Analyzing Tornadic Debris Signatures by Integrating Aerial Imagery and Polarimetric Radar Data in GIS

The historic April 27th tornado outbreak of 2011 produced 62 tornadoes in the state of Alabama, with one of the strongest being the EF-5 Hackleburg-Tanner tornado. The UAH Department of Atmospheric Science and Earth System Science contracted Atlantic Aerial Imagery to fly the track and capture high-resolution swaths of the damage path, as well as the paths for the violent Cullman and Cordova tornadoes. This case study involves detailed analysis of the aerial imagery, including digitizing tree-falls and damage points, and outlining a damage path for the tornado. These analyses are then merged with georeferenced TIFF files (GeoTIFF) of UAH ARMOR radar scans of reflectivity, velocity, correlation coefficient, and spectrum width in order to analyze dual-polarization radar Tornado Debris Signatures (TDSs) associated with the Hackleburg-Tanner tornado. An analysis of TDSs from this tornado allows for the characterization of the effects of debris loading as the tornado passed over different types of terrain. This case study is unique in that some damage in the aerial imagery cannot be attributed to the EF-5 tornado, but rather to multiple tornadoes from the previous morning system of April 27th which overlap with this EF-5 tornado from the afternoon. Additionally, a large gap in damage from Harvest, AL to the Tennessee state line is being investigated to determine the possibility that the Hackleburg-Tanner tornado dissipated before reaching Franklin County TN and a 2nd tornado formed along the same path as the original mesocyclone occluded. The combined analysis of aerial imagery and radar data will provide a detailed picture of how the physical damage and radar signatures correlate and the effects of debris loading over different terrain.