A High-Frequency Radio Acoustic Sounder for Remote Measurement of Atmospheric Winds and Temperature

Abstract

The Radio Acoustic Sounding System (RASS) is used to remotely measure atmospheric temperature profiles. The technique used for these measurements is Doppler tracking of a short, high-intensity acoustic pulse with an RF (electromagnetic) radar. By measurement of the acoustic pulse propagation speed, temperature can be calculated as a function of altitude. The Stanford University RASS operates at an acoustic frequency of 85 Hz. Because of this low frequency and the necessity of high system gain, the unit is too large for mobile applications. Our theoretical analyses show, however, that the RASS could operate at much higher acoustic frequencies and still provide data to altitudes of ~1 km even during periods of moderate to strong atmospheric turbulence. These theoretical analyses have now been supported experimentally. A RASS operating with an acoustic frequency of 1 kHz not only provided Doppler data to altitudes of 1 km, but it also was able to provide a measure of horizontal winds over the same range. These experimental results came from a brief effort to support our theoretical studies. Future experiments could well extend the profiling range and versatility of the high-frequency RASS. Ultimately, we hope that our work will lead to a transportable system to be used for collecting real-time data on atmospheric winds and temperatures.