Intense storms have become more frequent and longer-lasting in the Great Plains and Midwest in the last 35 years.
Understanding how storms changed in the past is an important step towards projecting future changes.
"These storms bring well over half of the rain received in the central U.S. in the spring and summer," said atmospheric scientist Ruby Leung.
Previous research had found more heavy springtime rain falling in the central United States in recent decades, but scientists did not know what types of storms were causing the increase. To do so, the team worked out a way to identify storms called mesoscale convective systems. This type of storm develops from smaller convective storms that aggregate to form the largest type of convective storms on Earth. They are best detected using satellites with a bird's eye view from space. They transformed well-established satellite detection methods into a new technique that he then applied to rainfall measured by radars and rain gauges for the past 35 years. This allowed the researchers to identify thousands of the large convective storms and their rainfall. The results showed the frequency of very long-lasting ones increased by about 4 percent per decade, most notably in the northern half of the central region -- just below the Great Lakes. The researchers rated the storms that produced the top five percent of rainfall as extreme events and saw that extreme events have become more frequent in the last 35 years. The researchers analyzed the region's meteorological environment and found that the Southern Great Plains warms more than the ocean does. This difference in temperature creates a pressure gradient between the Rocky Mountains and the Atlantic Ocean that induces stronger winds that push moisture up from the Gulf of Mexico. The warmer and moister air converge in the Northern Great Plains, where it falls in massive storms. These massive storms are occurring more often and producing heavier rainfall.
No comments:
Post a Comment