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CLIVAR-WGOMD 8 th panel meeting UK Met Office Hadley Centre, Exeter, UK 30April – 01 May 2009

CLIVAR-WGOMD 8 th panel meeting UK Met Office Hadley Centre, Exeter, UK 30April – 01 May 2009. Current status of the Coordinate Ocean-ice Reference Experiments (COREs) in Japan. Hiroyuki Tsujino Meteorological Research Institute / Japan Meteorological Agency collaboration with

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CLIVAR-WGOMD 8 th panel meeting UK Met Office Hadley Centre, Exeter, UK 30April – 01 May 2009

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  1. CLIVAR-WGOMD 8th panel meeting UK Met Office Hadley Centre, Exeter, UK 30April – 01 May 2009 Current status of the Coordinate Ocean-ice Reference Experiments (COREs) in Japan Hiroyuki Tsujino Meteorological Research Institute / Japan Meteorological Agency collaboration with M. Hirabara, H. Nakano, G. Yamanaka, T. Motoi, H.Ishizaki (MRI/JMA) contributions from T. Suzuki, Y. Komuro, Y. Sasaki (JAMSTEC) • Outline: • Some preliminary results from CORE-II related activities in MRI. • Solution / idea to deal with specific questions asked.

  2. Requested issue 1: Summarize use of interannually forced simulations in Japan, and detail experimental design. • Institutional efforts in Japan • Meteorological Research Institute • - CORE-II v2 for 1º x 1/2º global model (used in CMIP5) • - status: on-going • CCSR Univ. of Tokyo / JAMSTEC • - CORE-II v1 for 1/4º x 1/6º global model (used in CMIP5) • - status: done, CORE-II v2 planned • JAMSTEC Earth Simulator Center • - CORE-I for 1/30º x 1/30º North Pacific model, considering CORE-II • - status: highly-likely, CORE-II v2 planned

  3. Meteorological Research Institute CORE-II v2 for 1 x 0.5 CMIP-type global model • Objectives • baseline hindcast simulation of the latter half of 20C to facilitate CMIP5 expt. • to understand interannual variability and trend in the ocean • under “true” atmospheric forcing • Model settings • global (tri-pole) 1º x 0.5º x (L50+BBL) • oceanic component of MRI-CGCM used for CMIP5 • Initialization and integration period (on-going) • initial state: spun-up (accelerated 5000 years and synchronized 500 years) • period: two cycles of de-trended CORE-II ver.2 and one cycle of CORE-II ver.2

  4. Our experimental design and recommendation for CORE-II expt. Requested issue 2: Provide recommendations for CORE-II experimental design. • a.CORE-I-500yr • initial: PHC3.0 (no ice) • forcing: cnyf-v1 • period: 500yrs • purpose: • check with Griffies et al. (2009) • parametersensitivity tests • b. CORE-II-moncl-millennia • initial: “a” or PHC3.0 (no ice) • forcing : monthly climatology of ciaf-v2 • period :50 yrs (synchronous) • ~ 5000 yrs (accelerated) • ~ 500 yrs (synchronous) • terminated when drift becomes small • purpose: • obtain balanced state to initialize “c” • c. CORE-II-20C • initial：”b” • forcing： • 1860-1957 de-trended ciaf-v2 x 2 • 1958-2006 ciaf-v2 • period：1860-2006(-2008) • purpose： • reproduce oceanic state of the latter half of 20C • Notes: • - One of main targets should be long-term trends of the simulated field. • Off-line bio-geochemical model will be run using the flow fields. • There remain concerns regarding discrepancy between re-constructed • (monthly climatology) and original forcing. • Do they really yield similar mean simulated states? • Fresh water flux and salinity restoring adjustment would be needed during the long-term integration. • How should fresh water and salinity restoring adjustments be treated in the interannual run? (Fresh water adj. fixed during integration; salinity adj.) • - This recommendation assumes use of eddy-less models.

  5. A long-term spin-up is needed because • “drift” should desirably be removed from simulated fields to detect “trends” • deep circulation of the Pacific Ocean, which is of particular interest to • Japanese modelers, needs more than a few thousand years to establish Why is monthly climatology used to force the model? - to take a long model time step (e.g., > 6hr; original forcing time interval) - short-time variability in forcing should be absent in a distorted physics How to make CORE-II-monthly climatology and how to calculate fluxes - monthy climatology for all items & scalar wind speed - we presently calculate fluxes in the same way as the 6-hourly data, except - scalar wind speed is based on absolute wind speed - wind stress is calculated using scalar wind speed and relative wind vector High resolution (eddy-permitting/resolving) models might be initialized by a spun-up state of a lower-resolution model and integrated using monthly climatology for 20 yrs, and then switched to CORE-II interannual expt.

  6. Model Settings • Meteorological Research Institute Community Ocean Model • (MRI.COM, Ishikawa et al. 2005) • English document is almost completed and will be released by the end of 2009 • tracer advection scheme： • Second Order Moment (Prather, 1986) for non-accelerated run • UTOPIA and QUICKEST (Leonard 1979, 1993) for accelerated run • - sea ice part: 5-categories, 1-layer ice, EVP dynamics, MPDATA advection • neutral physics: • GM （250 m2s-1 / 100 km x gridsize） and isopycnal diffusion (1000 m2s-1) • viscosity: • Smagorinsky viscosity with scaling factor 4.0, • anisotropic tensor (direction of the flow:1 / normal to the flow 0.2) • SSS restore： 50m / 365day except for coastal gridpoints with sea ice • fresh water flux adjustment: global correction factor for P+R, adjusted annually • tidal mixing parameterization: Kuril Islands (St. Laurent and Simmons 2006) • for the sake of North Pacific intermediate salinity minimum

  7. Test 1. CORE-II-ciaf and CORE-II-moncl as a continuation of CORE-I (500yr) (Note: the model version is changed from the 500th year) CORE-II-moncl: monthly climatology for all items & scalar wind speed Atlantic MOC at 45N Southern Ocean MOC Black: CORE-I Red: CORE-II-moncl (non-accel.) Green: CORE-II-ciaf Drake Passage transports Pacific Deep MOC CORE-II-ciaf and CORE-II-moncl might be expected to yield similar mean fields

  8. Test 2. Long-term (2000yr) accelerated spin-up using CORE-II-moncl forcing Why monthly? … to take a long time step (8hr). Short-time variability in forcing should be absent in a distorted physics Atlantic MOC at 45N Southern Ocean MOC Grey: CORE-I Orange: CORE-II-moncl (non-accel.) Brown: CORE-II-moncl (accelerated) Drake Passage transports Pacific Deep MOC

  9. MOC after 2000 yrs of CORE-II-moncl

  10. Results from CORE-II-ciaf (1): Tropical SST Tropical Indo-Pacific Ocean SST Tropical Indian Ocean SST Anomalies(Yamanaka 2008; GRL) ERA-40 OBS JRA-25 CORE 8July2008 version CORE CORE 5March2009 version OBS(COBE-SST) MODEL CORE-II is superior to reanalyses

  11. Results from CORE-II-ciaf (2): Arctic sea ice annual mean sea ice area 1979-2007 (solid: CORE-II-ciaf simulation, dashed: HadISST) (blue: sea ice extent, red: actual area) correlation： extent:0.81, actual area:0.90 Sea ice seems to have adjusted by 1979.

  12. Shouldn’t CORE-II be extended to the year 2007? upper: HadISST, lower: CORE-II-ciaf simulation extended to 2007 using Japanese re-analysis

  13. JAMSTEC / CCSR Univ. of Tokyo - CORE-II version 1 for 1/4 x 1/6 global model • Objective • check reproducibility of the latter half of 20C • provide physical fields to marine bio-geochemical models • Model setting • global (rotated pole) 1/4 x 1/6 x L50+BBL • oceanic component for the decadal prediction expt. in the context of CMIP5 • Initialization and integration period • initial state: climatological temperature and salinity (WOA01) • period : CORE-II version 1 (1958-2004) 1-cycle • Known problems possibly related to forcing: • low SST along the Equator (too weak radiation?) • thin ice around North Pole (too strong short wave radiation?) • divergent wind-driven ice drift around the Antarctica (too strong wind?)

  14. What are the key scientific uses for interannually forced global ocean-ice simulations? • - to understand ocean’s response (adjustment) to “true” atmospheric forcing • - attribution of recent ocean-climate events to trends or natural variability 2. How does CORE-II fit into the spectrum of coupled climate modelling (e.g., IPCC “historical experiments”) and reanalysis projects such as those addressed in GSOP? - CORE-II could serve as a baseline simulation for 20C expt. of CMIP5 - MRI assimilation group plans a reanalysis expt. using CORE-II in the near future • 3. Can we identify interesting scientific questions that will make a CORE-II project of scientific interest to the panel? • direct comparison with WOCE re-visit observations • detect of trends

  15. 4. What are the baseline metrics required to assess the simulation integrity? • to compare climatological state with WOCE and re-visited WOCE sections • SST, SSH, upper layer heat content 5. What further metrics and diagnostics are of scientific interest for CORE-II simulations? - zonally averaged linear trends of temerature and salinity - some EOFs for SST, SSH, upper layer heat content • 6. What observational datasets and reanalysis products should be used to evaluate the CORE-II simulations? • a carefully QC’ed upper layer temperature data • by Ishii et al.(2006) would be available

  16. 7. Should Large and Yeager (2008), using NCAR bulk formula (as in CORE-I), form the basis of the CORE-II benchmark simulation? What are the problems with this dataset that make certain groups use reanalysis products, or alternative approaches? • “Yes” to the first question • radiation data before 1984 are replaced by satellite climatology • Arctic ice retreat event in 2007 could be a good test for the ocean-ice model 8. Would it be possible to construct key atmospheric forcing fields for the first half of the 20th century and merge this (constructed) forcing with CORE-II to generate a continuous, albeit not fully consistent, data set from year 1900 (or 1880)? - Can objective-analysis SST data by JMA (COBE SST, 1x1, 1890-present) be utilized?

  17. 9. What about the salinity boundary conditions? Should this remain a choice for each group, much as in CORE-I? Can we instead provide more specific guidance, and perhaps make another effort to unify the approaches? • This should remain a choice of each group to guarantee simulation integrity of each group’s model, i.e., to be usable for scientific analyses. • 10. How should the ocean and sea ice models be initialized? What about spin-up time prior to the focused analysis period? What portion of the simulation should be analyzed, and what should be ignored (due to initialization shock)? • simulations are desirably started from a quasi-steady state • if some repeated cycles are applied prior to the last cycle, • the forcing for the cycles except for the last should be de-trended • about first 10 years of the last cycle would not be reliable • sea ice may be feasible after a short period even without careful initialization 11. Are there any un-spoken issues that may handicap the goal of producing a common benchmark simulation (besides the magnitude of the effort)? -

  18. 12. How can we make the CORE-II simulation output more accessible to the broader community? • making use of repository, like PCMDI, REOS would be useful • publish an inter-comparison paper to notify this project to broader community • 13. Is it feasible, and of interest, to aim towards a comparison paper to be written during 2010? • Yes, our CORE-II expt. would be completed by early 2010. • A new set of CORE-II expt. with some specific protocols would be possible. 14. How can we coordinate simulations leading up to a CORE-II paper (e.g., password protected Wiki page monitored by Anna)? - Wiki would be useful. More “on-the-spot” discussion would be needed.

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