Detecting clouds from both sides now

Mar 13, 2012

Researchers have developed a more precise method to detect the boundary between clouds and clear air, by exploiting the swinging motions of a weather balloon and its payload.

"Bows and flows of angel hair, and ice cream castles in the air;" we've looked at clouds that way. But the interface between clouds and clear air isn't as well-defined as these imaginative shapes might lead us to believe. Detecting that hazy line can help scientists to better understand the processes that lead to cloud formation, which is important for good and climate modeling. Now from the University of Reading in the United Kingdom have designed a sunlight-measuring tool that uses the natural swinging and spinning of a rising weather balloon to distinguish clouds from clear air and may provide higher-resolution measurements of cloud boundaries than is currently possible. The researchers describe their device in a paper published in the American Institute of Physics' journal .

Traditional cloud detection using weather balloons relies on measurements of temperature and relative humidity. The Reading researchers reasoned that they could sense clouds optically, using a simple and inexpensive design: a light sensor carried on a . This sensor responds to the , producing a maximum reading when pointing directly at the Sun in clear air but reduced readings at oblique angles to the Sun. As the sensor swings beneath a moving balloon, its orientation to the Sun changes continually, resulting in large fluctuations in the sensor's light intensity readings in cloudless conditions. But inside a cloud – where is roughly the same in all directions – the fluctuations become much smaller. The team showed that cloud edges could be detected by looking for an abrupt change in the size of these fluctuations.

Laboratory experiments demonstrated that the new instrument worked consistently over the wide range of temperatures that weather balloons encounter. In test flights, the optical technique was able to detect cloud boundaries with greater precision than traditional relative humidity measurements alone. Though this method works best to detect the upper boundaries of clouds, the researchers say that the new system could also be used to determine lower boundaries of clouds in broken cloud conditions or for high-level clouds.

Explore further: SMAP will track a tiny cog that keeps cycles spinning

More information: "Balloon-borne disposable radiometer for cloud detection" has been published in the Review of Scientific Instruments.

add to favorites email to friend print save as pdf

Related Stories

Study may produce better weather forecasts

Aug 11, 2005

Accurately forecasting rain reportedly will become easier thanks to a study of clouds conducted by the University of Leeds and University College London.

New tool clears the air on cloud simulations

Oct 26, 2011

(PhysOrg.com) -- Climate models have a hard time representing clouds accurately because they lack the spatial resolution necessary to accurately simulate the billowy air masses.

Scientists seek clear-sky definition of clouds

Dec 06, 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 ...

Recommended for you

SMAP will track a tiny cog that keeps cycles spinning

25 minutes ago

When you open the back of a fine watch, you see layer upon layer of spinning wheels linked by interlocking cogs, screws and wires. Some of the cogs are so tiny they're barely visible. Size doesn't matter—what's ...

Satellite witnesses developing US nor'easter

17 hours ago

National Weather Service forecasters have been tracking a low pressure area that moved from the Midwest into the Atlantic Ocean today, and is expected to become a strong nor'easter that will bring blizzard ...

Study finds how weathermen get their forecasts wrong

21 hours ago

The night before the Israel Defense Forces' 1976 mission rescuing over 200 hostages from hijackers in Entebbe, Uganda, Tel Aviv University's Prof. Pinhas Alpert, then head of an Israel Air Force base forecasting ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.