Seasonal and latitudinal variations of lightning ground flash activity in Australia

Lightning, one of the most powerful forces in nature, once was mysterious, magical and feared as the great weapon of the Gods. Ancient Greeks feared lightning as it was believed to be hurled by Zeus, the king of the Gods. For the Vikings, lightning was produced by Thor as his hammer struck an anvil while riding his chariot across the sky. American Indians believed that lightning was caused by bright flashing feathers of a mystical bird, and thunder was created by its flapping wings. From ancient times lightning and thunder were associated with each other even if the explanations for these natural phenomena were far from reality. Scientific study of lightning began with the works of Franklin, Lomonosov and Tesla, and today scientists explain lightning as ‘any and all of the various forms of visible electrical discharge produced by thunderstorms. Thunder is the sound emitted by rapidly expanding gases along the channel of a lightning discharge’ (Glossary of Meteorology 1959). During thunderstorms partial separation of electrical charges within the thundercloud usually results in regions with net negative charge mainly in the lower parts of the thundercloud, and regions with net positive charge mainly in the upper part (MacGorman et al. 1981; Williams 1985). Lightning is an electrical discharge between differently charged regions within the cloud (cloud flash, also referred to in literature as intracloud flash) or between a charged region, nearly always the lower negatively charged region, and earth (cloud-to-ground lightning flash, or simply ground flash). Direct and nearby cloud-to-ground lightning strikes can be hazardous to persons, structures and installations. Lightning can start bushfires, which cause damage to the natural environment, property and life loss. There have been 650 registered fatalities Aust. Met. Mag. 53 (2004) 197-204