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The southern hemisphere
tropical cyclone (TC) archive consists of cyclone best track data for the TC
seasons from 1969/70 to 1998/99. The creation of a reasonably complete 30-year
dataset for the whole Southern Hemisphere provided the basis for the generation
of a set of climatological data sets showing the frequency of TC occurrence.
A number of quality
control/validation procedures were applied as part of the TC archive generation
process. For example, the data was cross-checked with TC archive data from the
Joint Typhoon Warning Centre, Hawaii, USA. We believe that the 1969/70 to
1998/99 TC archive accurately represents cyclone best track data in the Southern
Hemisphere.
For the 30-year period
corresponding to the 1969/70 to 1998/99 TC seasons, cyclone tracks were analysed
across the southern hemisphere at a resolution of 2° x 2°.
The number of occurrences of cyclones in each 2° x 2°
square was then calculated and the data
converted to two-dimensional gridded format.
The derived gridded
information shows the average annual occurrence of tropical cyclones as well as
the average annual cyclone occurrence during El Niño, La Niña and neutral years.
Note, El Niño and La Niña years were taken from Wright (2001).
The calculation of
cyclone occurrence in this study was similar to the analysis done by Lourensz
(1981) which was based on 5° lat/long squares. However, these gridded data sets
show annual occurrence rather than decadal incidence information, and a finer
rectangular resolution was used in this analysis (2° lat/long
squares).
References
Lourensz, R.S. 1981.
Tropical cyclones in the Australian region July 1909 to June 1980. Australian
Government Publishing Service, Canberra, 94 pp.
Wright, W.J, 2001: A
review of Australian climate in the 20th Century. Preprints, CLI-MANAGE 2000
(Conference on Managing Australian Climate Variability), Albury, NSW, Australia,
Bureau of Meteorology, 127-130. |
