Monitoring Experiment Hopes to Save Water

This article touts the Laser aspect of this story, but what is behind the idea is better monitoring to save water.

Laser experiment hopes to save farm water

Seventy-six years after the invention of the modern sprinkler helped revolutionize farming, lasers may revolutionize it again.

By JOHN ROGERS

Associated Press Writer

LOS ANGELES —

Seventy-six years after the invention of the modern sprinkler helped revolutionize farming, lasers may revolutionize it again.

Jan Kleissl and a handful of his students at the University of California at San Diego think technology using laser beams might lead to a better way to conserve the millions of gallons of water sprayed each year on thirsty crops.

The monitoring is done by a Scintillomter.

He and his team are using a large aperture scintillometer to study how much water crops lose to evaporation and the peak times that water disappears.

The hope is to give farmers a more accurate, up-to-date reading of how efficiently their crops are using water than current technology allows.

"What's new about our approach is the monitoring side of it," Kleissl said by phone from his office. "We're trying to improve on that."

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But Kleissl's team hopes to give farmers more valuable information by using the scintillometer, which focuses laser beams across a farm field and records fluctuations of the refractive index of air that is caused by such things as changes in temperature and humidity.

What the device sees is similar to the waves in the air that people see emanating from the pavement of a highway on a hot day. But the scintillometer sees those waves in much greater detail. The hope is farmers can eventually use the lasers to more accurately measure the amount of irrigated farm water lost to evapotranspiration

What is a scintillometer?

Scintillometer

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A Large Aperture Scintillometer (transmitter) for measurement of the sensible heat flux over long distances at Wageningen University measurement site

A Scintillometer is a scientific device used to measure small fluctuations of the refractive index of air caused by variations in temperature, humidity, and pressure. It consists of an optical or radio wave transmitter and a receiver at both ends of an atmospheric propagation path. The receiver detects and evaluates the intensity fluctuations of the transmitted signal, called scintillation.

The magnitude of the refractive index fluctuations is usually measured in terms of Cn^2, the structure constant of refractive index fluctuations, which is the spectral amplitude of refractive index fluctuations in the inertial subrange of turbulence. Some types of scintillometers, such as displaced-beam scintillometers, can also measure the inner scale of refractive index fluctuations, which is the smallest size of eddies in the inertial subrage.

Scintillometers also allow measurements of the transfer of heat between the Earth's surface and the air above, called the sensible heat flux [1]. Inner-scale scintillometers can also measure the dissipation rate of turbulent kinetic energy and the momentum flux.

The term Scintillometer has been used, in its original sense (though relatively infrequently today except in a few specialized instances (such as the mining industry for checking drillcores for the presence of uranium)) to refer to a Scintillation counter, which measures ionizing radiation.