Hurricanes Past, Present, and Future: New Perspectives
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This year is setting a record pace in tropical storm formation across the Atlantic Ocean. Below are updates on two new areas of hurricane research being pursued by scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, funded by the National Science Foundation.
"Hypercanes": A Possible Mechanism for Species Extinction?
Could a series of colossal hurricanes have led to the mass extinction of dinosaurs and other species? A computer model created by NCAR scientist Richard Rotunno and colleagues indicates that possibility. Rotunno, Kerry Emanuel of the Massachusetts Institute of Technology, and three other scientists argue that "hypercanes"-- theoretical superstrong hurricanes--may have been a crucial agent in past extinctions.
During the Late Permian period, about 245 million years ago, some 96 percent of all species disappeared. A later event extinguished 75 percent of all species. Giant meteors or volcanic eruptions have been cited as possible causes. The authors contend that neither type of event could inject enough long-lasting debris into the stratosphere to affect global climate on the scale needed for mass extinction. However, meteors or undersea eruptions might have been able to heat swaths of ocean a few tens of kilometers wide to temperatures as high as 50 degrees C (122 degrees F).
Rotunno took a hurricane model he created with Emanuel and tested it under these conditions. The superheated patches of ocean in the computer model quickly generated tropical cyclones with central pressures as low as 200 millibars and wind speeds as high as 300 meters per second (675 miles per hour, approaching the speed of sound). After about two days, the storms settled into a steady state with winds still around 340 mph. Such storms could produce vast sheets of stratospheric clouds that would alter radiation patterns and perhaps trigger ozone depletion, the scientists contend. Was Hurricane Andrew a Prelude to Future Coastal Disasters?
Hurricane Andrew raked south Florida in August 1992, causing some 40 deaths and $30 billion in damage. Yet it could easily have been worse. Had Andrew struck the Florida coast only 20 miles farther north, the damage could have been as much as $75 billion, according to several analyses. Had it struck areas along the East Coast or Gulf Coast where evacuation plans are inadequate, many more people could have died. These are among the messages contained in Hurricane Andrew in South Florida: Mesoscale Weather and Societal Responses. The report was recently done by Roger Pielke, a visiting political scientist at NCAR. Pielke provides an overview of the human factors that interacted with the physical reality of Andrew to create the disaster that occurred. The report is the first in a series in which Pielke examines several weather disasters, including the eastern U.S. "superstorm" of March 1993, and the Midwest flooding of that summer, from both scientific and societal viewpoints. Although improved warnings since the 1950s have reduced the death toll from U.S. hurricanes, damage costs continue to rise. Andrew struck an area (Dade County) with the country's most stringent hurricane building codes, yet the resulting damage made it clear that the codes were not being fully enforced, says Pielke. In fact, homes built since 1980 suffered more damage than did older homes. "Even with strict enforcement, Andrew still would have been the costliest hurricane in history. Thus, it is indeed frightening to consider the potential impacts of an Andrew like storm on other coastal communities." Despite improvements in warnings, large losses of life could still occur from a U.S. hurricane, according to Pielke. The evacuation of 700,000 people for Andrew was judged a success. However, the memory of that storm may result in more residents than necessary evacuating ahead of the next storm. Ironically, this could impede the flight of those most in danger. Due to a "post-Andrew effect," evacuation times in the Florida Keys might increase from 37 hours to as much as 80 hours for a major hurricane.
According to Pielke, the busy 1995 hurricane season is a "window of opportunity" for coastal communities to examine their vulnerability to severe weather. "The important questions are: How vulnerable are we? What decision processes are in place in regard to hurricanes? How can we use wisdom gained from 500 years of hurricane experience in North America, instead of ignoring or forgetting it?" In his report, Pielke includes a checklist that includes more than 176 important decisions each community vulnerable to hurricanes should make. "In some coastal areas, especially low-income ones," Pielke warns, "the evacuation plans are outdated."
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