Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

What is a cloud? Scientists still searching for a clear-sky definition

06.12.2005


All through the ages, humans have dreamily gazed at those shape-shifting cotton-balls floating gently across the sky-the clouds.



Atmospheric scientists-Earth’s professional cloud-gazers--have learned a great deal about clouds over the decades, particularly with the advent of satellites during the 1960s and 70s. But despite years of research and the emergence of increasingly sophisticated tools, scientists are still at odds over one of the most basic issues of all: how to define a cloud.

"The problem is that what we define a cloud as depends on the type of instrument we’re using to define it," says atmospheric scientist Steven Ackerman, the director of the Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin-Madison. It’s an issue Ackerman will discuss today (Dec. 8, 2005) at the fall meeting of the American Geophysical Union, which runs Dec. 5-9.


It is critical to define and measure clouds accurately, notes Ackerman, because their patterns and formations play an important role in shaping both weather forecasts and longer-term climate predictions. Clouds are also a crucial part of Earth’s hydrological and energy cycles, both regulating atmospheric precipitation and determining how much solar energy reaches the Earth.

A number of issues, however, make measurements of planetary cloud cover a very "fuzzy" matter, Ackerman says. Orbiting satellites, for instance, make different types of cloud observations from space. In one approach - known as "active sensing" - satellites discern the presence of clouds by directing energy of varying wavelengths at successive sections of the atmosphere.

The problem, says Ackerman, is that varying that energy threshold by just 3-4 percent can significantly alter cloud cover measurements. Different satellites also introduce variation, with readings differing by up to 5-10 percent between instruments. "It’s like assigning grades," says Ackerman. "If you score 90 and above you get an A; but what if someone gets 89.8 and gets a B? Is that fair? Well that’s the same problem with measuring clouds."

Cirrus clouds - wispy, long formations that almost look like smoke - are particularly problematic to define. As these clouds taper off into nothingness, scientists often struggle to define the point at which they cease to be clouds, says Ackerman. Furthermore, as satellites scan consecutive blocks of the atmosphere, making readings can get pretty tricky, he adds. "An [observation] area may contain different types of clouds or may be half-full of cloud or packed with thick cloud-so then we’re asking: is that a cloud or not a cloud?"

Over the years, scientists have periodically gathered to refine the science of cloud measurements. It may be time again for that larger discussion, says Ackerman.

Steven Ackerman | EurekAlert!
Further information:
http://www.ssec.wisc.edu

More articles from Earth Sciences:

nachricht Monitoring lava lake levels in Congo volcano
16.05.2018 | Seismological Society of America

nachricht Ice stream draining Greenland Ice Sheet sensitive to changes over past 45,000 years
14.05.2018 | Oregon State University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

Im Focus: Dozens of binaries from Milky Way's globular clusters could be detectable by LISA

Next-generation gravitational wave detector in space will complement LIGO on Earth

The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...

Im Focus: Entangled atoms shine in unison

A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.

The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...

Im Focus: Computer-Designed Customized Regenerative Heart Valves

Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.

Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...

Im Focus: Light-induced superconductivity under high pressure

A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.

Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

 
Latest News

Supersonic waves may help electronics beat the heat

18.05.2018 | Power and Electrical Engineering

Keeping a Close Eye on Ice Loss

18.05.2018 | Information Technology

CrowdWater: An App for Flood Research

18.05.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>