Development and Validation of Data Assimilative East Sea Regional Ocean Model Kyung-Il Chang 1 , Young Ho Kim 2 , Gyun-Do Park 1 , Young-Gyu Kim 3 1 Research Institute of Oceanography/School of Earth and Environmental Sciences, Seoul National University 2 Coastal Engineering Research Department, Korea Ocean Research and Development Institute 3 Agency for Defense Development
Contents 1 East Sea & Regional Ocean Model 2 Implementation of 3D-Var 3 Validation of 3D-Var system 4 Future Work : Ensemble Kalman Filter 5 Conclusion
Regional setting: East Sea 52 o 50 o Area: 10 6 km 2 0 1000 2000 3000 Mean depth: ~1700 m 48 o Max. depth: ~ 4000 m 46 o SS 44 o JB: Japan Basin 42 o JB UB: Ulleung Basin TS YB: Yamato Basin 40 o KS: Korea Strait YB 38 o TS: Tsugaru Strait UB SS: Soya Strait 36 o KS 34 o 128 o 130 o 132 o 134 o 136 o 138 o 140 o 142 o
Regional setting: East Sea
Regional setting: Circulation Miniature Ocean - Warm & cold water regions - Subpolar front - Deep water formation - Deep circulation - Double-gyre upper circulation - Mesoscale eddies Courtesy of Dr. J.J. Park
Regional setting: Circulation LCC: Liman Cold Current NKCC: North Korea Cold Current EKWC: East Korean Warm Current NB: Nearshore Branch Naganuma (1977) Senjyu et al. (2005)
Regional setting: Water Masses North Korean Cold Water Tsushima Current Water (Coastal mode of the East Sea Intermediate Water) Deep water masses (< 1ºC)
Ulleung Warm Eddy Regional setting: Eddies
A Miniature Ocean in Change Dissolved Oxygen ( μ M) Potential Temperature ( o C) 0 0.2 0.4 0.6 0.8 200 240 280 320 0 500 1000 Depth (m) 1500 2000 Global ocean 1932 :Uda, 1934 temperature change: 2500 1954 :USSR AOS, 1957 substantial warming 1969 :Sudo, 1986 1979 :Gamoand Horibe, 1983 in the upper 3000m, 1996 :Kim et al., 1999 3000 averaging about 0.037 ° C 2005:CREAMS between 1955 and 1998 3500 Levitus et al. (2005, GRL)
Brief History of International Programs Before 1981 Cooperative Study of the Kuroshio and Adjacent Regions (1 st workshop) (1965-1977) Bilateral Collaboration 1981-1992 (Korea/Tsushima Strait submarine cable voltage measurement) CREAMS (Circulation Research of the East Asian Marginal Seas) 1993-1997 Multi-national, multi-disciplinary collaboration CREAMS II 1998-2002 Japan/East Sea Program (USA/ONR) CREAMS/PICES Program 2005 under PICES (North Pacific Marine Science Organization) EAST-I Program (East Asian Seas Time-series: East/Japan Sea)
EAST( East Asian Seas Time-series) - I • International collaborations Joint surveys along meridional and zonal baselines; material flux measurements across the Korea Strait; joint workshops • Eulerian time-series measurements Volume transport monitoring; HF radar; coastal buoy and Super-Station; Volunteer observing ships; Moored observations • Lagrangian measurements Argo floats; Argos drifters; gliders
Research Tasks (EAST-I) � Establishment of integrated ocean time-series system � Ecosystem structure and variability in response to physical forcing � Air-sea interaction, mixed layer dynamics and ecosystem response � Monitoring and understanding the thermohaline circulation � Carbon cycle and its response to climate change � Role of straits in climate and ecosystem � Physical-biological coupled modeling & future climate projection
Observation Systems in the East/Japan Sea SST (NOAA) Input data SSH 50 (T/P, ERS) Validation data East Sea Regional SSW Ocean Model (ECMWF) Hydrographic Data 45 (CREAMS, JODC, KODC) Surface Current 100 (Surface 200 Drifter) 300 40 400 500 600 APEX 700 800 1000 Real-time 35 Monitoring 1500 Buoy 2000 T/S.. CTD-911 Profiler 140 2500 125 130 135 140 (APEX) 3000 Inflow (Cable Voltage) Temperature (PIES)
Highly-resolved Observation in the UB ONR JES Program: URI, KORDI, KU 16 current meters, 23 pressure-gauge- equipped inverted echo sounders Daily T & dynamic fields between June 1999 and June 2001
Regional setting: Circulation & Variability (UB) Mitchell et al. (2005); mean surface dynamic height
ESROM East Sea Regional Ocean Model (ESROM) Horizontal Domain (127.5 ~ 142.5 ° E, 33.0 ~ 52.0 ° N) Horizontal resolution: 0.06~0.1º(zonal), 0.1º (meridional) Modelling periods: 1993~2002 � Based on GFDL MOM3 MS � Z-coordinate level model 50 � Parallel Processing (MPI) � Hydrostatic and Boussinesq approximations 0 0 5 � Open Boundary Conditions 1000 � Barotropic velocity of inflow and outflow – Estimated S S from the transport estimated by submarine cable 45 � Baroclinic structure of inflow – historical hydrography 2000 2000 3000 � Surface Boundary Conditions Tuman 500 � Heatflux - Calculated from meteorological variables 1000 TS JB by Bulk Formula 3000 40 3000 2000 � Saltflux - Restoring to observed SSS 1000 YR 1000 2000 1000 � Windstress - ECMWF 1000 YB � Features 0 0 2000 0 0 0 2 5 � Explicit free surface UB 1000 � Smagorinsky SGS for momentum 1 0 0 0 500 35 500 � Robert-Marshall Isoneutral SGS for tracers � KPP Vertical SGS Parameterization K S � Partial cell 140 130 135
ESROM Surface Boundary Condition Forced by monthly mean Surface Boundary Conditions and Open Boundary Conditions Heatflux – Bulk Formula Saltflux – Restoring to SSS ( ) τ + 1 τ = γ − S S S = − + + ( ) Q Q Q Q Q surf obs surf net sw sen lat lw (WOA2001) = ρ − θ (a) (b) a ( ) Q C C W T Winter Summer sen a p h 10 a 1 = ρ − Q L C W ( q q ) lat a e E 10 a 1 [ ] ⎧ ⎫ − ⎪ 4 0 . 5 ⎪ T 0 . 39 0 . 05 ( e ) F ( c ) = − εσ a a ⎨ ⎬ Q ( ) ⎪ lw SB ⎪ + θ − 3 ⎩ ⎭ 4 T T a 1 a Large, William G., et. al., 1997, Sensitivity to Surface Forcing and Boundary Layer Mixing in a Global Ocean Model : Annual-Mean Climatology, J. of Phys. Oceano., vol. 27, 2418-2447
ESROM Surface Boundary Condition Windstress (ECMWF) − 8 3 10 dyne / cm (a) (b) Winter Summer 2 dyne / cm 2.0
ESROM Open Boundary Conditions � Radiation condition for the tracers and barotropic velocity ∂ φ ∂ φ ∂ φ + + = C C 0 ∂ ∂ ∂ x y t x y ∂ φ ∂ φ ∂ / x = ( ) ( ) C x ∂ ∂ φ ∂ + ∂ φ ∂ 2 2 2 2 t / / x y ∂ φ ∂ φ ∂ / y = ( ) ( ) C y ∂ ∂ φ ∂ + ∂ φ ∂ 2 2 2 2 t / x / y � Zero-gradient condition across the boundaries for the sea surface elevation � An additional nudging term is added for the influxes ∂ ∂ φ φ ∂ φ ( ) 1 τ = τ > + + = − φ − φ ext if C 0 C C out x ∂ ∂ ∂ τ x y t x y τ = τ = = < and C C 0 if C 0 in x y x � Volume constraint [ ] � � � � dV d ∫∫∫ ∫∫ ∫ = = ⋅ = ⋅ dV u n dS h u n dL dt dt V S L b b Marchesiello, P., McWilliams, J.C., and Shchepetkin, A. (2001) Open boundary conditions for long-term integration of regional oceanic models, ocean modeling , 3: 1-20.
ESROM Open Boundary Conditions 5 Transport (Sv) 4 Inflow (Cable Voltage) 3 2 1 0 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Date (month-year) Volume transport through the Korea Strait by a submarine cable between Pusan and Hamada
3-DVar Theoretical Implementation Weaver and Courtier (2001) � A central task in the development of a statistical data assimilation Estimation of background error covariance � Size of background error covariance matrix : ~5 x 10 11 (x 8 byte) = 4,000 Gbyte - neither estimated completely nor even stored explicitly Modeling B matrix as a sequence of operators. Correlation modeling on the sphere using a generalized diffusion equation
3-DVar Theoretical Implementation � Variational assimilation system with atmospheric models Background error covariance - Correlation functions in terms of a spherical harmonic expansion It is not practical for the ocean due to lateral boundary � Assimilation system with oceanic model Lorenc(1992, 1997) and Parrish et al.(1997) : Recursive grid-point filters (UKMO) Derber and Rosati (1989) : Iterative Laplacian grid-point filter (NCEP) ☺ Very efficient and flexible for geographical variations -_- Limited flexibility in the shape of the correlation function difficult to make anisotropic � Objectives : 3D univariate correlation models numerically efficient and sufficiently general; correlation functions with different shape (not just Gaussian), geographically variable length-scale, horizontal/vertical non-separability, and 3D anisotropy.
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