Characteristics of Global Lightning Activities Based on Satellite Observations

The characteristics of global lightning activities are investigated by using the lightning data recorded by the Optical Transient Detector (OTD) and the Lightning Imaging Sensor (LIS) during 1995-2006. Results indicate that approximately 46.2 fl s^-1 (fl denotes flash and numbers the times lightnings happen) lightning flashes including intra-cloud and cloud-to-ground types occur worldwide and that nearly 78.1% of global lightning flashes occur in the region of 30°S-30°N. Moreover, the lightning density ratio of land to ocean is approximated at 9.64:1. Although offshore areas account for nearly 30% of all oceans, lightning flashes over these areas account for nearly 70% of the total lightning flashes over all oceans; the lightning density over open sea is very low. Furthermore, monthly variations in lightning activities over both land and offshore areas clearly show a characteristic single peak with the maximum appearing in July. The lightning density over offshore areas on the east coast of content is larger than that on the west coast in middle- and high-latitude regions, while the reverse is true over equatorial areas. Variation in lightning density with altitude is represented by two peaks and three valleys with the former appearing at 100-2400 m and 3300-4600 m, and the latter appearing below 100 m, at 2400-3300 m, and above 4600 m. These features are caused by the combined action of various factors influenced by terrain and geographic location.