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.

Two lightning locating systems were utilised in obtaining the cloud-to-ground flash characteristics in Sri Lanka and in the surrounding area of the Indian Ocean. Over 5,000 flashes were recorded during the year 1999 covering 39 thunder days. The lightning data are presented in terms of polarity, multiplicity, and first return stroke peak current. The percentage of positive flashes observed in this study is fairly lower than that of temporal regions but when compared with similar studies in tropical regions there is no clear difference. Out of the 3% of the positive flashes reported, 95% were single stroke. On the contrary only 56% of the reported negative flashes were single stroke. The highest percentage of single stroke negative flashes was 74% in June and lowest was 38% in February. The monthly variation of the percentage of positive flashes ranged from 17% in June to 1% in September. The highest monthly average multiplicity of negative flashes of 2.6 was recorded in February and for all other months it was below 2. The monthly averages of the negative first stroke peak currents ranged from about 39kA in August to about 56kA in September.

Activity of cloud-to-ground lightning flashes observed during the monsoon thunderstorms over Sri Lanka with a lightning locating system consisting of two direction finders (DF) is presented. The Northeast monsoon produced over 884 cloud-to-ground flashes with a peak lightning rate of 96 flashes per hour whereas Southwest monsoon produced 3,294 flashes with a peak rate of 104 flashes per hour. A relative flash density maximum of 198 flashes per 28×28 km 2 was observed over Ratnapura area (6.68N, 80.40E). The percentage of positive flashes and average peak lightning current values for negative flashes are found to be 6.4% and 36 kA respectively for the Northeast monsoon period and 1.7% and 40 kA respectively for the Southwest monsoon period for the flashes that struck within 10-250 km range. No significant difference in average peak lightning current values were observed for the negative and positive flashes in both monsoons.