Characteristics of Thunderstorms That Produce Terrestrial Gamma Ray Flashes

Abstract

Ground-based lightning detection systems geolocated 877 terrestrial gamma ray flashes (TGFs) from a sample of 2,279 TGFs detected with the Fermi Gamma Ray Burst Monitor (GBM). From these accurate geolocations, 24 TGFs are found within the Next Generation Weather Radar (NEXRAD) operational range in the Gulf of Mexico, the Caribbean, and the Pacific near Guam. NEXRAD-enhanced echo-top (EET) data show that these 24 TGFs are consistently adjacent to high-altitude regions of the storms. The high EET values suggest that there is likely a detection–selection effect, in which the gamma rays from lower-altitude TGFs are attenuated by the atmosphere so that such TGFs fall below the detection threshold of current space-based detectors. The vertical integrated liquid density (VILD) values and the volume scan reflectivities Z show that these 24 TGFs originate from storms of a wide range of convective strengths. Convective available potential energy (CAPE) values from reanalysis also vary widely, providing additional evidence of the range of convection in these TGF-producing storms.