And no raindrop can fall faster than its "terminal speed"--its speed when the downward force of gravity is exactly the same as the upward air resistance. Now, a team of U.S. and Mexican researchers has found that it ain't necessarily so.
Some smaller raindrops can fall faster than bigger ones. In fact, they can fall faster than their terminal speed. In other words, they can fall faster than drops of that size and weight are supposed to be able to fall. And that could mean that the weatherman has been overestimating how much it rains, the scientists say.
"Existing rain models are based on the assumption that all drops fall at their terminal speed, but our data suggest that this is not the case," explains Raymond Shaw, a physicist at Michigan Technological University in Houghton and a member of the research team. "If rainfall is measured based on that assumption, large raindrops that are not really there will be recorded."
understanding of the physics of rain and improve the accuracy of weather measurement and prediction.
Shaw, Alexander Kostinski, also of Michigan Tech, and Guillermo Montero-Martinez and Fernando Garcia-Garcia of the Universidad Nacional Autonoma de Mexico (National University of Mexico) in Mexico City, will publish their findings Saturday, June 13, in the American Geophysical Union's journal, Geophysical Research Letters.
To study the raindrops, they used optical array spectrometer probes and a particle analysis and collecting system. They also modified an algorithm, or computational formula, to analyze raindrop sizes.
The scientists found clusters of raindrops falling faster than their terminal speed, and as the rainfall became heavier, they saw more and more of these unexpectedly speedy drops. Images revealed that the "super-terminal" drops come from the break-up of larger drops, which produces smaller fragments all moving at the same speed as their parent raindrop and faster than the terminal speed predicted by their size.
"In the past, people have seen indications of faster-than-terminal drops, but they always attributed it to splashing on the instruments," Shaw says. He and his colleagues took special precautions to prevent such interference, including collecting data only during extremely calm conditions.
This research was supported in part by the National Science Foundation.Title:
Alexander B. Kostinski: Department of Physics, Michigan Technological University, Houghton, Michigan, USA;
Raymond A. Shaw: Department of Physics, Michigan Technological University, Houghton,Michigan, USA;
Fernando Garcia-Garcia: Posgrado en Ciencias de la Tierra y Centro de Ciencias de la Atmosfera, Universidad Nacional Autonoma de Mexico, Circuito de la Investigacion Cientifica, Mexico City, Mexico.Citation:
Res. Lett., 36, L11818, doi:10.1029/2008GL037111.
Peter Weiss | American Geophysical Union
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences