Methodology:

MSLP fields from the ECMWF ERA-Interim reanalysis [1] were downloaded for the period 1-Jan-1979 to 31-Mar-2019 on a reduced Gaussian N80 (~1.125 degree) grid. These data, interpolated onto a full Gaussian N80 grid, were used to drive the University of Melbourne cyclone tracking software [2] for overlapping 18-month periods. The resulting cyclone tracks were combined (using the cyclone tracks starting from 06Z on 1-Jan in each year to 00Z on 1-Jan of the following year) to create a single global record of cyclone tracks including all tracked cyclones starting from 06Z on 1-Jan-1979 to 00Z on 1-Jan-2019. This data set contains the subset of the global record comprising all cyclones that contain at least one point south of 60°S.

[1] Dee, D.P., Uppala, S.M., Simmons, A.J., Berrisford, P., Poli, P., Kobayashi, S., Andrae, U., Balmaseda, M.A., Balsamo, G., Bauer, P., Bechtold, P., Beljaars, A.C.M., van de Berg, L., Bidlot, J., Bormann, N., Delsol, C., Dragani, R., Fuentes, M., Geer, A.J., Haimberger, L., Healy, S.B., Hersbach, H., Hólm, E.V., Isaksen, L., Kållberg, P., Köhler, M., Matricardi, M., McNally, A.P., Monge-Sanz, B.M., Morcrette, J.-J., Park, B.‐K., Peubey, C., de Rosnay, P., Tavolato, C., Thépaut, J.-N. and Vitart, F. (2011), The ERA-Interim reanalysis: configuration and performance of the data assimilation system. Q.J.R. Meteorol. Soc., 137, 553-597. doi:10.1002/qj.828

[2] Murray, R. J., & Simmonds, I. (1991). A numerical scheme for tracking cyclone centres from digital data. Part I: development and operation of the scheme. Australian Meteorological Magazine, 39, 155-166.

Data quality:

As the cyclone tracking software was run in overlapping 18-month periods, the results were subjected to the following quality checks before being combined:

1. The number of cyclone tracks for each year was checked to ensure that it did not exceed 100,000. This check ensured that the track numbers in the combined record were unique - see the definition of Track under "Data structure and data format".

2. The results were checked to ensure that no cyclone track that started in October of year N-1 continued into year N and that no cyclone track that started in year N continued into March of year N+1. This ensured that no cyclones were truncated by using the cyclone tracks starting from 06Z on 1-Jan in each year to 00Z on 1-Jan of the following year to create the combined data set.

3. The results for successive years were checked to ensure that all cyclone tracks starting between 00Z on 1-Nov of year N and 00Z on 1-Mar of year N+1 were identical between the cyclone tracking software runs for year N and year N+1.

These quality checks were passed successfully in all cases.