Development of an Interferometer-type Lightning Mapping Array System

We have developed an interferometer-type of lightning mapping array system for observing 3D lightning discharge progressions in high temporal and spatial resolution. The system consists of three GPS-synchronized interferometers separated at a distance of several kilometers and roughly formed an isosceles triangle. All three interferometers have an identical frequency response from about 1 MHz to 400 MHz. Using this system, we have recorded several winter lightning discharges which are suitable for analysis. In this paper, we have performed an analysis on an example data. First we have analyzed how different frequency bands affect the mapping result. It was found that the mapping results exhibit differences in terms of leader progression continuity and channel width. As a whole, the system worked as expected. In addition, the 3D progression feature of an interesting downward fast negative stepped leader was presented. For an upward leader initiated from a windmill, we have compared the mapping result with the corresponding pictures recorded by a high speed video camera. It was confirmed that the system can be used to detect the progression of upward leaders initiated from tall structures at an acceptable accuracy.