Heatmap from Scientific Research

Time series plot of mean volume backscattering strength ( S v ) at 125, 200 and 455 kHz for the entire observation period. The dashed vertical lines indicate (from left to right) the approximate dates of the first day of the autumn nautical twilight period, the beginning of the polar night, the end of the polar night and the last day of the spring nautical twilight period.

DOI