Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Some of the biggest raindrops on record found in both clean and dirty air

13.07.2004


If raindrops on roses are among your favorite things, University of Washington researchers have encountered some monster drops that could change your mind.

On two occasions, separated by four years and thousands of miles and in very different conditions, raindrops were measured at sizes similar to or greater than the largest ever recorded. The largest ones were at least 8 millimeters in diameter, about the same as the largest previously observed, and were possibly a centimeter – about four-tenths of an inch or one-fourth the diameter of a golf ball – according to findings published today in the online edition of Geophysical Research Letters, a journal of the American Geophysical Union.

As they fall toward earth, raindrops don’t have the cliché teardrop shape, said Peter Hobbs, a UW atmospheric sciences professor. Instead, they are shaped more like a parachute, or a jellyfish.



"Most of the water is around the rim of the drop, while the upper part of the drop is a very thin film of water," Hobbs said.

When air forces through the thin film at the top, large drops break up into many smaller drops. Large drops also can break up when they collide with other drops. In laboratory conditions, breakup usually happens when the drops reach about 5 millimeters, or about one-fifth of an inch, in diameter. In clouds, when drops reach that size they generally break up in collisions with other drops.

"That’s why it’s so rare to see a raindrop of 5 millimeters or more on the ground, because it would mean the drop had avoided collisions with the many other drops in a cloud," Hobbs said.

Yet the UW Cloud and Aerosol Research Group recorded raindrops of at least 8 millimeters, and perhaps a centimeter, during research flights through cumulus congestus clouds spawned by a burning forest in Brazil in 1995. Giant raindrops also were recorded during a flight through cumulus clouds in clean marine air over the Marshall Islands in 1999.

Hobbs and Arthur Rangno, a UW atmospheric sciences research meteorologist, are co-authors of the paper documenting the findings. The work was supported by funding from the National Science Foundation and the National Aeronautics and Space Administration.

The scientists speculate the giant raindrops in the polluted air above the burning Amazon forest could have formed around large ash particles, while those in the Marshall Islands might have been spawned by particles of sea salt.

It is not unusual to see large drops in clouds formed in clean marine air because there are fewer particles on which the water can collect, Hobbs said. But smoky air typically produces small raindrops because there are so many particles for the water to condense upon, so it is unclear why the huge raindrops formed over Brazil. He noted that collisions of drops can produce larger drops that then gather up additional small drops as they fall, much as a drip does as it slides down a window pane. That could be what happened in the Brazil storm clouds, as a few favored raindrops fell through, and collected, smaller drops present in large concentrations within particular regions of the clouds.

The scientists discovered the giant raindrops as they culled mountains of data recorded when the research group still operated its own aircraft. The aircraft was sold in 2002, but scientists still are going through data from a number of missions, including campaigns in Africa and the United States, as well as Brazil and the South Pacific.

"We collected so much data on those flights, recording thousands of events a minute, and it will take years to analyze all of the information," Hobbs said. "We just discovered the giant drops by accident when we were looking for something else."

Vince Stricherz | EurekAlert!
Further information:
http://www.washington.edu

More articles from Earth Sciences:

nachricht Six-decade-old space mystery solved with shoebox-sized satellite called a CubeSat
15.12.2017 | National Science Foundation

nachricht NSF-funded researchers find that ice sheet is dynamic and has repeatedly grown and shrunk
15.12.2017 | National Science Foundation

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>