A ZDR column detection algorithm to examine convective storm updrafts

Jeffrey C. Snyder, Alexander V. Ryzhkov, Matthew R. Kumjian, Alexander P. Khain, Joseph Picca

Research output: Contribution to journalArticlepeer-review

58 Scopus citations


Observations and recent high-resolution numerical model simulations indicate that liquid water and par- tially frozen hydrometeors can be lofted considerably above the environmental 0°C level in the updrafts of convective storms owing to the warm thermal perturbation from latent heating within the updraft and to the noninstantaneous nature of drop freezing. Consequently, upward extensions of positive differential re- flectivity (i.e., ZDR ≥ 1 dB)-called ZDR columns-may be a useful proxy for detecting the initiation of new convective storms and examining the evolution of convective storm updrafts. High-resolution numerical simulations with spectral bin microphysics and a polarimetric forward operator reveal a strong spatial asso- ciation between updrafts and ZDR columns and show the utility of examining the structure and evolution of ZDR columns for assessing updraft evolution. This paper introduces an automated ZDR column algorithm designed to provide additional diagnostic and prognostic information pertinent to convective storm now- casting. Although suboptimal vertical resolution above the 0°C level and limitations imposed by commonly used scanning strategies in the operational WSR-88D network can complicate ZDR column detection, ex- amples provided herein show that the algorithmcan provide operational and research-focusedmeteorologists with valuable information about the evolution of convective storms.

Original languageEnglish (US)
Pages (from-to)1819-1844
Number of pages26
JournalWeather and Forecasting
Issue number6
StatePublished - 2015

All Science Journal Classification (ASJC) codes

  • Atmospheric Science


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