A Study on the First Return Stroke in a Thunderstorm Cell

We have classified the first return stroke (RSlst) in a thunderstorm cell using the data recorded by a low-frequency mapping system called Fast Antenna Lightning Mapping Array (FALMA). It is found that the cloud-to-ground (CG) flashes in the cell can be apparently grouped into typical CG, hybrid CG, and CG without apparent PB processes. The majority (61/82) of RSlst are located in the area with the combined reflectivity larger than 30 dBZ. The RS1st in typical CG and in hybrid CG have nearly the same average intensities (5,900 versus. 5,700 DU), both are surprisingly smaller than that for the RS1st without PB processes (7,990 DU). The other properties, involving lightning initiation height, radar echo features, and the horizontal distance between the lightning initiation and RS1st, also have obvious differences among three types of CG flashes. In order to give explanations for such differences, we suggest that it should be deserved to further study the thunderstorm structure and charge regions in the future.