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For more information on these science news and feature story tips, please contact the public information officer at the end of each item at (703) 292-8070. Editor: Josh Chamot Contents of this News Tip:
New Model Enhances National Hurricane Prediction SystemScientists know that while most hurricanes rapidly weaken after landfall, mainly because their source of evaporating water dries up, some storms are able to persist and cause further damage. Researchers have now found that under certain conditions, inland water sources less than two-feet-deep are enough to sustain storms and lead to further damage. Supported by the National Science Foundation (NSF), oceanographer Isaac Ginis of the University of Rhode Island (URI) Graduate School of Oceanography and colleagues studied the effect of land-surface water on hurricane intensity. Ginis, along with URI oceanographer Lewis Rothstein, developed a computer model to predict the hurricane intensity. They coupled their model with one created by the National Oceanic and Atmospheric Administration's (NOAA) Geophysical Fluid Dynamics Laboratory to provide a more efficient framework to consider atmosphere-ocean interaction during storms, and more accurately predict storm intensity. The coupled model has become an official component of the national hurricane prediction system used to forecast Atlantic and Gulf of Mexico tropical storms and hurricanes. Previous studies of land-falling hurricanes used fixed underlying surface conditions. Ginis' study used a newer model that includes surface temperature changes and their influence on surface heat, hurricane structure and hurricane intensity. The scientists also used a range of water depths and surface roughness to allow an array of surface conditions. The study showed that during hurricane landfall over water-covered land, large local surface cooling occurs near the hurricane core region. The surface cooling reduces evaporation, considerably reducing the hurricane intensity. The reduction depends on the presence and depth of surface water. With a two-foot layer of surface water, the hurricane will maintain its intensity, but over dry land, the storm collapses. Ginis, along with URI oceanographer Lewis Rothstein, developed a computer model to predict the hurricane intensity. They coupled their model with one created by NOAA's Geophysical Fluid Dynamics Laboratory to provide a more efficient framework to consider atmosphere-ocean interaction during storms, and more accurately predict storm intensity. The coupled model has become an official component of the national hurricane prediction system used to forecast Atlantic and Gulf of Mexico tropical storms and hurricanes. [Cheryl Dybas] Hurricane Isidore Proves Perfect Subject for Study of Rapidly Intensifying StormsThe season's second tropical whirlwind to reach hurricane strength gave hurricane hunters the opportunity to monitor and measure a tropical storm as it rapidly intensifies. Supported by NSF, scientist Nick Shay of the University of Miami, along with atmospheric researcher Peter Black of NOAA's hurricane research division, are studying how deep layers of warm surface water in the ocean help hurricanes to rapidly intensify - one of the most difficult situations to forecast and one of the most dangerous for coastal residents. The scientists dropped a series of ocean probes from hurricane hunter aircraft as Isidore gained strength. Released in Isidore's projected path in the southern Gulf of Mexico, the probes measured ocean temperature and currents down to 200 meters (about 650 feet), the depth at which hurricane winds usually churn up colder water and cool the overall temperature of water below the storm. "When Isidore is over the Gulf Stream, its warm water extends below to great depths, not allowing Isidore's winds to cool the surface," said Shay. "That in turn keeps the heat reservoir intact and allows further intensification of a hurricane." Shay and Black will measure differences in the ocean's temperature structure during three phases of tests. The results, say the scientists, will clarify the ocean's role in hurricane intensification and may lead to a greater ability to predict when and how much a storm may intensify - a challenge considered to be the next step in hurricane forecasting. [Cheryl Dybas] Lowered Methane Emissions Could Reduce Both Global Warming and Air PollutionReducing methane gas emissions by half could alone reduce air pollution and global warming, according to a new study by scientists at Harvard University, Argonne National Laboratory, and the Environmental Protection Agency. In the NSF supported-study, researchers directly link methane to the production of ozone in the troposphere, the part of the atmosphere that extends from the Earth's surface upwards about 7.5 miles. Ozone is the primary constituent of smog, and both methane and ozone are significant greenhouse gases. In the October issue of Geophysical Research Letters, Arlene M. Fiore of Harvard and her colleagues simulated effects of methane on climate using emissions projections from the United Nations Intergovernmental Panel on Climate Change (IPCC). From their findings, the researchers suggest that global reduction of methane emissions will simultaneously decrease ozone pollution and greenhouse warming. The researchers find that reducing methane emissions from human activities by 50 percent would have a greater impact on global tropospheric ozone than would a comparable reduction in nitrogen-oxide emissions from human activities. Reducing surface nitrogen-oxide emissions does effectively improve air quality by decreasing surface ozone levels, but this impact tends to be local, and does not yield as much benefit from greenhouse warming. Human-derived sources of methane include rice production, leaks of natural gas from pipelines and herds of cattle. Natural sources include wetlands, termites, oceans and methane trapped in ice on the sea floor. A baseline study in 1995 showed that 60 percent of methane emissions to the atmosphere were the result of human activity. However, according to the researchers, aggressive emission controls aimed at lowering ozone-based pollution both in the United States and Europe could be offset by rising emissions of methane and nitrogen oxides from developing countries. The study was also funded by the Environmental Protection Agency (EPA), and the National Aeronautics and Space Administration (NASA). [Cheryl Dybas]
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