Hail Climatology of Australia based on Lightning and Reanalysis

Due to the highly uneven distribution of population in Australia, reporting of severe convective storms experiences major shortcomings. Relative concentration of storm reports is much greater along the southeast coast of the country where major metropolitan centers such as Brisbane, Sydney, and Melbourne are located. In order to estimate the true severe storm frequency in low population regions, other data sources are used to help fill in the gaps. Previous studies have attempted this with model reanalyses, but these only indicate severe environments, not necessarily actual severe weather. One dataset that provides additional guidance is observed lightning from the Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS). Lightning is an indicator that convection occurred, so alone it is used to build a thunderstorm climatology. The combination of reanalysis-based severe environments with lightning data is then used to create a severe hail climatology based on the period 1998-2013. Storm reports can be considered relatively reliable in recent years for highly populated areas like the major cities, so the results are validated against those locations. Results confirm the area of highest activity along the southeast coast roughly between Sydney and Brisbane. The lightning-reanalysis environment blend shows relatively similar hail activity across this area, which is consistent with the assumption that the population density differences lead to significant underreporting. Comparisons are also made with other similar climatologies for Australia. The combination of reanalysis and lightning may be useful in other parts of the world where severe storm reports are limited by low population density.