International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 1 / 21 Satoru YOKOI 1 , Y. N. TAKAYABU 1,2 , J. C. L. CHAN 3 1: CCSR, University of Tokyo, Japan 2: JAMSTEC, Japan, 3: City U. Hong Kong, China Tropical cyclogenesis frequency simulated by CMIP3 climate models and multi-model based future projection International Workshop on Advancement of Typhoon Track Forecast Technique (December 2, 2009)
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International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 1 / 21 Satoru YOKOI 1, Y. N. TAKAYABU 1,2, J. C. L. CHAN.
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International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009)1 / 21
Satoru YOKOI1, Y. N. TAKAYABU1,2, J. C. L. CHAN3
1: CCSR, University of Tokyo, Japan 2: JAMSTEC, Japan, 3: City U. Hong Kong, China
Tropical cyclogenesis frequency simulated by
CMIP3 climate models and multi-model based
future projection
International Workshop on Advancement of Typhoon Track Forecast Technique
(December 2, 2009)
International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009)2 / 21
Our project (S-5-2)
Leader: Prof. Yukari N. Takayabu (CCSR, U. Tokyo)
Organizations: U. Tokyo, MRI, JAMSTEC, Nagoya U., Hokkaido U., & Tsukuba U
Target phenomena:
Heating profile due to tropical convection
Tropical cyclone
Madden-Julian oscillation
Asian monsoon seasonal cycle
Silk road pattern
Pacific-Japan pattern
ENSO
Decadal variability
Evaluations of CMIP3 Model Performances for Various Phenomena in the Atmosphere and Oceans, in the
Present-Day Climate and in Future Projections
Exercise using CMIP3 archive
Rush intoCMIP5 analysis
Mean field
International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009)3 / 21
Introduction
How would global warming impact tropical cyclone (TC) characteristics?(frequency, track, intensity, etc.)
Many researchers discussed
global or ocean-basin scale frequency projection
with the use of their own sophisticated high-resolution GCM.
Most recent studies projected decrease trend of global TC number. (e.g. Sugi et al. 2002; McDonald et al. 2005; Oouchi et al. 2006; Bengtsson et al. 2007)
Multi-model based approach will be essential.
• How about regional trends?
- TCs generated at different places tend to affect different countries.
- Inter-model difference should be serious problem.
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CMIP3 multi-model archive
CMIP3: 3rd phase of Coupled Model Intercomparison Project
Outputs of CGCM experiments designed for IPCC AR4.
Strong point: large number of samples
• 24 CGCMs
• 12 series of experiments (20th-century climate, SRES A1B, A2, and B1, etc.)
• Long-term daily-mean outputs (dozens of years for each experiment)
Observed interannual variability of cyclogenesis is not correlate significantly with ENSO signals.
Projected trends in environmental fieldsProjected trends in
cyclogenesis frequency
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Activity in tropical depression-type disturbances (TDDs)
TDD activity: 3-5-day meridional wind at 850-hPa (Takayabu and Nitta 1993).
An TDD active area is realistically simulated.
The activity would decrease significantly over the SCS and to its southeast.
Observed IAV exhibits similar pattern, implying that weakening trends of TDD activity may play a role in decrease trends in cyclogenesis.
Observation
20C3M
Projected trends
Obs. IAV associated with cyclogenesis over the SCS
Yokoi, Takayabu (2009, J. Meteor. Soc. Japan)
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Projected trends in genesis potential
Models realistically simulate horizontal pattern of GP.
GP does not represent east-west contrast in projected cyclogenesis frequency trends.
GP indices proposed by other papers (e.g. Royer et al. 1998; Caron and Jones 2008) project in the same manner.
20C3M (Contour) & Obs. (shade)
Projected trends
Yellow (pale blue) tones: at least 4 models project increase (decrease) trends.
3
700
3
pot
2
200850
5.1
8505
50
70
V
1.01
110GP
H
uu
Emanuel and Nolan (2004) genesis potential:
850: 850-hPa absolute vorticity
|u850-u200|: vertical wind shear
Vpot: potential intensity (Bister & Emanuel 2002)
H700: 700-hPa relative humidity
Yokoi, Takayabu (2009, J. Meteor. Soc. Japan)
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Summary
Five CMIP3 models realistically simulate horizontal distribution in tropical cyclogenesis over the western North Pacific.
ALL of the five models project increase trends of cyclogenesis over the central North Pacific and decrease trends over the South China Sea and regions east of Philippines.
The former increase trends are primarily attributable to projected eastward extension and intensification of the monsoon trough.
The latter decrease trends are associated with weakening trends in activity of tropical depression-type disturbances.
References:
Yokoi, Takayabu, and Chan (2009, Climate Dynamics, 33, 665–683)
Yokoi, and Takayabu (2009, Journal of the Meteorological Society of Japan, 87, 525-538.
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Future research
Trends in occurrence frequency
Is it completely explained by trends in genesis frequency?
Improvement of genesis potential index to make it applicable to global warming problem.