"Climate Change and Southern Hemisphere Tropical Cyclones" International Initiative – Progress since the First International Conference on Indian Ocean Tropical Cyclones and Climate Change - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 19

data for the recent TC seasons have been regularly added to the SHTC archive
and it now consists of TC best track data for the “satellite era” i.e. the TC
seasons from 1969-70 to 2009-10, covering name (and/or unique identification
number), position and intensity (in terms of central pressure) (Dowdy and
Kuleshov, 2012).
The availability of satellite imagery has significantly improved our
knowledge of TCs, with satellite remote sensing being vital for accurate
estimates of parameters such as TC intensity and position (e.g. the location of
minimum atmospheric pressure). Satellite images are used by forecasters for
preparing operational and best track data, and a complete digital Geostationary
Meteorological Satellite (GMS) archive for the SH was prepared by the
Australian Bureau of Meteorology for use in TC reanalysis (Broomhall et al.,
2010).
Quality of historical TC data is highly important when analysing trends.
Worldwide the underlying technique for determining TC intensity is the Dvorak
analogue procedure based on patterns of infra-red brightness temperature
(Dvorak, 1984; Velden et al . , 2006). The original version of the technique,
applied to visible satellite imagery, was published in 1975, while its present
form, based on digital infra-red imagery, was published in 1984. It was only
during the mid-1980s that high-resolution multi-channel imagery became
available at the Australian region forecast offices (J. Davidson, pers. comm.).
In addition, supplementary data sources have increased during the past 26 years,
including deployment of automatic weather stations along the Australian
coastline and on small islands, and the advent of satellite-based scatterometer
surface wind estimates. Various authors have discussed the potential impact of
these changes on our ability to accurately determine the intensity of the more
intense TCs in the Australian region, including Trewin (2008) and Harper et al.
(2008). On a global basis, the impact of data quality on our ability to determine
trends has been discussed by Landsea et al. (2006). A further compounding
issue is that during forecast operations, the Dvorak technique output and the
classification of TCs into intensity classes are both based on estimated sustained
wind speeds. Intensity in terms of central pressure is then obtained through a
wind-pressure relationship. Different wind-pressure relationships are in use in
different forecast offices and warning centres across the SH (Knaff and Zehr,
2007; Harper et al., 2008), and there have been changes in the wind-pressure
relationships used through the period of study. The importance of this for
determination of trends is that the SHTC (in its current state) contains only the
derived central pressure information and does not contain the wind-speed
intensity estimates used operationally.
For the western SIO where the tracks are maintained by Météo-France (La
Réunion), operational meteorologists consider the intensity data insufficiently
reliable for trend estimation prior to the establishment of the RSMC La Réunion
in 1993 (P. Caroff, pers. comm.). A further improvement in data quality occurred