destructive potential. Kelley and Stout found a tropical AMERICAN METEOROLOGICAL SOCIETY MARCH 2004 BAFFT I 327 cyclone with a hot tower in its eyewall was twice as likely to inten- SUN FASHION sify within the next 6 hours as a cy- While the ScotteVest jacket may look ordinary in terms of clone that lacked a tower. Kelley style, the interior contains 40 economically designed pockets and Stout considered many alter- that let the wearer discreetly carry electronic devices like cell native definitions for hot towers phones, PDAs, and MP3 players. This doesn't just sound like something out of a spy movie: the innovative jackets, sold by before concluding the 9-mile the International Spy Museum and ScotteVest, actually have height threshold was statistically been worn by the Secret Service. The problem with the significant. jacket, however, is that it does not contain any power source, so the new version, to launch this spring, has two snap-on LARGE-SCALE SALINITY solar energy panels. These feed into a hidden battery pack, to CHANGES IN THE OCEANS which almost any mobile device can plug into and recharge. Tropical ocean waters have become "As we move to an always-on environment, how can dramatically saltier over the past 40 people depend on their device if in 3 to 4 hours they are going to lose their charge?" says Scott Jordan, CEO of ScotteVest. years, while oceans closer to the The solar panels use CIGS (copper indium gallium diselenide) Earth's poles have become fresher, technology, an energy-efficient and highly sun-sensitive type of scientists report in the 18 December solar cell. Jordan says that the new jacket will retail for about 2003 issue of Nature. These large- $300, a $100 increase over the nonsolar version. scale, relatively rapid oceanic changes suggest that recent climate changes, including global warming, may be altering the fundamental fect global precipitation patterns thus are a key element of the glo- planetary system that regulates that govern the distribution, sever- bal water cycle. Because evapora- evaporation and precipitation and ity, and frequency of droughts, tion concentrates salt in the surface cycles fresh water around the globe. floods, and storms. It would also ocean, increasing evaporation rates The study was conducted by exacerbate global warming by rap- cause detectable spikes in surface Ruth Curry of the Woods Hole idly adding more water vapor—it- ocean salinity levels. In contrast, Oceanographic Institution; Bob self a potent, heat-trapping green- salinity decreases generally reflect Dickson of the Centre for Environ- house gas—to the atmosphere. And the addition of fresh water to the ment, Fisheries, and Aquaculture it could continue to freshen North ocean through precipitation and Science in Lowestoft, United King- Atlantic Ocean waters to a point that runoff from the continents. dom; and Igor Yashayaev of the could disrupt ocean circulation and The researchers analyzed a Bedford Institute of Oceanography trigger further climate changes. wealth of salinity measurements in Dartmouth, Canada. The oceans and atmosphere collected over recent decades "This study is important be- continually exchange fresh water. along a key region in the Atlantic cause it provides direct evidence Evaporation over warm, tropical Ocean, from the tip of Greenland that the global water cycle is inten- and subtropical oceans transfers to the tip of South America. Their sifying," said Elise Ralph, associate water vapor to the atmosphere, analysis showed the properties of director of the National Science which transports it toward both Atlantic water masses have been Foundation's physical oceanogra- poles. At higher latitudes, that wa- changing—in some cases radi- phy program, which funded the ter vapor precipitates as rain or cally—over the five decades for research. "This is consistent with snow and ultimately returns to the which reliable and systematic global warming hypotheses that oceans, which complete the cycle records of ocean measurements suggest ocean evaporation will in- by circulating fresh water back to- are available. crease as Earth's temperature does. ward the Equator. The process Curry, Dickson, and Yashayaev These issues are particularly im- maintains a balanced distribution observed that surface waters in portant as pressure on freshwater of water around the planet. tropical and subtropical Atlantic resources has become critical in The oceans contain 96% of the Ocean regions became markedly many areas around the world." Earth's water, experience 86% of saltier. Simultaneously, much of An acceleration of the Earth's planetary evaporation, and receive the water column in the high lati- global water cycle can potentially af- 78% of planetary precipitation and tudes of the North and South At- BAH5- MARCH 2004 .
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