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Possible Changes in Tropical Cyclone Frequency andIntensity due to Global Warming
Masato SUGI
Research Institute for Global Change, JAMSTEC
3173-25 Showa-machi, Yokohama, Kanagawa 236-0001, Japane-mail: msugi@jamstec.go.jp

Abstract
This paper reviews assessments of possible changes in tropical cyclone frequency and intensity due toglobal warming, based on climate change projection experiments using atmospheric general circulation
models (AGCMs). Recent experiments with relatively high-resolution (mesh size of about 100 km or less)models consistently indicate that the global frequency of tropical cyclones is likely to decrease due to global
warming. In contrast to the global frequency, the regional tropical cyclone frequencies projected by various
models significantly differ from each other. On the other hand, high-resolution (mesh size of about 50 km orless) models consistently indicate that future tropical cyclone intensity (wind and precipitation) is likely toincrease. As a result, the number of intense tropical cyclones may increase, even if the total number of tropical cyclones decreases. The reduction in tropical cyclone frequency and the increase in tropical cyclone
intensity are likely to be qualitative. However, it should be noted that there are enormous quantitative
uncertainties in these projections of possible changes in tropical cyclone frequency and intensity, particularly among the regional changes. The large uncertainties in the projections of regional changes in tropical
cyclone frequency and intensity make it difficult to use the information effectively in planning measures tomitigate the future wind disaster risk associated with tropical cyclones in particular regions. Reducing theuncertainty in climate change projections, particularly regarding regional changes, is the most demanding
task for climate change research.
Key words: climate change, global warming, hurricane, tropical cyclone, typhoon

1. Introduction
Climate change projection is usually conducted usinga climate model (atmosphere-ocean-coupled model). Asa climate projection calculation needs long-term integration (several tens of years to hundreds of years), relatively low-resolution models are used as compared withnumerical weather predictions. On the other hand, ahigh-resolution model is necessary for simulating amature-stage tropical cyclone with a large pressure
gradient and strong winds near the cyclone center.
Therefore, climate change experiments involving tropical cyclones (projections of changes in frequency andintensity of tropical cyclones) using a climate model
have been difficult. To overcome this difficulty, climatechange projections involving tropical cyclones havebeen usually carried out using a two-tier method. In thefirst tier of the two-tier method, a relatively low-resolution climate model (atmosphere-ocean-coupled model)
is used to project future sea surface temperature (SST)changes. In the second tier, a climate change calculation
is made with a relatively high-resolution AGCM (atmosGlobal Environmental Research
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phere model) using the SSTs projected in the first tier.
The second-tier time integration is performed usuallyfor a limited time period (time-slice method). For example, for a projection of the climate of 100 years ahead, a20-year simulation with the projected SST of the final
20 years of the 100-year period is compared with a
20-year simulation using the present-day SST. In Section 2, we review such experiments conducted so far andsummarize the main results. In section 2.1 we take alook at early studies before the IPCC TAR (Intergovernmental Panel on Climate Change Third Assessment
Report). In sections 2.2 and 2.3, we review studies
referred to in IPCC AR4 (Fourth Assessment Report)
and recent studies published after IPCC AR4, respectively. In Section 3, we discuss the remaining issues, andgive concluding remarks in Section 4.

2. Projections of Tropical Cyclone Frequency
and Intensity
2.1 Studies before IPCC TAR (2001)
The first attempt to assess the possible changes in©2009 AIRIES108

M. SUGI

tropical cyclones associated with global warming was
made by Broccoli and Manabe (1990). They used a
Geophysical Fluid Dynamics Laboratory (GFDL)
AGCM with a mesh size of about 300 km. In theirexperiments, tropical cyclone frequency increased whenclimatological clouds were used, while it decreased
when variable clouds were used. Haarsma et al. (1993)
conducted an experiment using a UK Met Office AGCM
with similar resolution. They found that the number oftropical cyclones would significantly increase under afuture warm-climate scenario. There was strong criticism of these early experiments for the models being toocoarse to simulate tropical cyclones reasonably (Evans,
1992; Lighthill et al., 1994). In the late 1990s, an improved experiment with a higher resolution model
appeared. Bengtsson et al. (1996) used a Max Planck
Institute AGCM with a mesh size of about 120 km. They
showed that the global tropical cyclone frequency would
significantly decrease (by about 30%) due to global
warming (Table 1). This was a rather unexpected result
and the reason for the reduction in frequency was poorly
understood. Critics in the late 1990s complained that theresolutions of GCMs were still too coarse to realisticallysimulate tropical cyclones, and therefore, to assess
possible changes in intensity and frequency of tropical
cyclones (Henderson-Sellers et al., 1998).

also found little change in the maximum wind speed ofsimulated tropical cyclones but a 10% to 20% increasein the precipitation associated with tropical cyclones.
McDonald et al. (2005) reported the results of an experiment using a UK Met Office Hadley Centre AGCM witha mesh size of about 100 km. They found a modest
reduction (by about 6%) in global tropical cyclone
frequency, but a significant increase in regional frequency over the Eastern North Pacific (Table 1).
Oouchi et al. (2006) reported the results of an experiment using a very high resolution (20-km-mesh)
Meteorological Research Institute (MRI)/JMA AGCM.
With the 20-km-mesh model, they could simulate tropical cyclones much more realistically than lower resolution models (Figs. 1 and 2). They found a significant
reduction (by about 30%) in global tropical cyclone frequency and an increase in the frequency over the North
Atlantic (Fig. 2 and Table 1). With the 20-km-meshmodel, Oouchi et al. (2006) showed, for the first timeusing a global model, that the number of intense tropical
cyclones may increase in a future warmer climate, even
if the total global frequency of tropical cyclones
decreases (Fig. 3). Regarding changes in tropical
cyclone intensity, high-resolution regional models havealso shown an increase in intensity. With a highresolution (9-km-mesh) regional model, Knutson and
Tuleya (2004) showed 6% higher maximum surface
wind speeds and about 20% greater near-storm rainfall
when CO2 was doubled. With a 30-km-mesh regionalmodel, Walsh et al. (2004) showed a 56% increase in thenumber of intense storms with maximum wind speed
greater than 30 ms–1 when atmospheric CO2 concentration was tripled.
Regarding changes in tropical cyclone frequency, all
the relatively high-resolution models consistently
showed a reduction in global tropical cyclone frequency
under a future warmer-climate scenario, although somelower-resolution models (Tsutsui, 2004; Bengtsson et al.,2006) showed insignificant increases or decreases. In
contrast to the global frequency, the regional tropical
cyclone frequencies projected by various models differ
significantly from each other. Based on these global andregional model experiments, IPCC (2007) concluded in
the Summary of Policy Makers (SPM) of Assessment
Report of Working Group I:

2.2 Studies referred to in IPCC AR4 (2007)
In the early 2000s, results of experiments using relatively high-resolution models were published. Sugi et al.
(2002) and Yoshimura et al., (2006) reported the resultsof climate projection experiments using the Japan Meteorological Agency (JMA) AGCM with a mesh size of
about 120 km. Sugi et al. (2002) found a significant
decrease (by more than 30%) in the global frequency oftropical cyclones due to global warming, but a significant increase (by about 60%) in the frequency of tropical cyclones in the North Atlantic (Table 1). They foundlittle change in the intensity of simulated tropical
cyclones. Yoshimura et al. (2006) conducted experiments using different SST change distributions (ElNinõ-like pattern and La Ninã-like pattern) and different
convection schemes (Kuo scheme and ArakawaSchubert scheme), and they found a reduction in global
tropical cyclone frequency in all their experiments. They

Table 1 Tropical cyclone frequency change projected by relatively high-resolution AGCM experiments. Thechanges are shown in terms of the ratio of future frequency to present frequency. Statistically significant
increases (decreases) at a 95% confidence level are indicated by red (blue).

Reference
Bengtsson et al.
(1996)
Sugi et al. (2002)
McDonald et al.
(2005)Oouchi et al.
(2006)

Resolution

Ratio(%) of TC frequency Future/Present
N
NW
NE
N
S
S
GlobalIndian Pacific Pacific Atlantic Indian Pacific

120km

63

90

66

79

87

36

49

120km

66

109

34

33

161

43

69

100km

94

142

70

180

75

110

82

20km

70

48

62

66

134

72

57

Possible Changes in Tropical Cyclone

Fig. 1 A typhoon simulated by 20 km-mesh MRI/JMA AGCM. The eye, eyewall
clouds and spiral rainbands are simulated. (from MRI/JMA/AESTO ReseachTeam in Kyo-sei Project (FY2002-2007))Fig. 2 Tropical cyclone tracks from observational data (top), present-day climate experiments (middle), and future climate experiments (bottom). The initial positions oftropical cyclones are marked with “plus” signs. The tracks detected at different seasons of each year are in different colors (blue for January, February, and March; green
for April, May, and June; red for July, August, and September; orange for October,
November, and December). (from Oouchi et al., 2006)

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M. SUGI

number per year

frequency was a robust result but the regional changes
in tropical cyclone frequency varied significantly amongexperiments depending on the projected SST change
distribution.
The implications of recent studies after IPCC AR4
are summarized by the World Meteorological Organization (WMO) Expert Team in a new assessment report(Knutson et al., 2010). Below are the Projection Summaries of the assessment report.

Maximum surface wind speed (m s-1)
Fig. 3 Annual mean global tropical cyclone frequency as afunction of maximum wind speed. The abscissa is thelargest maximum surface wind speed in the lifetime ofeach tropical cyclone. The thick solid line, thin solid line
and dotted line indicate present day simulation, future
simulation and observation, respectively. Statisticallysignificant differences between the future and present
are indicated by open or closed circles. (from Oouchi
et al., 2002)“Based on a range of models, it is likely that future
tropical cyclones (typhoons and hurricanes) will become
more intense, with larger peak wind speeds and moreheavy precipitation associated with ongoing increases oftropical SSTs. There is less confidence in projections ofa global decrease in numbers of tropical cyclones.”
2.3 Studies after IPCC AR4
Several studies using high-resolution models after
IPCC AR4 supported and reinforced the IPCC AR4conclusions on the projections of changes in tropical
cyclone frequency and intensity. Bengtsson et al. (2007)
conducted experiments with 180-km, 60-km and
40-km-mesh models and systematically examined theimpact of the resolution of the model on tropical
cyclone projection experiments. With 60-km and
40-km-mesh models, they showed that the number ofintense tropical cyclones may increase, although thetotal number of tropical cyclones will decrease under afuture warmer-climate scenario. This is consistent withthe results of a 20-km-mesh model experiment by
Oouchi et al. (2006). With a 120-km-mesh atmosphereocean coupled model, Gualdi et al. (2008) showed a
16% (44%) reduction in global tropical cyclone
frequency when atmospheric CO2 concentration was
doubled (quadrupled). With a 50-km-mesh GFDL
AGCM, Zhao et al. (2009) showed a modest reduction(by about 15%) in global tropical cyclone frequency.
They also showed an increase in the number ofrelatively intense tropical cyclones under a warmer
climate scenario. Sugi et al. (2009) examined the resultsof experiments using 20-km and 60-km-mesh MRI/JMA
AGCMs with different SST change distributions. They
found that a reduction in global tropical cyclone

TROPICAL CYCLONE FREQUENCY
It is likely that global mean tropical-cyclonefrequency will either decrease or remain essentiallyunchanged owing to greenhouse warming. Late-twentyfirst-century model projections indicate decreases ranging from −6 to −34% globally. For individual basins,there is much more uncertainty in projections of tropical
cyclone frequency, with changes of up to ±50% or more
projected by various models.
TROPICAL CYCLONE INTENSITY
Some increase in the mean maximum wind speed oftropical cyclones is likely with projected twenty-first
century warming, although increases may not occur in
all tropical regions. Studies based on potential intensity
theory and the higher resolution (<20-km grid) models
project mean global maximum wind speed increases of+2 to +11% (roughly +3 to +21% central pressure fall)
over the twenty-first century.
TROPICAL CYCLONE RAINFALL
Tropical-cyclone-related rainfall rates are likely toincrease with greenhouse warming. The range of projections for the late twenty-first century between existingstudies is +3 to +37%. The percentage increase isapparently quite sensitive to the averaging radiusconsidered, with the larger (smaller) sensitivities reported for the smaller (larger) averaging radii. Typicalprojected changes are about +20% within 100 km of thestorm centre.

3. Discussion
3.1 Resolution
Climate change projection experiments using AGCM
have come under criticism for the resolution of AGCMs
being too coarse to simulate tropical cyclones realistically, and therefore, the projections of tropical cyclone
frequency and intensity changes using AGCMs are said
to be unreliable. However, during the last ten years, as
the resolution of AGCMs has gradually increased, theresults of experiments have tended to reach some levelof consensus, at least qualitatively. Experiments using
models with mesh-sizes of about 100 km or less consistently project a reduction in global tropical cyclone frequency, and experiments with models with mesh-sizesof about 50 km or less consistently show an increase in
the number of intense tropical cyclones. From thisexperience, it seems that AGCMs with mesh-sizes ofPossible Changes in Tropical Cyclone

50 km or less are appropriate for both frequency andintensity change assessment. It should be noted that not
only a high resolution but also a good convection
parameterization scheme is needed to simulate a very
intense mature stage tropical cyclone realistically.
The intensity of simulated tropical cyclones in the
20-km-mesh AGCM in the experiment by Oouchi et al.
(2006) is much weaker than that of observed tropical
cyclones, as shown in Fig. 3. It is likely that this is aproblem in the cumulus parameterization scheme rather
than a problem with resolution. Indeed, more intense
tropical cyclones are simulated in the 20km-mesh
MRI/JMA model with a new convection scheme (amodified version of Tiedtke (1989) scheme). The relative importance of convection scheme and resolution in
the simulation of intense tropical cyclones has not been
investigated systematically and it is an important subjectof future work.
3.2 Effects of atmosphere-ocean coupling
In experiments using AGCMs, we neglect the effectof atmosphere-ocean coupling.
It is known that an intense tropical cyclone decreases
the underlying ocean temperature and this suppresses
further intensification of the tropical cyclone. If weneglect the effect of this atmosphere-ocean coupling, thesimulated tropical cyclones become stronger. Therefore,
AGCM simulation of tropical cyclones is likely to havea bias toward stronger intensity. It should be noted thatthe effect of atmosphere-ocean coupling is large for an
intense mature-stage tropical cyclone, and it is not solarge at the tropical cyclone genesis stage. Therefore,
projection of intensity changes may be affected to someextent by the effect of atmosphere-ocean coupling, but
the projections of frequency changes may not beaffected so much. In addition, AGCMs may have an
opposite bias (of weaker intensity) like MRI/JMA
AGCM due to the cumulus parameterization scheme. In
such a case, the bias of neglecting atmosphere-ocean
coupling may not be apparent. For a quantitative assessment of intensity changes, the bias due to neglecting theeffect of atmosphere-ocean coupling should be evaluated as well as the other model biases.
3.3 Mechanism of the reduction in tropical cyclone
frequency
The summary on tropical cyclone frequency change
projections in the SPM of IPCC AR4 reads, “There isless confidence in projections of a global decrease in
numbers of tropical cyclones.” One of the reasons for“less confidence” may be that the mechanism of the
reduction in global tropical cyclone frequency is poorly
understood. Sugi et al. (2002) and Bengtsson et al.
(2007) argue that a weakening of tropical circulations
due to global warming may be the reason for the reduction in tropical cyclone frequency. The weakening of
tropical circulation means a weakening of the upward
mass flux associated with cumulus convections. The
most important process in the genesis of a tropical

111

cyclone is the development of a system-scale vortex
through convergence of low-level absolute vorticity.
Therefore, a weakening of upward mass flux associatedwith cumulus convections may lead to a weakening of
convergence of low-level vorticity and weakening of thedevelopment of a tropical cyclone-scale vortex. It
should be noted that a weakening of tropical circulation
due to global warming is found in all the climate projection experiments of IPCC AR4, and therefore, it is avery likely to happen under a future warmer climate
scenario (Held & Soden, 2006; Vecchi & Soden, 2007a).
Sugi et al. (2002) showed that the weakening of
tropical circulation is a result of relatively little increasein precipitation compared with a large increase inatmospheric moisture due to global warming. Furthermore, Sugi and Yoshimura (2004) found that the small
increase in precipitation is a result of a reduction inradiative cooling in the atmosphere due to the overlap
effect of long-wave radiation absorption bands of water
vapor and CO2. It is important to note that there are two
effects of CO2 increase. The first effect of an increase inatmospheric CO2 concentration is a surface warming(greenhouse effect), which leads to an increase in atmospheric moisture and precipitation. This effect isrepresented by SST increase in the AGCM experiments.
The second effect of a CO2 increase is a reduction inradiative cooling in the atmosphere due to the overlap
effect, which leads to reduced precipitation (Sugi and
Yoshimura, 2004). It should be noted that the first effectof a CO2 increase leads to an increase in precipitation,
while the second effect leads to a reduction of precipitation. Yoshimura and Sugi (2005) found that the second
effect of a CO2 increase plays an important role in the
reduction in tropical cyclone frequencies.
They found that tropical cyclone frequencies
decrease when CO2 is increased but surface temperature(SST) does not change. On the other hand, tropical
cyclone frequencies do not change much when thesurface temperature (SST) is increased but CO2 does notchange (Fig.4). This indicates that the reason for the
reduction in global tropical cyclone frequencies due toglobal warming is the direct effect of the CO2 increase
on atmospheric radiative cooling rather than an SST
increase.
Changes in SST, however, may play an importantrole in regional changes in tropical cyclone frequency.
Tropical cyclone genesis takes place in regions of active
convection. The distribution of active convection areas
is sensitive to the distribution of SST. Therefore,changes in regional tropical cyclone frequency are sensitive to changes in relative SST distribution. If convective activity in some regions is enhanced in the future,
the tropical cyclone frequency in that region may increase, even if the global total number of tropical
cyclones decreases. Recently, Vecchi and Soden (2007b)
showed that regional changes in tropical cyclone intensity are also sensitive to changes in relative SST
distribution.

112

M. SUGIintensity (wind and precipitation) will increase in the
future due to global warming. Although these projections are likely qualitative, there is considerable quantitative uncertainty in the projected changes in tropical
cyclone frequency and intensity. Particularly, uncertainties in regional changes are large. The large uncertainties in the projections of regional changes in tropical
cyclone frequency and intensity makes it difficult to use
the information effectively in planning measures to mitigate the future wind disaster risk associated with tropical cyclones in particular regions. To reduce the uncertainty in climate change projections, particularly for theregional changes, is the most demanding task for climate change research.

Acknowledgment
Fig. 4 Global tropical cyclone frequency in the experiments withdifferent SSTs and different Atmospheric CO2 concentrations. From experiment COOL1 to CLIM1 and WARM1,
the SST is uniformly increased by 2°C and 4°C with CO2
fixed. From experiment WARM1 to WARM2 andWARM4, CO2 is doubled and quadrupled with SST fixed.
(from Yoshimura & Sugi, 2004)

Figs. 1, 2 and 3 in this paper are quoted from theresults of a 20-km mesh MRI/JMA model simulation
using the Earth Simulator under the Kyo-sei Project,which was supported by MEXT (Ministry of Education
Culture, Sports, Science and Technology).
References

3.4 Detection and attribution issues
In most of the climate change projection experiments
reviewed in Section 2, “a warm future climate scenario”
is the climate when the atmospheric CO2 concentration
is doubled. In some experiments, the climate at the endof the 21st century in the IPCC A1B scenario is used as“a warm future climate”, but this is almost equivalent toa doubled-CO2 climate. The reason we chose a doubled-CO2 climate or the climate projected for the end of
the 21st century as “a warm future climate” rather than amore realistic near-future climate is that we want to detect clearly the signal of anthropogenic global warming
and clearly assess the impact of climate change and givesome warning. Therefore, if we consider a more realistic
future scenario, the impact may not be as large. If someeffective measures are taken to reduce CO2 emissions,then the projected impact of climate change on tropical
cyclones should be much less than that indicated by adoubled-CO2 climate. Also the impact may not be aslarge in the near future, when the CO2 has not yet increased that much. Likewise, it is difficult to detect climate change signals in past observation data on tropical
cyclone frequencies and intensities and attribute it toanthropogenic global warming, because the impact ofanthropogenic global warming in the past has not beenthat large compared with natural climate variability(Knutson et al., 2010).

4. Concluding Remarks
Recent assessments of the possible changes in tropical cyclone frequency and intensity indicate that thefrequency of tropical cyclones will decrease but their

Bengtsson, L., M. Botzet and M. Esch (1996) Will greenhousegas-induced warming over the next 50 years lead to higher frequency and greater intensity of hurricanes? Tellus, 48A, 57-73.
Bengtsson, L., K. Hodges and E. Roeckner (2006) Storm tracks
and climate change. J. Climate, 19: 3518-3543.
Bengtsson, L., K. I. Hodges, M. Esch, N. Keenlyside, L.
Kornblueh, J.-J. Luo and T. Yamagata (2007) How may tropical
cyclones change in a warmer climate? Tellus A, 59: 539-561,
doi: 10.1111/j.1600-0870.2007.00251.x.
Broccoli, A. J. and S. Manabe (1990) Can existing climate models
be used to study anthropogenic changes in tropical cyclone
climate? Geophys. Res. Lett., 17: 1917-1920.
Evans, J. L. (1992) Comment on “Can existing climate models be
used to study anthropogenic changes in tropical cyclone
climate”. Geophys. Res. Let., 19: 1523-1524.
Gualdi, S., E. Scoccimarro and A. Navarra (2008) Changes intropical cyclone activity due to global warming: results from ahigh-resolution coupled general circulation model. J. Climate,
21: 5204-5228.
Haarsma, R. J., J. F. B. Mitchell and C. A. Senior (1993) Tropicaldisturbances in a GCM. Climate Dyn., 8: 247-257.
Held, I. M. and B. J. Soden (2006) Robust responses of thehydrological cycle to global warming. J. Climate, 19: 56865699.
Henderson-Sellers, A., H. Zhang, G. Berz, K. Emanuel, W. Gray,
C. Landsea, G. Holland, J. Lighthill, S-L. Shieh, P. Webster and
K. McGuffie (1998) Tropical cyclones and global climatechange: a post-IPCC assessment. Bull. Amer. Meteor. Soc., 79:
19-38.
IPCC (2007) Climate Change 2007: The Physical Science Basis.
Contribution of Working Group I to the Fourth Assessment
Report of the Intergovernmental Panel on Climate Change,
Cambridge University Press, Cambridge, United Kingdom and
New York, NY, USA, 996 pp.
Knutson, T. R. and R. E. Tuleya (2004) Impact of CO2-induced
warming on simulated hurricane intensity and precipitation:
sensitivity to the choice of climate model and convective
parameterization. J. Climate, 17: 3477-3495.

Possible Changes in Tropical Cyclone
Knutson, T. R., J. McBride, Johnny Chan, K. Emanuel, G.
Holland, C. Landsea, I. Held, J. Kossin, A. K. Srivastava and M.
Sugi (2010) Tropical Cyclones and Climate Change: An
Assessment. Nature Geoscience, DOI: 10.1038/NGEO779
Lighthill, J., G. Holland, W. Gray, C. Landsea, G. Criag, J. Evans,
Y. Kurihara and C. Guard (1994) Global climate change andtropical cyclones. Bull. Amer. Meteor. Soc., 75: 2147-2157.
McDonald, R. E., D. G. Bleaken, D. R. Cresswell, V. D. Pope andC. A. Senior (2005) Tropical storms: representation and diagnosis in climate models and the impacts of climate change. Clim.
Dyn., 25: 19-36, DOI: 10.1007/s00382-004-0491-0.
Oouchi, K., J. Yoshimura, H. Yoshimura, R. Mizuta, S. Kusunoki
and A. Noda (2006) Tropical cyclone climatology in a globalwarming climate as simulated in a 20km-mesh global atmospheric model: frequency and wind intensity analysis. J.
Meteorol. Soc. Japan, 84: 259-276.
Sugi, M., A. Noda and N. Sato (2002) Influence of global warming on tropical cyclone climatology: an experiment with the
JMA global model. J. Meteorol. Soc. Japan, 80: 249-272, DOI:
10.2151/jmsj.80.249.
Sugi, M. and J. Yoshimura (2004) A mechanism of tropical precipitation change due to CO2 increase. J. Clim., 17, 238-243.
Sugi, M., H. Murakami and J. Yoshimura (2009) A Reduction in
Global Tropical Cyclone Frequency due to Global Warming(submitted to SOLA).
Tiedtke, M. (1989) A comprehensive mass flux scheme for cumulus parametrization in large-scale models. Mon. Weather Rev.,
117: 1779-1800
Tsutsui, J. (2002) Implications of anthropogenic climate change
for tropical cyclone activity: a case study with the NCAR
CCM2. J. Meteorol. Soc. Japan, 80: 45-65, doi:10.2151/jmsj.
80.45.
Vecchi, G. A. and B. J. Soden (2007a) Global Warming and the
Weakening of the Tropical Circulation. J. Clim, 20: 4316-4340.
Vecchi, G. A. and B. J. Soden (2007b) Effect of remote sea
surface temperature change on tropical cyclone potential intensity. Nature, 450(7172): 1066-1070.

113

Walsh, K. J. E., K.-C. Nguyen and J. L. McGregor (2004)
Fine-resolution regional climate model simulations of the
impact of climate change on tropical cyclones near Australia.
Clim. Dyn., 22: 47-56, DOI: 10.1007/s00382-003-0362-0.
Yoshimura, J., M. Sugi and A. Noda (2006) Influence of greenhouse warming on tropical cyclone frequency. J. Meteor. Soc.
Japan, 84: 405-428
Zhao, M., I. Held, S.-J. Lin and G. Vecchi (2009) Simulations ofglobal hurricane climatology, interannual variability, andresponse to global warming using a 50-km resolution GCM. J.
Clim, 22: 6653-6678.

Masato SUGI
Dr. Masato Sugi is a Principal Scientist at
Research Institute for Global Change ofJapan Agency for Marine-Earth Scienceand Technology (JAMSTEC). During the
35 years until March 2009, he has beenworking at Japan Meteorological Agency(JMA) and Meteorological ResearchInstitute (MRI). His research area covers
development of numerical weather prediction models and climate models, and climate studies using these models.
Recently his main research interest is the impact of climate change on
tropical cyclones. He is now a member of WMO Expert Team on Climate
Impacts on Tropical Cyclones.

(Received 29 September 2009, Accepted 25 December 2009)