Spatial distribution and frequency of lightning activity and lightning flash density maps for Australia

[1] The spatial distribution and frequency of lightning activity in Australia have been analyzed using lightning data obtained by ground-based lightning detection instruments denoted CIGRE-500 and CGR3 and by NASA satellite-based instruments denoted OTD and LIS. The geographical distribution of lightning incidence is described by a map of total lightning flash density, Nt (i.e., cloud-to-ground and intracloud flashes). A high level of lightning activity, Nt > 10 km−2yr−1, is observed in the northern parts of Australia, and a decrease in total flash density occurs southward to Nt < 5 km−2yr−1 in the central and southern parts of Australia. The peak lightning occurrence is in the northwestern part of the Australian continent with Nt values up to about 35 km−2yr−1 centered around 16°S 126°E. A reduction in Nt by a factor of about 10 for a change in latitude from 10°S to 40°S was found, which is in agreement with the earlier studies. The data from all the sources were used to estimate the cloud flash-to-ground flash ratio, Z, which at the studied localities was found to be in a range of values from 0.75 to 7.7. We concluded that for the range of latitude over Australia the most representative value of Z is about 2 ± 30%, and it is relatively independent of latitude. We used this to develop a map of average annual lightning ground flash density, Ng, the first for Australia. Ng varies from over 6 km−2yr−1 in the northern parts of Australia to about 1 km−2yr−1 and below in the southern parts.