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

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Researchers shoot for success with simulations of laser pulse-material interactions

29.03.2017 | Materials Sciences

Igniting a solar flare in the corona with lower-atmosphere kindling

29.03.2017 | Physics and Astronomy

As sea level rises, much of Honolulu and Waikiki vulnerable to groundwater inundation

29.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>