Daile Zhang, Kenneth L. Cummins
Department of Hydrology and Atmospheric Sciences, The University of Arizona, Tucson, Arizona
Lightning has been observed by a ground-based network called the National Lightning Detection Network (NLDN) that was developed over three decades ago within the ATMO Dept. at the University of Arizona. This network, based on electromagnetic wave discrimination in the very low frequency band, has been carefully calibrated and is used in a wide variety of applications across the United States. NASA’s satellite-based optical Lightning Imaging Sensor (LIS) detects lightning in different ways than the NLDN. Comparison of the two sensors requires matching in time and space so that future mapping of lightning from satellites can benefit from past ground- and satellite-based sensors.
In this study, a cross-validation between the NLDN and LIS was examined. The main results show that in time, the LIS discharges were normally reported about 2 ms later than the correlated NLDN discharges. A spatial matching found a roughly 5-km location shift/offset of the LIS-reported discharges relative to the correlated NLDN discharges, which is due to the regular TRMM satellite yaw maneuvers.
A further examination of the LIS-reported illumination areas of the optical signals from lightning discharges were conducted within the NLDN detection domain. It shows that those discharges with large illumination areas have a preference of being positively charged. Positive charges typically are more intense and damaging if they touch the ground than their negative counterparts.
In addition, initial comparison with the ground-based lightning mapping systems indicates that the satellite observations can spatially map horizontally extensive lightning flashes that occur frequently in mature storms, and reflect very large regions of moisture transport into the upper troposphere.