Thursday, 13 February 2003: 3:30 PM
Thunderstorm characterizations derived from cloud to ground lightning flash data based on intercomparisons of Hovm÷ller diagrams and spatial density data
The characterization of thunderstorm behavior over a portion of the Midwest, centered on Kentucky (35-41░ N, 79-92░ W) during spring months, is demonstrated through intercomparisons of Hovm÷ller diagrams and geographical images of cloud-to-ground lightning events. The area includes all of Kentucky as well as major parts of Tennessee, Indiana, Illinois and Ohio. The lightning data are taken from archives of the National Lightning Detection Network (NLDN). The period of interest is from April-June. The Hovm÷ller diagrams consist of time vs. distance plots of lightning activity with the distances being chosen as latitude and longitude. The plots have a spatial resolution of 0.02░ and a temporal resolution of 15 minutes. The geographical images consist of latitude-longitude density plots that represent temporal samples of the lightning events; the spatial resolution of these are 0.05░ in both latitude and longitude.
Generic storm types are readily identified on the geographic images for cross identification on the Hovm÷ller diagrams. The features of these storms and their behavior in time are further revealed through intercomparison of the different representations. Squall lines and individual cells are identified and tracked. Cell merging as well as cell splitting are observed. Essentially, the dual representation of lightning activity provides a very useful tool for characterizing thunderstorm events. Speeds, directions, growth, decay, lifetimes and flash intensities of thunderstorm cells are readily derived from the Hovm÷ller diagrams. Diurnal and other cyclic patterns of thunderstorm activity are also revealed. The results demonstrate the importance of these representations in the nowcasting of thunderstorms and related weather phenomena.