Conventional instruments are not available for measurement of air temperature at remote places, or for the spatial mean of the component for a certain direction of wind speed at a certain height above the ground over a line of some hundred meters or more. The possibility of the use of sonic means for this purpose was investigated, through the development of a sonic model device and its field test.
The model device consists of a 20-W output sound transmitter, a receiver and a computing apparatus with a recorder. The field test was carried out along the path of the transmitter and receiver horns at 2.5m height above the ground with 550m baseline length for air temperature and 300m for wind speed component. The sound transit time is measured and then converted automatically into spatial means of air temperature and of wind speed component with the
compensation for the effect of water vapor pressure. The products are then corrected manually for the effects of wind speed the vertical ambient air emperature gradient.
For reference measurements, thermister thermometers and three-cup anemometers were placed along the baseline, whose measurements were referred to for verification of those by the sonic device.
From the results of the field test, it became clear that the measurement of the mean air temperature several meters above the ground by the sonic method must be based on a more accurate knowledge of the mechanism of sound propagation and that the baseline length should be less than 550 m.