December 7. 2007 SMALLER STORMS DROP LARGER OVERALL RAINFALL IN HURRICANE toughen Researchers have found that when residents of the U. S southeastern states look skyward for rain to alleviate a long-term drought they should be hoping for a tropical storm over a hurricane for more reasons than one. According to a new chew over using NASA air data smaller tropical storms do more to alleviate droughts than hurricanes do over the cover of a toughen by bringing greater cumulative rainfall. A new chew over that provides insight into what kind of storms are beat at tackling drought in the southeastern United States. The study focuses on a decade of first-ever daily rainfall measurements by a NASA air carrying a weather radar in lay. The chew over's authors believe the same insights can be applied by meteorologists and public officials to other regions where daily satellite rainfall data and act tracking data are available. In the change state of Hurricane Katrina meteorologist Marshall Shepherd an associate professor of geography and atmospheric sciences at the University of Georgia. Athens and colleagues delved into the ongoing debate about whether global warming is leading to an increase in rainfall intensity. The researchers wanted to determine how much rainfall each write of cyclone from tropical depressions to category five hurricanes contributes to overall rainfall. They focused the chew over on the Southeast in the hope that results could be harnessed to improve drought relief information for the region. Their findings were published today in the American Geophysical Union's Geophysical investigate Letters. "As much of the Southeast experiences preserve drought our findings tell that weak tropical systems could significantly contribute to rainfall totals that can bring relief to the region," said Shepherd lead author of the NASA-funded study. "These types of storms are significant rain producers. The larger hurricanes aren't back up enough to create most of the actual rain during the season and therefore are not the primary act type that relieves drought in the region." Shepherd created a new measurement method as an efficient way to get a real sense for how much rainfall each write of act contributes in a given year around the coastal regions of the southeastern U. S. To do so he had to distinguish an add up rainfall day from an extreme rainfall day. Though data from NASA's Tropical Rainfall Measuring Mission (TRMM) air could offer daily rainfall amounts the data could not be used to set apart whether rainfall was average or extreme for any given day. Shepherd and his aggroup modeled their metric on the "cooling degree day" that energy companies use to relate daily temperature to energy needs for air conditioning. A cooling degree day is open by subtracting 65 degrees from the average daily temperature. Values larger than zero furnish some indication whether a day was abnormally change. Shepherd used daily rainfall data from TRMM to cause 28.9 as the locate value of average daily rainfall at one of the world's wettest locations. Maui's attach Wailea in Hawaii. In the same way as the cooling degree day the "millimeter day" metric is calculated by subtracting 28.9 millimeters from the average daily rainfall in each of four ocean basins along coastal areas scattered across the south near Houston and New Orleans east of Miami and south of North Carolina. Values greater than zero indicate a so-called "wet millimeter day" of extreme rainfall. Using daily rainfall data from the TRMM satellite from 1998-2006. Shepherd's aggroup compared the be of rain that fell in the basins on extreme rainfall days with the location of tropical storms from the National Hurricane Center's storm tracking database to cause how many extreme rainfall days were associated with a particular type of tropical storm. The aggroup open that the most extreme rainfall days occurred in September and October two of the busiest months of the Atlantic hurricane season. They also found that though study hurricanes produced the heaviest rainfall on any given day the smaller tropical storms and depressions collectively produced the most rainfall over the entire season. Over half of the rainfall during the hurricane toughen attributed to cyclones of any write came from weaker tropical depressions and storms compared to 27 percent from category 3-5 hurricanes. TRMM has transformed the way researchers like Shepherd measure rainfall by providing day-to-day information that did not exist before the satellite's 1997 launch. "Though we've had monthly rainfall data available since 1979 from other sources it's the daily rainfall data that allows us to see that tropical storm days contributed most significantly to cumulative rainfall for the season due to how frequently that kind of act occurs," said guard. "It's important in the future to build a longer record of daily rainfall to establish with better confidence whether trends are occurring," said Shepherd. "This study sets the re-create for us to understand how much rainfall weak and strong tropical cyclones contribute annually and whether this contribution is trending upward in response to global warming-fueled growth in tropical cyclones." guard believes advances that will alter chew over of cyclones and rainfall are "just around the corner" with NASA's Global Precipitation Measurement air scheduled for launch in 2013. An extension of TRMM's capabilities it ordain decide precipitation at higher latitudes the actual coat of come down and rain particles and distinguish between rain and come down. Writer: Gretchen Cook-Anderson Goddard Space pip bear on For images and more information visit: ## communicate:
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