The distribution of thunderstorm days, lightning discharges, and the incidence of lightning discharge derived from VLF sferics data

Distributions were developed for 1972 in the Eastern Hemisphere of thunderstorm days (January, April, July, and October), the incidence of lightning discharge (January and April), and the areal concentration of lightning discharge (yearly). These analyses were based on a review of sferics data. Charts of thunderstorm days differed significantly from mean charts of the World Meteorological Organization (WMO), especially over the oceans, North Africa, Arabia, the Mediterranean Sea, and Southeast China. These areas of sparse data in the WMO compilation have been covered in this investigation. The tentative, first estimate of the distribution of lightning discharges over a large area of Earth differed significantly from the distribution of thunderstorm days for April and July, but the two distributions were similar for January and October. Centers of relatively high occurrence of lightning discharge on a yearly basis were located over South Africa, the Mediterranean Sea, Arabia, Southeast China, Southeast Asia, and Australia. The occurrence of lightning discharge was shown to follow Sun northward from January to the maximum poleward thrust in July. The occurrence of lightning discharge receded equatorward from July to the end of fall in December. The most reliable planetary-scale estimate of the average incidence of lightning discharge was 0.000042 per km per sec for the Northern Hemisphere (0-179E) in January 1972 and 0.000030 per km per sec for April 1972.