Negative cloud-to-ground lightning flashes in Malaysia

• We present the statistical characteristics of a large number of negative cloud-to-ground lightning flashes from Johor, Malaysia.
• This is the first time the electromagnetic fields generated by the whole flash are recorded in proximity to the equator (1°N, 103°W).
• This information is important in reducing variations in results due to differing measurement methods and sampling techniques as used by different investigators.
• The results in Malaysia, Florida, Sweden, Sri Lanka and Brazil showed similarity in all characteristics presented in Section 3.

The characteristics of the negative cloud-to-ground lightning flashes in Malaysia are studied by analyzing the electric fields generated by the whole flash in nanosecond resolution. A total of 405 strokes obtained from 100 successive negative cloud-to-ground lightning flashes were analyzed, which were recorded from seven convective thunderstorms during the southwest monsoon period, i.e. from April to June 2009. It was found that the total number of interstroke intervals has an arithmetic mean value of 86 ms, a geometric mean value of 67 ms and does not depend on the return stroke order. Of the 100 negative ground flashes, 38 flashes (38%) have at least one subsequent return-stroke (SRS) whose electric field peak was greater than that of the first return-stroke (RS). Furthermore, 58 (19%) out of 305 SRS have electric field peak larger than those of the first RS. The arithmetic and geometric mean ratio between the peak electric field of the SRS and the peak electric field of the first RS are 0.7 and 0.6, respectively. The percentage of single-stroke flashes was 16% while the mean number of strokes per flash and maximum number of stroke per flash were 4 and 14, respectively.