TOGA COARE: Oceanic lightning

Abstract

A lightning detection network composed of three direction finders was installed in the western Pacific during TOGA COARE. The results are reported from one direction finder, at Kavieng, Papua New Guinea, for the months of January and February 1993. the latter half of the TOGA COARE 4-month period. Land and ocean sectors were defined. The land-ocean cloud-to-ground lightning ratio for 57 days of data is 8.7. The time between the two highest flash count days is 30-40 days, suggestive of the 30-60-day wave previously identified by Madden and Julian (1972). The highest lightning activity occurs around local midnight for both land and ocean sectors. The peak in activity of cloud-to-ground lightning over the ocean leads the peak in cold cloud area by 3-4 h. A small peak in lightning activity over the land sector occurs around 1500 LST. indicating the influence of the diurnal cycle of heating on convective activity around large tropical islands.