ZDR ARC Area And Intensity as a Precursor to Low Level Rotation in Supercells
Abstract
It has been hypothesized that some measurable properties of ZDR arcs in supercells may change in the minutes prior to tornadogenesis and tornadogenesis failure, and that ZDR arc area will change with SRH and can be used as a real-time proxy to estimate SRH. Output form the Cloud Model 1 (CM1) along with a polarimetric emulator is used to simulate ZDR arcs in 9 tornadic and 9 non-tornadic supercells. A random forest algorithm is used to automatically identify the ZDR arcs. Finally the inflow sector SRH is calculated at times when ZDR arcs are identified. To analyze the change in intensity and area a comparison between the average ZDR value inside and outside of the arc, as well as the spatial size of the arc and storm was done. Model calculated SRH is then compared to these metrics. It has also been observed that hail fallout complicates the automatic identification of ZDR arcs. In this study, three experiments are run where the simulated ZDR arcs are produced. One using all categories of hydrometeors, one where wet growth and melting of hail is excluded, and one excluding the contribution to ZDR from the hail hydrometeor category. The same analysis as above is repeated for all three experiments. Finally observed ZDR arcs are analyzed to see if these results are applicable to the real world.
Degree
Ph.D.
Advisors
Dawson, Purdue University.
Subject Area
Atmospheric sciences|Meteorology
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