NCAR's support divisions have tended to grow in bursts of acquisition, development, and refinement. Last year the Scientific Computing Division took on a batch of new computers; this year the Atmospheric Technology Division is going through its own growth spurt. Several new facilities are in the works, others are being upgraded, and some new observational concepts may transform entire facilities over the next few years. See the article "ATD Collection" for a gallery featuring some of ATD's newest creations and the people behind them.
ATD director Dave Carlson. (Photo by Ginger Hein.) It's all done for the community--the atmospheric and geosciences research community. "I think and hope we're matched with what the scientists need," says Dave Carlson, ATD's director since last summer. "Two or three years ago we offered stand-alone surface weather stations, small surface radars, two small planes, and one big plane. Today that big plane (the Electra) takes a ground-based Doppler radar and puts it in the air, and we have two other big planes. Surface weather stations are blossoming into integrated systems. We've upgraded the radars. We're probing parts of the atmosphere we've never seen before."
Cataloging the full roster of ATD facilities could take volumes. But there are some common threads running through the most recent additions. One of those is the power of Global Positioning System (GPS) satellite navigation. Since the University NAVSTAR Consortium (UNAVCO) joined the UCAR family in 1990, its application of GPS technology to physical science measurement has found increasing use within the atmospheric sciences.
ATD's Surface and Sounding Systems Facility (SSSF) recently tested the use of GPS to track and measure winds with a radiosonde (balloon-borne instrument package), with potential applications in two new programs. One, the reference radiosonde, will allow several sensors from different manufacturers to fly on the same sonde, allowing direct intercomparisons for the first time. The other project is a GPS-based dropsonde (an instrument package dropped by parachute from an aircraft).
"When we first looked at the GPS test data, it appeared very noisy compared to data from conventional sondes," recalls Dave. "But it turns out that with GPS you're actually picking up the swinging of the radiosonde below the balloon as it ascends. So it definitely looks as if we have the precision we need."
SSSF also has created five prototype radiosonde ground stations for the National Weather Service to consider in the modernization of their sonde network. The system, known as NEXUS (Next-Generation Upper-Air Sounding System), will permit upgrades to GPS technology once GPS- based sondes become commercially available over the next few years. One of the NEXUS prototype stations includes an automatic launcher so that the observer need only load the sondes, set the calibration, and initiate a launch sequence. The system then launches the balloon at the preset time, freeing the operator from all-night duty.
Flux measurements rank high in priority at ATD these days. The portable automated mesonet (PAM) system used for years is being upgraded and refitted with the capacity to measure surface fluxes of heat, water vapor, and other quantities. Although the new PAM-III units will extend flux measurement to hitherto untapped regions, ATD plans to continue its Atmosphere-Surface Turbulent Exchange Research Facility (ASTER) to provide more comprehensive flux readings where needed. "ASTER can support many kinds of chemical fluxes," explains Dave. "It remains our central boundary-layer flux system. But it's too expensive to deploy ASTER in some projects. The PAM IIIs are designed to fill that niche."
NCAR's line-up of radars is undergoing near-complete transformation. CP-2, the center's primary S-band (10-centimeter wavelength) Doppler radar for years, is being phased into retirement. In its place will be S-POL, a highly portable S-band Doppler with advanced polarization capacity. Though CP-2 will be used this summer in a study of cumulus clouds over Florida, it's likely to be scavenged for parts soon thereafter. Mile High Radar, the Doppler unit stationed near Denver International Airport, is being maintained on a shoestring but seldom used. The CP-3 and CP-4 cloud physics radars are similarly quiescent at the Foothills Lab.
Meanwhile, ELDORA--the Electra Doppler radar, NCAR's foray into airborne radar funded jointly by NSF and the French government-- continues to develop. According to Dave, "ELDORA proved its concept in TOGA COARE [the Tropical Ocean and Global Atmosphere Program's Coupled Ocean-Atmosphere Response Experiment]. The real test of its design goals will be in a study of tornadoes this spring in Oklahoma [VORTEX, the Verification of the Origins of Rotation in Tornadoes Experiment]. It's the first experiment that will try its full capabilities. It'll really test the boundaries of what can be done with airborne radar."
With this much creative development on the loose, it's easy to see how two ATD groups and a UCAR staff member working on ATD projects won three of the Outstanding Performance Awards for 1994. "We definitely have gone through a sea change," reflects Dave. "I hope it reflects the way the science is going. In facility development, you can be too far in front or too far behind the curve. At times we've been one or the other. Global projects need integrated measurements, and that's the direction in which we are headed now." --BH