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 periodsudranging from 9 to 22 years at 23 stations around the continent of Australia were used to computeudvalues of drain yieldT, defined as the mass of rain produced per lightning ground flash (units: kgudf l1) over a given area of ground. The rain yield was found to vary considerably withudgeographical location, season and climatic conditions. Of the 23 stations, 5 were mid-continentaludand these showed a mean rain yield of 2.64108 kg f l1 in contrast to the coastal and nearcoastaludstations that showed a corresponding mean value of 9.91108 kg f l1. The difference wasudstatistically significant at the confidence level of 95%. When the stations were classified accordingudto seasonal climate zones, the winter and winter-dominant rainfall stations showed a rain yield ofud1.28109 kg f l1 while the summer and summer-dominant rainfall stations showed audsignificantly lower value of 5.44108 kg f l1. Again the difference was statistically significantudat the 95% confidence level. Every one of the 23 stations showed mean winter rain yields thatudwere significantly higher than the summer values. These differences are attributed to surfaceudheating which controls such parameters as cloud base height and convective available potentialudenergy in the atmosphere. In terms of the behaviour of the rain yield with geographical, seasonaludand climatic conditions, the Australian observations are in good agreement with studies in otherudparts of the world