Characteristics of lightning ground flashes in Sri Lanka, in the tropics, were measured by recording the electric field generated by the whole flash at microsecond resolution. The geometric and arithmetic means of the interstroke intervals were 57 ms and 83 ms, respectively. It was found that about 35% of the multiple stroke, negative ground flashes had at least one subsequent stroke with a peak electric field larger than that of the first return stroke. Furthermore, about 12% of the subsequent strokes had peak electric field amplitudes larger than those of the first return strokes. The geometric mean of the subsequent stroke peak field to the first return stroke peak field ratio was 0.44. The mean number of strokes per flash was 4.5, and 21% of the flashes were single-stroke flashes. A comparison of the results with those observed in Florida and in Sweden shows that there are remarkable similarities in the characteristics of lightning ground flashes observed in different geographical regions.

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The position reconstruction of the point of strike of cloud-to-ground lightning flashes in several thunderstorms recorded by two-wideband magnetic direction finding stations is presented. Lightning activity data show a clear peak around 18.00 hours, which is a characteristic feature of the Northeast monsoon thunderstorms in Sri Lanka. It is shown that the accuracy of the position reconstruction with two stations is heavily dependent on the difference in the angles measured by the stations. A technique that utilizes the measured strength of the flashes was introduced to improve the accuracy of the position reconstruction. With this technique, the point of strike of ground flashes can be localized with an accuracy of better than ±5 km within a 100 km radius around Colombo (6.90N, 79.86E), except in the vicinity of the line joining the two stations.

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