1. 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)

2. 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 into CMIP5 analysis Mean field

3. 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.

4. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 4 / 21 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) Weak point: Relatively coarse horizontal resolution T106 at the utmost. TC intensity is hardly simulated, but its frequency seems to be possible. It is necessary to confirm model performance in simulating TC genesis distribution.

5. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 5 / 21 Objective To analyze CMIP3 archives to assess global warming impact on TC genesis over the western North Pacific.  Evaluation of model performance in simulating the genesis distribution.  Multi-model based projection.

6. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 6 / 21 Models 12 models (among 24 CMIP3 models)  Horizontal resolution of the atmospheric component is T42 (~300 km) or greater.  Daily-mean outputs are archived at the CMIP3 database. Model nameCountryAtmospheric resolution BCCR-BCM2.0NorwayT63 with “reduced” Gaussian grid equivalent to T42 CGCM3.1(T63)CanadaT63 with “reduced” Gaussian grid equivalent to T42 CNRM-CM3.0FranceT63 with “reduced” Gaussian grid equivalent to T42 CSIRO-Mk3.0AustraliaT63 CSIRO-Mk3.5AustraliaT63 ECHAM5/MPI-OMGermanyT63 FGOALS-g1.0China2.8 deg. Lat. × 2.8 deg. Long. GFDL-CM2.0U.S.A.2.0 deg. Lat. × 2.5 deg. Long. GFDL-CM2.1U.S.A.2.0 deg. Lat. × 2.5 deg. Long. INGV-SXGItalyT106 MIROC3.2(hires)JapanT106 MRI-CGCM2.3.2JapanT42

7. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 7 / 21 Definition of TC-like disturbance (1) 850-hPa relative vorticity (  850 ) local maximum (=TC center)   t. (cyclonic vortex) (2) (300-hPa temperature (T 300 ) at the center)  (environmental T 300 )  T t. (warm core) (3) Conditions 1 & 2 are satisfied at least 2 time steps. (4) Genesis point is over the ocean. (5) At genesis time, maximum wind speed is greater at the 850-hPa level than at the 300-hPa level. (exclusion of extra-tropical cyclones) Thresholds (  t, T t ) are determined independently for each model.

8. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 8 / 21 Evaluation of model performance - 20th-century experiment -

9. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 9 / 21 Annual TC genesis (20th-Century experiment) Taylor (2001) diagram 0.6420.780 0.492 0.7400.754 0.409 0.3500.025 0.742 0.0330.678 0.526 [(5  Lat.  5  Lon) -1 (10yrs) -1 ] Yokoi, Takayabu, Chan (2009, Clim. Dyn.) Model simulations Observation T63 with “linear” reduced Gaussian grid T63 T106

10. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 10 / 21 Seasonal march Overall winter-to-summer contrast is well reproduced. i k Observation - High performance models only - 120-150E mean Yokoi, Takayabu, Chan (2009, Clim. Dyn.)

11. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 11 / 21 Monsoon trough May-Jun. Jul.-Sep. Model (example)Observation Tone:  850 Vector: vertical shear Simulated monsoon trough located to the north of the observation.  Biases in TC frequency seasonal march Yokoi, Takayabu, Chan (2009, Clim. Dyn.)

12. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 12 / 21 Seasonal migration of monsoon trough Monsoon trough migrates northward during April–August, and retreats southward during August–December. The trough simulated by five star models migrate northward too fast in early summer, and reaches too north during mature summer. 850-hPa relative vorticity in 120–150  E Observation Yokoi, Takayabu, Chan (2009, Clim. Dyn.)

13. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 13 / 21 Multi-model based projection

14. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 14 / 21 20C3M and SRES We compare the cyclogenesis frequency between 20C3M and average of three SRES experiments.  20C climate simulation (20C3M): 40-yr length.  SRES A1B, A2, and B1 experiments: 80-160-yr length. Model name 20C3MSRESA1BSRESA2SRESB1 TT 1961- 2000 2046- 2065 2081- 2100 2181- 2200 2046- 2065 2081- 2100 2046- 2065 2081- 2100 2181- 2200 CGCM3.1(T63)xxxxxxx3.2 CSIRO-Mk3.0xxxxxxxxx1.9 CSIRO-Mk3.5xxxxxxxx2.9 ECHAM5/MPI-OMxxxxxx2.9 INGV-SXGxxxxx2.9

15. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 15 / 21 Future projection (TC frequency) ALL 5 models project  increase trends over central North Pacific (CNP), and  decrease trends over the South China Sea (SCS) and areas to the north and east of Philippines. 20th-century experiment (5-model ensemble) Projected trends ( [SRES A1B/A2/B1] – [20C3M] ) Yellow （ blue ） tone: all 5 models project increase （ decrease ） trends. Yokoi, Takayabu (2009, J. Meteor. Soc. Japan)

16. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 16 / 21 Comparison with ENSO signals Reasons for the increase trends can be discussed by analogy with El Nino situation. Eastward extension and intensification of monsoon trough is essential. TC genesis anomaly in El Nino years GW impact on SST Yokoi, Takayabu (2009, J. Meteor. Soc. Japan) 850-hPa relative vorticity (JASON) 1982-2001 ENSO signal GW impact

17. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 17 / 21 Yokoi, Takayabu (2009, J. Meteor. Soc. Japan) Decrease trend in and around the South China Sea Environmental conditions would become more favorable for cyclogenesis, or not show significant change.  Low-level vorticity, vertical wind shear, SST, mid-level humidity. Observed interannual variability of cyclogenesis is not correlate significantly with ENSO signals. Projected trends in environmental fields Projected trends in cyclogenesis frequency

18. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 18 / 21 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)

19. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 19 / 21 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. Emanuel and Nolan (2004) genesis potential:  850 : 850-hPa absolute vorticity |u 850 -u 200 |: vertical wind shear V pot : potential intensity (Bister & Emanuel 2002) H 700 : 700-hPa relative humidity Yokoi, Takayabu (2009, J. Meteor. Soc. Japan)

20. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 20 / 21 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.

21. International Workshop on Advancement of Typhoon Track Forecast Technique (Nov. 30-Dec. 2, 2009) 21 / 21 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.