.. _omips: Ocean and Sea-Ice ================== BLOM '''' In NorESM2, the ocean component BLOM/iHAMOCC can be either run fully coupled to the other model components, or in ocean carbon-cycle stand alone configuration. The latter setup follows the CMIP6-OMIP protocol (see below) and is driven by atmospheric input data derived from reanalysis products (called *data-atmosphere*, DATM). OMIP-type experiments ^^^^^^^^^^^^^^^^^^^^^ The Ocean Model Intercomparison Project (OMIP; Griffies et al., 2016) is an endorsed project in the CMIP6. OMIP provides a protocol for global ocean/sea-ice models forced by a common prescribed atmospheric forcing, and a protocol for ocean diagnostics to be saved as part of CMIP6. OMIP includes a physical component (Griffies et al., 2016) and a biogeochemistry component (Orr et al. 2017). Prior to OMIP, the framework of the Coordinated Ocean-ice Reference Experiments (CORE) provides ocean and climate modellers with a common protocol for running coupled ocean/sea-ice models with boundary forcing derived from common atmospheric datasets. The CORE forcing dataset was described by Large and Yeager (2004, 2009), which is largely based on the surface-atmospheric fields derived from NCEP/NCAR atmospheric reanalysis . CORE has subsequently evolved into phase 1 of the physical part of OMIP (OMIP-1). The OMIP1/CORE-II experiment forces the ocean through use of the interannually varying atmospheric state of Large and Yeager (2009), along with river runoff data based on Dai et al. (2009). The Large and Yeager (2009) forcing dataset covers the period from 1948 to 2009, and has not been updated since 2009. Thereafter, Tsujino et al. (2018) developed a surface atmospheric dataset based on the Japanese 55-year atmospheric reanalysis (JRA-55; Kobayashi et al., 2015), referred to as JRA55-do, which has been endorsed under the protocol for phase 2 of OMIP (OMIP-2). Currently, JRA55-do covers the period from 1958 to 2018 with planned continuous annual updates. Comparing to CORE-II, the JRA55-do forcing has an increased temporal frequency (from 6 hours to 3 hours), and a refined horizontal resolution (from 1.875° to 0.5625°). The readers are referred to Large and Yeager (2009) and Tsujino et al. (2018) for a detailed description of the CORE-II and JRA55-do forcing, respectively, including the bulk formulae used for computing turbulent fluxes for heat and momentum. An evaluation and comparison of the simulated ocean and sea ice mean states and variability from 11 state-of-the-art global ocean/sea-ice models (including NorESM-BLOM), based on OMIP-1/CORE-II and OMIP-2/JRA55-do, is presented by Tsujino et al. (2020). BLOM OMIP specifics ^^^^^^^^^^^^^^^^^^^ - In the BLOM OMIP simulations, sea surface salinity is restored to monthly climatology with a piston velocity of 50 m per 300 days applied globally for both OMIP-1 and OMIP-2 simulations. The restoring salt flux is normalized so that the global area weighted sum of the restoring flux is zero. - A dimensionless parameter 𝛼=1 is used in the estimation of the near-surface wind correction, e.g. **𝛥𝑈** = **𝑈** \ :sub:`atm`\-𝛼 **𝑈** :sub:`ocn`\, to account for the imprint of the ocean currents on the surface wind stress in an ocean/sea-ice model. The OMIP community has not reached a consensus on the way α should be imposed; for a discussion of α and its values among other OMIP models, refer to Tsujino et al. (2020). - The OMIP-1 and OMIP-2 simulations of BLOM have completed 6 repeating forcing cycles of the forcing periods 1948-2009 and 1958-2018, respectively. - The OMIP-1/CORE-II experiment is documented by Bentsen et al. (2020, *in prep.*), including a comparison to a previous CORE-II experiment simulated by the CMIP5 version of NorESM1. In addition, a number of common global ocean and sea ice metrics simulated by BLOM (including both OMIP-1 and OMIP-2 experiments) is included and evaluated in the multi-model synthesis paper of Tsujino et al. (2020). Creating an OMIP case ^^^^^^^^^^^^^^^^^^^^^ General syntax: :: cd /cime/scripts ./create_newcase --case / --walltime