S149 Examining the Changes in The Tornado Debris Signature with different Debris Types

Sunday, 10 January 2016
Hall E ( New Orleans Ernest N. Morial Convention Center)
Allison T. LaFleur, Lyndon State College, Lyndonville, VT; and N. T. Atkins

This research examines how differential reflectivity (ZDR), correlation coefficient (RHOHV), and reflectivity (DBZ) change as a tornado interacts with different types of debris. High resolution mobile Doppler radar data and a detailed aerial damage survey of the 2013 El Reno OK tornado are used to examine these variables along the damage path over vegetative fields and when the tornado impacts houses and buildings. An initial qualitative analysis was done to visualize how ZDR, RHOHV, and DBZ change over time inside the tornadic debris signature (TDS). A statistical analysis of 13 different times was performed to determine exactly how the different variables changed over time. After the tornado hits the houses the ZDR and RHOHV values decrease and the reflectivity increases. The RHOHV values decrease because leaves and dirt and other light debris has a more uniform shape than larger debris such as houses. The ZDR values depress for a similar reason as larger debris has more of a random orientation than grass and other smaller debris. A comparison was also done between areas of the TDS with reflectivity greater than 40 DBZ and less than 40 DBZ. The impact of debris types on the radar couplet is examined by measuring the change of the zero line orientation before and after the tornado encountered buildings and structures. The analysis shows that the radar couplet becomes more divergent after the tornado encounters building and structures suggesting larger debris centrifuging by the tornado.
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