A note on indirect wind speed measurements from ambient noise

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Abstract
Seven inverted echo sounders recovered in 1983 returned half hourly averages of the ambient noise at 10.25 kHz. The noise level recorded at the sounder nearest an in situ wind recorder (0°N, 28°10′W and 0°55′N, 29°20′W, respectively) is calibrated with the observed average daily wind speed. The resulting calibration curve of noise level versus observed wind speed estimates wind from noise with a standard deviation of 0.74 m s−1 for speeds greater than 3 m s−1 (The highest speeds observed were 9 m s−1. The calibration is used to estimate daily averaged wind speeds at a second sounder 1200 km to the west. The two derived wind series are coherent at periods greater than 12.7 days and in isolated frequency bands at shorter periods which correspond to known atmospheric waves. A difficulty in using these records to identify the time of the basin wide relaxation of the wind in the spring arises because of the 3 m s−1 sensitivity threshold of the ambient noise measurement.