No. 52: Jul-Aug 1987
August 1, 1985. Red Sea. Aboard the m.v. Botany Bay.
"At 1800 a crescent-shaped trace of spurious echoes appeared about 15 n. miles ahead of the vessel. This gradually developed, in an encirculating manner, until, by 1845 the echoes had totally surrounded the vessel. (See sketch.) The effect looked like, or could be likened to a plan view of a black island with sandy beaches around its perimeter. The echoes were significant with strong contrast and could even have been mistaken for land on the radar. The effect could not be removed or diminished by changing range scales, motion modes, gain, tuning or perhaps most significantly, altering the pulse lengths. An identical effect was observed on the vessel's independent ARPA radar. The Master commented that although false echoes were invariably encountered in this region, he had not seen one such as this, which actually 'encapsulated' the vessel within the PPI of the radar. By 1935 the false echoes had dissipated into isolated batches splayed randomly across the screen."
(Leslie, A.J.; "Radar Echoes," Marine Observer, 56:117, 1986.)
Comment. In the Red Sea and Persian Gulf, similar false echoes are often associated with bioluminescent phenomenon. For details, see category GLW in our catalog: Lightning, Auroras. Ordering information here.