Radio Acoustic Sounding System (RASS) for Temperature ProfilingThe original concept for an operational NPN envisioned the Doppler radar profiler as part of an integrated upper-air remote sensing system to measure wind speed and direction, temperature, and humidity. The Demonstration Division is now involved in a long-term effort to help meet the NPN productivity goals, which can be fulfilled, in part, through the addition of RASS to produce temperature profiles and the Global Positioning System (GPS) to measure atmospheric water vapor. (The photo of the White Sands Missile Range profiler site in Figure 33 shows multiple observing systems: a profiler surface observing system, a profiler radar antenna, a RASS acoustic transducer, and a GPS water vapor antenna.)
The propagation velocity of the RASS acoustic signal is measured by the wind profiling radar. This measurement is converted to a virtual temperature (similar to the actual temperature except for a small offset due to water vapor in the air). Although the temperature measurements produced by the eight RASS units maintain an accuracy better than 1oC, the altitude to which they can measure is limited. The stronger the lower tropospheric horizontal wind, the greater the likelihood that the acoustic signal will be carried out of the radar beam, the reason for placing acoustic sources at all four corners of the wind profiling radar. RASS measurements with the 404-MHz profilers typically extend up to 3 to 5 km above ground.
Figure 33. White Sands Missile Range profiler site with multiple observing instruments.
This page maintained by: Wilfred von Dauster Last modified 15 May 1997