Measurement Of Ocean Surface And Bottom Backscattering Strengths In The Northwestern Atlantic Ocean PDF Download

Experimental measurements of ocean surface and bottom backscattering strengths were carried out in the northwestern Atlantic Ocean during July and August 1990. The experiment used ship and air deployed explosive charges to provide ensonification of the ocean surface and bottom over a range of low frequencies up to 1 kHz. Overall, the surface backscatter results agreed well with the Ogden-Erskine curves, matching the predicted dependence on wind speed, grazing angle, and frequency. At two sites northeast of the Grand Banks, the surface backscattering strengths appeared to be dominated by volume backscattering caused by fish. The bottom backscattering strengths were observed to have considerable variation in level (up to 17 dB) between different sites. As a function of grazing angle, most of the bottom backscattering strength curves paralleled the Mackenzie curve for the grazing angles between 30 and 50 deg. A moderate frequency dependence of approximately 3 dB was observed. Comparisons of the bottom backscattering strengths with the Damuth 3.5 kHz echo- character province types yielded no consistent correlations. Comparisons with archival results for the same region yielded general agreement within 6 dB. Comparison of the ship-based and airborne techniques that they yielded comparable backscattering strengths to within 5 dB.