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November 21, 2013 — In less than two years, the University of Wyoming’s King Air research aircraft will expand its weather forecasting and research capabilities with the use of an advanced form of lidar that will be able to study the behavior of storms at night.
Zhien Wang, a professor in the UW Department of Atmospheric Science, and Perry Wechsler, a UW senior research scientist and chief engineer of the King Air, recently received a $1.2 million National Science Foundation (NSF) grant to develop a Multi-function Airborne Raman Lidar (MARLi). The Raman Lidar will simultaneously measure profiles of temperature, water vapor mixing ratio, clouds and aerosol. Lidar, an acronym for light detection and ranging, is an optic remote sensing technology that can detect and measure molecular aerosols and cloud droplets in the atmosphere.
Wang’s proposal, titled “MRI: Development of a multi-Function Airborne Raman Lidar (MARLi) for Atmospheric Process Studies” was approved for funding by the NSF in July. UW matched the NSF grant, providing $515,000. The funding project started Sept. 1.
“As envisioned, MARLi has the potential to revolutionize a range of atmospheric processes studies,” Wang says. “Immediate applications of MARLi include participating in several field projects being planned to study convective initiation, cloud-environment interactions, mesoscale dynamics, and atmospheric boundary layer over land and oceans. Such studies are fundamental to improving the climate simulations and our capability to forecast weather and air quality.”
On a dark and stormy night
During 2015, the Raman Lidar will be used for a research project dubbed Plains Elevated Convection at Night (PECAN). Data from this project, which is pending NSF approval, will be shared with the federal agency, Wang says.
“The King Air will fly at night,” says Al Rodi, professor and head of UW’s Department of Atmospheric Science, and who serves as the King Air’s facility manager. “They will look at factors that make storms occur at night.”
Convective clouds during the night can spawn major hail storms and tornados, Wang says.
Traditionally, the environments of such storms have been examined using small weather balloons or radiosonde, dropsonde and aircraft flight-level measurements. However, these methods cannot offer needed spatial and temporal structures of fast-moving storm environments, Wang says.
“With the new lidar, we will be able to profile the temperature, water vapor and aerosol continuously below the aircraft and down to the surface,” Wang says.
“What you will see going on is the structure of the water vapor and temperature in two dimensions. And that’s never been done before,” Wechsler says. “We’ll be getting a fine structure, from the ground up to 20,000 feet, depending on the flight level. If you can get that picture in real time, it is very valuable.”
“It’s been done on water vapor, but not temperature,” Wang adds. “Both, together, are important.”
This will be possible because the Raman Lidar will include 12-14 channels. Each channel records unique atmospheric information, such as temperature, water vapor, aerosols and clouds.
“We’re on the edge of becoming more quantitative,” Wechsler says. “We’ll be getting pictures no one has seen before.”
Observational capabilities provided by the Raman Lidar will address many of the important measurement gaps identified during the recent NSF Lower Atmospheric Observing Facilities (LAOF) workshop, Wang says. The university King Air has been a part of the LAOF since 1987. Under a cooperative agreement, the NSF provides $1.75 million in base funding annually to UW.
From the ground up
In his campus lab, Wang is building the Raman Lidar with Wechsler, the departmental engineering staff and some UW graduate students.
“It’s (Raman Lidar) home-brewed,” Rodi says, “He’s (Wang) going to get the parts and put it together.”
To build the Raman Lidar, some parts will be ordered (some as far away as Germany) while others will be designed on campus, Wang says.
“This is a pretty complicated instrument,” he says.
The major challenge of MARLi development is the design of a system capable of reliably providing high-quality measurements in the challenging environment of a research aircraft, Wechsler says. Meeting this challenge requires reductions in system power, size and weight while being able to operate in an environment of constant vibration, Wang says. King Air’s current remote sensing capabilities include radar and lidar.
“We’ll have a radiator to eliminate excess heat” from the instrument, Wechsler says. “The current lidar requires 1,500 watts of power. The new one will use 6,000 watts of power. It’s a huge difference.”
While the Raman Lidar will be designed to fit the King Air, Wechsler says it also will be available for installation on the NSF/National Center for Atmospheric Research (NCAR) C-130 research aircraft. The technology, used in concert with other LAOF instruments, will allow NSF-supported researchers to address science questions that are limited by current observational capabilities.
One UW graduate student will help develop the lidar and all graduate students in Wang’s research group will participate, to some extent, in instrument development and testing.
The lidar system will be incorporated into the Atmospheric Instrumentation course offered at UW. The Raman Lidar will provide students with hands-on experience using state-of-the-art atmospheric remote sensing.
“The eventual availability of MARLi to the wider atmospheric science community will greatly increase the number and diversity of students utilizing the equipment,” Wang says. “The potential impact of this instrument will be transformative.”
Zhien Wang, a UW professor of atmospheric science, and Perry Wechsler, a UW senior research scientist and chief engineer of King Air, examine a small version of Raman Lidar Wang built with an NSF CAREER Grant. The two are currently creating a larger version that will be used for studies of nighttime storms on the King Air research aircraft.