Impact Assessment of Climate Change on Coastal Hazards due to Winter Cyclone around Japan using Large Ensemble Database

2008/2/24 Impact Assessment of Climate Change on Coastal Hazards due to Winter Cyclone around Japan using Large Ensemble Database Junichi Ninomiya Yuya Taka Nobuhito Mori Kanazawa Univ. Kanazawa Univ. Kyoto Univ.

Conclusion and Outline of This Study • Extratropical cycloneʼs track shifts northward and its intensity increases in +4K climate, and high wave event due to extratropical cyclone becomes severe. Outline 1. Introduction 2. Methodology 1. Used dataset (d4PDF) 2. Developed extraction algorism 3. Wave simulation 3. Results 1. Future change of extratropical cyclone 2. Future change of high wave 4. Conclusions

Future Change of Extreme Events • IPCC AR5 • Likely : Increasing intensity of Tropical Cyclones (TC) • Lower confidence : Change of Extratropical Cyclones (ETC) TC Track 2013-2017 ETC Track 2013-2017

Coastal Hazards (High Wave) around Japan • Japan has suffered from high wave due to Tropical Cyclones (TC) and Extratropical Cyclones (ETC), but wave directions due to TC and ETC are different. TC track: 2013-2017 ETC track: 2013-2017

High wave due to ETCs: Yorimawari Wave Strong Wind -> High Wave Hokkaido Feb. 23th, 2008 Feb. 24th Toyama Bay 4200 tons caisson Steep Bath. -> Low WE Diss. Shoaling

Aims of This Study • Reveal future change of ETCs around Japan especially related high wave (Yorimawari wave) disaster. • Evaluate future change of Yorimawari wave.

Methodology: Large Ensemble Database (d4PDF: database for Policy Decision making for Future climate change) Model Exp. Configuration • MRI-AGCM Dx=60km res. • • • MRI-AGCM/NHRCM • 60km to 20km Period: 60yrs Initial perturbation • 100 for historical • 15 for future/SST Forcing • SST and sea ice • COBE2-SST • 6 SSTs from CMIP5 scaled +4K SSTs 15 MRI-CGCM3 15 MPI-ESM-MR 15 MIROC5 15 HadGEM2-AO 15 GFDL-CM3 CCSM4 MRI-NHRCM Dx=20km Dt=1hour 100 100 15 NAT di-trend (6000yrs) Historical (6000yrs) +4K (5400yrs) Mizuta et al.(2017) BAMS

Methodology: Developed ETC Extraction Algorism • Smoothing: Sea Level Pressure (SLP) Extracting • Searching: 1hPa smaller than surrounding cells • Moving Distance: EW±4.5º, NS±3º / step Tracking • Duration: longer than 24 hours • Season: Oct. to April Sorting • Maximum Development Rate: 𝜀 1 𝑝 𝑡 12 𝑝 𝑡 12 sin 60° 𝜀 24 sin 𝜑 𝑡 d4PDF regional data ・534,720 (steps per 60 year) x 100 (90) cases

Methodology: Yorimawari Wave due to ETCs d4PDF U10 SWAN 20 km res. ・More than 24 hours stagnation ・10-year return period intensity Extracted ETCs Present Clim: 17 cases +4K Clim: 22 cases

Results Future Change of ETC around Japan and Yorimawari wave

Future Change of ETC Track The number of ETC under present climate #/year #/year Future change of the number of ETC #/year

ETC Intensity around Japan Relationship between minimum ETC pres. and return period. JRA-55 vs Present -> Upper limit of d4PDF. Present vs +4K -> Climate change makes ETC intensify. Relationship between SST and ETC intensity?

Regional ETC Intensity Annual mean Left: Present, Right: +4K 10-year period Left: Present Right: +4K Annual mean Left: Present, Right: +4K

Methodology: Yorimawari Wave due to ETCs d4PDF U10 SWAN 20 km res. ・More than 24 hours stagnation ・10-year return period intensity Extracted ETCs Present Clim: 17 cases +4K Clim: 22 cases

S.D. of Maximum Significant Wave Height Present 17 cases +4K 22 cases

Future Change of Yorimawari Wave Future change of ensemble mean of maximum wave height Future change of ensemble mean wave period Wave height increases 0.25 ‒ 0.75 m, and wave period increases 0.25 ‒ 0.5 s near Toyama bay. This results show that the risk of Yorimawari wave will increase.

Conclusions • Extratropical cyclones (ETC) were extracted from large ensemble dataset (d4PDF), and analyzed. • ETC track shifts northward. • ETCs passing Pacific Ocean decrease, and ETCs passing Sea of Japan increase. • ETC intensity increases. • ETCʼs Return period shortens • SST distribution may affect ETC track and intensity, but their relationship is unclear. • Wave simulation using d4PDF wind due to 10-year return period ETCs evaluated future change of Yorimawari wave. • Wave height: +0.25 ‒ +0.75 m • Wave period: +0.25 ‒ +0.5 s