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

• Published in: Journal of geophysical research. Atmospheres 2024-11, Vol.129 (21), p.n/a
• Main Author: Loeffler, Scott D.
• Format: Article
• Language: English
• Subjects: Atmosphere; convection; Correlation; Estimates; Fallout; Helicity; Hodographs; Hydrometeor size; Hydrometeors; Meteorological radar; Polarimetric radar; precipitation; Radar; Radar signatures; Rain; Raindrops; Reflectance; Storms; Weather radar; Wind; Wind profiles; Winds
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2024JD041175

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 ZDR $\left({Z}_{DR}\right)$ and specific differential phase KDP $\left({K}_{DP}\right)$. Previous work has shown a strong correlation between the mean storm‐relative wind in the sorting layer and the separation between regions of enhanced ZDR ${Z}_{DR}$ and KDP ${K}_{DP}$ 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. Plain Language Summary Large raindrops fall through a given layer of the atmosphere more quickly and, therefore, spend less time in the layer compared to small drops. This impacts weather radar variables and two of them are featured in this study. A simple model of raindrop fallout and motion is used to show that the change in a radar signature between two heights serves as a good estimate for the wind between those two heights. Additionally, these estimated winds can be used to calculate estimates of metrics related to the vertical wind profile. Key Points The storm‐relative wind profile can be estimated by analyzing hydrometeor size sorting signatures The change in the size sorting signature between two heights is highly correlated with the storm‐relative wind between those heights Metrics such as shear and storm‐relative helicity can be estimated using the radar‐derived estimates of the storm‐relative wind profile