Mechanism of the Indian Ocean Tropical Cyclone Frequency Changes due to Global Warming - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 42

On the other hand, the difference between USSTA run and CO 2 F run indicates
the uniform SST effect, while the difference between F run and USSTA run
indicates the non-uniform SST effect.
4. Global TC Frequency Changes
Main results of this study are reported in Sugi et al. (2012). The global TC
frequency changes are summarized in Fig. 2. The global TC frequency in F
run is 24% less than that of P run. The CO 2 effect evaluated by the difference
between CO 2 F run and P run (F run and SSTF run) is 5.6% (9.8%) reduction of
TC frequency, while SST effect evaluated by the difference between F run and
CO 2 F run (SSTF run and P run) is 19.3% (15.6%) reduction. These results are
basically consistent with previous studies (Yoshimura and Sugi, 2005; Held
and Zhao, 2011), although the CO 2 effect is relatively less than the previous
studies probably due to the effect of other GHGs included in the present study.
Figure 2 indicates that the uniform SSTA effect is a significant reduction of
global TC frequency (18.7% reduction), while the non-uniform SSTA effect
does not change the global TC frequency.
Fig. 2: TC frequency changes.
5. Regional TC Frequency Changes
The regional TC frequency changes are summarized in Fig. 3. The CO 2 effect,
SST effect and total effect (CO 2 effect + SST effect) on regional TC frequencies
are shown in Figs 3a, 3b and 3c, respectively. Figure 3c indicates that the total
effect is an overall reduction of TC frequency in most regions. However, in
Fig. 3c we can see a significant increase of TC frequency in central North
Pacific and western part of the South Indian Ocean. These TC frequency
increases are mainly due to the SST effect as shown in Fig. 3b. In Fig. 3a, we
can see a significant TC frequency increase due to CO 2 effect in north-western