Lightning Climatology of the Lake Victoria Basin in East Africa

Severe nocturnal thunderstorms over Lake Victoria in East Africa pose a significant threat to the local population, reportedly causing several thousand fatalities in the fishing industry each year. Since late 2014, Earth Networks has placed over 15 lightning sensors around the lake, permitting continuous observations of total lightning activity with high detection efficiency. Total lightning occurrence in this region has also been observed during overpasses by Lightning Imaging Sensor (LIS) aboard the Tropical Rainfall Measuring Mission satellite (TRMM-LIS; 1998-2015) and the International Space Station (ISS-LIS; 2017-present). While TRMM-LIS lightning detection was sporadic near the end of the satellite’s lifetime, the launch of ISS-LIS permits extensive, direct comparison of the occurrence and characteristics of lightning over Lake Victoria from satellite and ground-based sensors.

The Earth Networks Global Lightning Network (ENGLN) stroke data in the Lake Victoria Basin are clustered into individual thunderstorms, permitting analysis of preferred genesis locations over the mountains northeast and east of Lake Victoria and evolution of storms as they move over the lake. In addition, seasonal and diurnal lightning variability are examined using four years of data from the ENGLN and a high-resolution TRMM-LIS climatology from Albrecht et al. (2017) in preparation for a 2019 mini field campaign to learn more about the fundamental causation and predictability of these storms. Annual migration of the ITCZ produces a semi-annual cycle in lightning occurrence over the lake, with ENGLN reporting a primary peak of ~400 strokes day^-1 during March-April and a secondary peak of ~300 strokes day^-1 during September-October. Daytime heating of the land surface and convergence of the associated sea breezes produce an afternoon lightning maximum over the terrain surrounding the lake. Thunderstorms frequently propagate southwestward over the lake at night, producing peak lightning density of ~35 strokes per hour at 06 LT.