Handout (89.6 kB)
Previous studies have developed thunderstorm climatologies using lightning, observed thunder and low resolution radar data. Using observed thunder and lightning data to determine the frequency of thunderstorm occurrence fails to identify individual cells. Using Manually Digitized Radar (MDR) output provides a spatial resolution of 45 km by 45 km
and a temporal resolution of one hour. This resolution is too large to accurately represent individual thunderstorms. These approaches may under represent the true population of thunderstorm occurrence. Studies addressing lightning multiplicity have also shown a fifteen minute cycle in small sample sizes and conclude that larger sample sizes are needed.
The ThOR algorithm is the main tool for this research. ThOR utilizes Level II radar data composited with WDSSII (Warning Decision Support System - Integrated Information). The algorithm identifies individual cells and then determines where those cells will be at the next time step based on the mean winds and previous cell movement. This process repeats until the cells drop below a certain reflectivity threshold or move out of the region of interest. At this point ThOR determines the tracks of individual cells based on the least amount of error in each possible track. Once the track is identified ThOR uses cloud to ground lightning strikes from the National Lightning Detection Network to associate lightning to that track. Lightning must be associated to every cell track to be considered a thunderstorm.
Research is currently underway and results will be presented at the meeting.
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