Radar Antenna Replacement Effort Begins at Barrow

 
Published: 15 December 2007

On November 28, 2007, ARM operations and engineering staff braved -15°F weather to install the new radar antenna at Barrow.  After lifting the antenna via crane onto the roof of the skydeck, the gloves had to come off to securely fasten all the tiny connecting screws and bolts—brrrrr!

For estimates of cloud boundaries, there is no better capability than the millimeter wave cloud radar (MMCR). This sophisticated radar is part of the standard instrument suite at all of the permanent ARM sites except for Atqasuk, Alaska. With the 3-meter antenna at the ARM Southern Great Plains (SGP) site more than 11 years old, and the 2-meter antennas in the Arctic and tropics ranging from 8 to 10 years old, all have begun showing signs of wear and tear. In late November, ARM engineering staff replaced the MMCR antenna at the North Slope of Alaska site in Barrow, beginning a complex-wide effort to replace all the radar antennas throughout the user facility.

The MMCR antenna transmits pulses of millimeter-wave energy into the atmosphere, and receives the return signals that bounce back from cloud particles, bugs, or other objects in the atmosphere. These “retrievals” are used to determine cloud tops, bottoms, reflectivity, and vertical velocities. In the past few years, signs of wear began to appear on the antenna’s reflector surface, as well as corrosion on the radar antenna’s support struts. And finally, the water repellent coatings for the radomes began to lose their effectiveness. Because refitting, recalibrating, and shipping the old antenna would cost almost as much as installing new equipment, the ARM sites will all receive new antennas in the coming two years. The new antennas include improved technology for radar echo measurements that help to remove return signals from insects and are useful for precipitation studies. The replacement effort also includes upgrading the radar’s data acquisition systems at SGP and Barrow from analog to digital processors for increased sensitivity and efficiency.