Vorticity from Line-of-Sight Lidar Velocity Scans

Abstract

A method is presented to compute the spanwise vorticity in polar coordinates from 2D vertical cross sections of high-resolution line-of-sight Doppler wind lidar observations. The method uses the continuity equation to derive the velocity component perpendicular to the observed line-of-sight velocity, which then yields the spanwise vorticity component. The results of the method are tested using a ground-based Doppler lidar, which was deployed during the Terrain-Induced Rotor Experiment (T-REX). The resulting fields can be used to identify and quantify the strength and size of vortices, such as those associated with atmospheric rotors. Furthermore, they may serve to investigate the dynamics and evolution of vortices and to evaluate numerical simulations. A demonstration of the method and comparison with high-resolution numerical simulations reveals that the derived vorticity can explain 66% of the mean-square vorticity fluctuations, has a reasonably skillful magnitude, exhibits no significant bias, and is in qualitative agreement with model-derived vorticity.