Detection of “Invisible Waterspout” Using 3D Scanning Doppler Lidar

Abstract

A three-dimensional coherent Doppler lidar (3D-CDL) and an interval camera were used to detect a cyclonic “invisible waterspout” very close to the sea surface near Ikeshima island, Nagasaki Prefecture, on 21 December 2010. High-resolution 3D-CDL images revealed that the waterspout had a subscale vortex. The deduced core diameter of the waterspout (subscale vortex) was 234 m (105 m), and the vorticity was 0.17 s^-1 (0.32 s^-1). The estimated maximum wind speed of the waterspout was about 17 m s^-1, which falls into the category of an F0-scale tornado. Analysis of the 3D-CDL and C-band Doppler radar data shows that the waterspout and two vortices were observed along a gust front ahead of the parent storm.