Laser Radar System Takes First Measurements of Upper Atmosphere Temperatures

CHAMPAIGN, Ill., April 3 – A sensitive laser radar (lidar) system, first deployed over Okinawa, Japan, to observe meteor trails during the 1998 Leonid meteor shower, has now been used to probe temperatures in the upper atmosphere over both geographic poles. According to a report printed in the Arpil 1 issue of Geophysical Research Letters scientists at the University of Illinois used a specially designed lidar system to obtain the first measurements of upper atmosphere temperatures, iron densities and polar mesospheric clouds over the North and South poles.

"Measuring temperature profiles over the poles is essential for validating global circulation models and for providing a baseline for assessing the impact of global warming over the coming decades," said team leader Chester Gardner, a UI professor of electrical and computer engineering. "Until now, we were limited to measurements taken with balloon-borne sensors to altitudes of less than 20 miles."

In collaboration with scientists at The Aerospace Corp. and the National Center for Atmospheric Research, Gardner and his UI colleagues – professor George Papen, research scientist Xinzhao Chu and graduate student Weilin Pan – developed a more robust lidar system for measuring temperature profiles from the middle of the stratosphere (about 20 miles up) to the lower thermosphere at the edge of space (about 70 miles above Earth). The system uses two powerful lasers operating in the near-ultraviolet region of the spectrum and two telescopes to detect the laser pulses reflected from the atmosphere.