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Finding Tiny Particles In Hurricanes May Help With Predictions
Greenbelt - Apr 30, 2002 NASA-funded scientists are looking at microscopic ice particles inside hurricanes to determine if they contribute to the storm's strengthening or weakening. Researchers have discovered that greater numbers of ice particles higher up in a hurricane reflect more energy from the Sun out to space, creating a temperature difference that helps power the hurricane. The particles could also indicate a loss of energy into the surrounding atmosphere. During a flight into Hurricane Humberto in 2001, researchers identified a large number of ice particles up to 7 millimeters in diameter in the upper reaches of the storm, around 39,000 feet high. The research was part of CAMEX-4 (The Convection And Moisture EXperiment), a joint effort between NASA, the National Oceanic and Atmospheric Administration (NOAA) and a number of universities. "We've found that a high concentration of small particles at the top portion of a hurricane are very reflective, and they send more energy back to space than previously thought," said Andrew J. Heymsfield, researcher from the National Center for Atmospheric Research (NCAR), Boulder, Colo., and a lead author on a paper on the experiment. Large concentrations of small ice crystals can reflect more sunlight and can lead to strong cooling near the tops of hurricanes, creating more of a temperature contrast between the bottom and top of the storm. That contrast of air temperatures could possibly contribute to its strength, just as a cold front moving into warm, moist air triggers thunderstorms. "Updrafts of wind in hurricanes are generally pretty small, so some researchers did not expect large (up to 7 millimeters) particles, which generally form at warm temperatures, to exist at higher altitudes," Heymsfield said. Because large particles weigh more, they fall faster than small particles, and small particles can evaporate.
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