The research of functioning of the regional system of underwater navigation support in different hydrological conditions

Abstract

The paper presents the results of experimental and numerical studies of the regularities of formation of acoustic fields generated by low-frequency pulse signals propagating from the shelf into the deep sea. The results of an experiment conducted in the Japan Sea in April 2014 are discussed in comparison with the results obtained in August 2006, on the same acoustic track, with distances between corresponding points of more than 100 km. In April hydrological conditions on the coastal zone of the acoustic trace and in the upper layer of the deep part of the sea were characterized by a relatively weak (~0.35 s−1) negative vertical gradient of sound speed, while in August 2006 it was ~1.5 s−1. Experimental and numerical studies showed that the effect of acoustic «mudslide» in the conditions of weak negative gradient of sound speed is also apparent, but the structure of the acoustic field which is trapped by the underwater sound channel has a more complicated structure with a stretched time impulse response. However, it’s ordered, stable and well identifiable structure in all randomly selected points for measurement on the acoustic trace may provide the establishment of effective underwater navigation systems of GLONASS and GPS type for a season of spring hydrology.