Investigations of the accuracy of determinations of thunderstorm location with the VLF atmospherics analyzer of the Heinrich-Hertz-Institut

The paper presents results of a series of tests designed to evaluate the capability of a VLF atmospherics analyzer to detect and locate accurately thunderstorms. The analyzer was located in Berlin, while the storms were chiefly in the Caribbean Sea and Central America. Before the tests were carried out, the average group delay time difference had to be determined along with its seasonal variation. The procedure for determining values for this parameter is described, and some attempts to relate its variation to other variables, such as the air density at 90 km altitude, are mentioned. Out of 33 observed thunderstorms, 10 were located reliably, 10 with restrictions, three were undetected, two were uncertain, and eight were not measured on account of instrumental failure.