A modified approach to scintillation index analysis of intensity

Intensity fluctuations of direct and refracted paths measured during a field test near San Clemente Island in August 2002 are presented. Signals used include 20 and 40 kHz CW pulses with 0.14‐ and 1.0‐ms durations. Source to receiver separation was 1 km. Towed CTD data, also collected during the experiment, is presented. Acoustic signals will be analyzed using a matched filter. Temperature variations will be computed as mean‐square fluctuations of the index of refraction. The intensity fluctuation records have lower scintillation indices than may be expected from the existing theory [e.g., Uscinsky et al., J. Acoust Soc. Am. 74 (1983)]. However, our frequencies are one to two orders of magnitude higher than those used in experiments for which this theory was developed and our propagation ranges are considerably shorter. More significantly, the acoustic data records are of considerably shorter duration (∼30 s) than previous experiments. To address the issue of the short record’s inability to detect larger ...