Novel instrument can make sharpest measurement of ice crystals in clouds

Washington, July 18 : Scientists have created an instrument which would help determine the sharpest measurement of ice crystals that are found in high-altitude clouds, which will help with climate change predictions.

The data produced using this instrument likely will help improve computer models used to predict climate change.

Among the hundreds of factors climate scientists must take into account in modeling weather, the nature of clouds is one of the most important and least understood.

The best researchers could do in the past to measure cloud ice crystals was to try to record images of them, but for crystals below 25 microns, the images were too blurred to allow accurate determination of the crystal's shape.

Researchers need to know the shape and sizes of these ice crystals because these properties influence how much incoming sunlight gets absorbed in the atmosphere and how much gets reflected right back out into space.

This, in turn, can have a huge impact on the magnitude of possible global warming or cooling.

Now, scientists from the University of Hertfordshire and the University of Manchester in the United Kingdom and Colorado State University in the United States have developed an optical scattering instrument that can evaluate the size of the crystals in a different way.

Using this instrument, the researchers have been able to determine sizes and shapes of cloud ice crystals all the way down to the tiniest micron levels.

The research team actually has built two versions of the instrument: one designed to operate on ground-based cloud simulation chambers or to operate in the fuselage of research aircraft; the other, an aerodynamic version that fits under the wing of the aircraft and measures the cloud particles directly as the aircraft flies through the cloud.

Neither instrument attempts to make a full image of the ice crystal, since this would suffer the same resolution limits of existing instruments.

Instead, they record the detailed pattern of scattered light from each individual crystal and then interpret these patterns using either theoretical models or by comparison with recorded patterns from known crystal shapes.

From this data, a crystal census of varying sizes and shapes can be made.

"The new instruments should help map out a more complete understanding of complex crystal shapes found in atmospheric clouds, especially cirrus clouds, which on any day can cover more than 20 percent of the Earth's surface," said one of the researchers, Hertfordshire scientist Paul Kaye.

"We believe that this optical scattering instrument could help climate modelers reduce one of the greatest areas of uncertainty in interpreting the influence of clouds and in making more accurate climate predictions," he added.

ANI