Comments on “Identifying Z_DR Columns in Radar Data with the Hotspot Technique”

In convective storms, there are often enhanced regions of differential radar reflectivity Z_DR above the 08C level known as Z_DR columns. The Z_DR column serves as an updraft proxy and therefore is commonly used in both severe storm research and operations, which motivates the development of algorithms to automate their detection. A recent article details the development of a new algorithm to identify Z_DR columns. In addition, the article includes intercomparisons between the new algorithm and other similar algorithms that have been developed for community use. However, the comparisons do not use real output from the previously developed algorithms as they were designed. In this article, we present a detailed description of several algorithms used to identify Z_DR columns and provide additional context to Z_DR column algorithm comparative cases by including output from the real algorithms. We also discuss the difficulty in objectively evaluating Z_DR column algorithms given the lack of direct observations of vertical velocities in convective storms.