Geographical and seasonal characteristics of the relationship between lightning ground flash density and rainfall within the continent of Australia

摘要

Ground-based observations of annual rainfall and lightning incidence collected over periods ranging from 9 to 22 years at 23 stations around the continent of Australia were used to compute values of 'rain yield', defined as the mass of rain produced per lightning ground flash (units: kg fl~(-1)) over a given area of ground. The rain yield was found to vary considerably with geographical location, season and climatic conditions. Of the 23 stations, 5 were mid-continental and these showed a mean rain yield of 2.64 x 10~8 kg fl~(-1) in contrast to the coastal and near-coastal stations that showed a corresponding mean value of 9.91 x 10~8 kg fl~(-1). The difference was statistically significant at the confidence level of 95%. When the stations were classified according to seasonal climate zones, the winter and winter-dominant rainfall stations showed a rain yield of 1.28 x 10~9 kg fl~(-1) while the summer and summer-dominant rainfall stations showed a significantly lower value of 5.44 x 10~8 kg fl~(-1). Again the difference was statistically significant at the 95% confidence level. Every one of the 23 stations showed mean winter rain yields that were significantly higher than the summer values. These differences are attributed to surface heating which controls such parameters as cloud base height and convective available potential energy in the atmosphere. In terms of the behaviour of the rain yield with geographical, seasonal and climatic conditions, the Australian observations are in good agreement with studies in other parts of the world.