Velocity Distance Azimuth Display (VDAD)—a new framework to examine linear and non-linear wind fields using single Doppler radar data

Single Doppler velocity has been extensively used to infer qualitative characteristics of the horizontal wind fields. Some quantitative information of linear wind fields, such as the divergence, deformation, and average winds, can be extracted using the Velocity Azimuth Display (VAD) algorithm. Caya and Zawaski (1992) discussed the implications and limitations of a non-linear wind fields on the VAD algorithm. This paper introduces a new framework, Velocity Distance Azimuth Display (VDAD), to examine the characteristics of linear and non-linear wind fields by analyzing a field composed of the radial velocity multiplied by the distance of that gate (i.e., r*Vr). Analyzing this new parameter, r*Vr, possesses several advantages over analyzing Vr. First, r*Vr is represented in Cartesian coordinate systems while Vr is represented in spherical coordinate systems. Therefore, non-linear wind fields represented in polynomial form can be approximated by curve fitting in Cartesian coordinate directly without the need to perform multiple VAD analysis. Second, r*Vr has the property of a velocity potential where its gradient is a proxy of the local wind vector. Third, the signature of the wind field is easier to identify in the r*Vr space. For example, a constant wind field in the r*Vr space is a set of parallel lines while a linear wind field is quadratic form in r*Vr space. We will present the mathematic framework of VDAD. The characteristics of r*Vr will be illustrated from several analytical linear and non-linear wind fields. The potential advantages of VDAD to deduce characteristics in mesoscale wind fields over the VAD will be discussed.