The Radio Acoustic Sounding System (RASS) is used to measure temperature and winds in the lower atmosphere. RASS is the first and the only remote temperature profile measuring system with a considerably fine resolution in temperature and altitude. The technique used for these measurements is Doppler tracking of short, strong acoustic pulse with a CW radar. The radio waves reflected from acoustic wavefronts produce a relatively small spot on the ground by the focusing effect of the spherical wavefronts. The wind profile can be measured by tracking the motion of the spot of the radio echo with a receiving antenna network and receivers. Further, the temperature profile can be measured from altitude distribution of the sound velocity which is obtained from the Doppler shift frequency of the radio echo. This report reviews an outline of the RASS operation (Chap. 2), recent development of RASS and the relevant observational results in Japan (Chap.3) and the brief summary of experimental studies on RASS in the world (Chap. 4).
