Lightning detection with 3-D discrimination of intracloud and cloud-to-ground discharges

A new technique has been developed to operate spatially extended VLF/LF lightning detection networks in a pseudo 3-D mode in order to facilitate discrimination of intra-cloud and cloud-to-ground lightning. Time-of-arrival measurements are carried out with high precision to distinguish VLF/LF-emission regions of lightning discharges in higher altitudes and near ground, respectively. This is accomplished by utilizing deviations of arrival times measured at sensor stations close to lightning events as compared to arrival times expected on the basis of 2-D propagation paths. Successful functioning of the method in networks of common dimensions requires that both signal processing and event time tagging is achieved with an accuracy level of about 1 mus. Results are presented from a new network which has been operating continuously since May 2003 and covers southeast Germany in an area of approximately 300 x 400 km. VLF/LF source emission heights of similar to 5 - 15 km have been identified.