An Analysis of the Lightning Detection Threshold Using Electric Field Mill Data at Cape Canaveral AFS, Florida

The mission of the 45^th Weather Squadron (45th WS) is to “exploit the weather to assure safe access to air and space” for Patrick Air Force Base, Cape Canaveral Air Force Station (CCAFS), and Kennedy Space Center (KSC) in support of various operation. To support that mission the 45th WS hosts a suite of weather detection instruments that include a lightning warning system that consists of an array of 31 electric field mills (EFMS) and a lightning detection and ranging system (Department of the Air Force, 1976). Lightning detection and prediction is important for allowing continued operations at these sites.

Electric field mills in the vicinity of Cape Canaveral continuously record data from 31 separate EFM sites 24 hours a day at a rate of 50 Hz. This produces 4,320,000 lines or recorded data daily for each EFM site, a total of more than 16 billion data points annually for the active thunderstorm season. This study seeks to determine a single EFM reading threshold for lightning onset and a separate single EFM reading threshold for lightning cessation. A logistic regression model for time series data is planned to be used to determine EFM reading thresholds for 15 minutes to 30 minutes before the first total lightning detection and after the last total lightning detection in the vicinity of an EFM in 5-minute increments. Threshold values for the EFM will also be considered from 800 volts/meter to 4000 volts/meter in 200 volts/meter increments for each detection time. There is an inclination from the 45th WS that an EFM threshold for 30 minutes prior to a total lightning detection exists at approximately 2000 volts/meter.