Retrieving Estimates of the Storm-Relative Wind Profile From the Vertical Variation of Hydrometeor Size Sorting Signatures

Abstract

Raindrop fall speed increases with raindrop size. Because larger raindrops fall through a given layer of the atmosphere more quickly compared to smaller raindrops, they spend less time in the layer and, therefore, have less time to be acted on and advected by the storm-relative winds. This results in hydrometeor size sorting which impacts the polarimetric radar variables such as differential reflectivity $\left(Z_{DR}\right)$ and specific differential phase $\left(K_{DP}\right)$. Previous work has shown a strong correlation between the mean storm-relative wind in the sorting layer and the separation between regions of enhanced $Z_{DR}$ and $K_{DP}$ at the bottom of the sorting layer. This study leverages this finding, along with a simple size sorting model, to construct radar-derived estimates of the storm-relative wind profile. The radar-derived “pseudo-hodographs” are well-correlated with the magnitude and direction of the corresponding storm-relative wind profiles. Further, these radar-derived estimates of the storm-relative winds are used to calculate estimates of shear and storm-relative helicity, which also exhibit a strong correlation.