meteorologytoday / emom

Intermediate ocean model.

EMOM : Ekman Mixed-layer Ocean Model

This is the ocean model used in the paper

Hsu, T. Y., Primeau, F. W., & Magnusdottir, G. (2022). A Hierarchy of Global Ocean Models Coupled to CESM1.

Abstract from paper

We develop a hierarchy of simplified ocean models for coupled ocean, atmosphere, and sea ice climate simulations using the Community Earth System Model version 1 (CESM1). The hierarchy has four members: a slab ocean model, a mixed-layer model with entrainment and detrainment, an Ekman mixed-layer model, and an ocean general circulation model (OGCM). Flux corrections of heat and salt are applied to the simplified models ensuring that all hierarchy members have the same climatology. We diagnose the needed flux corrections from auxiliary simulations in which we restore the temperature and salinity to the daily climatology obtained from a target CESM1 simulation. The resulting 3-dimensional corrections contain the interannual variability fluxes that maintain the correct vertical gradients of temperature and salinity in the tropics. We find that the inclusion of mixed-layer entrainment and Ekman flow produces sea surface temperature and surface air temperature fields whose means and variances are progressively more similar to those produced by the target CESM1 simulation.

We illustrate the application of the hierarchy to the problem of understanding the response of the climate system to the loss of Arctic sea ice. We find that the shifts in the positions of the mid-latitude westerly jet and of the Inter-tropical Convergence Zone (ITCZ) in response to sea-ice loss depend critically on upper ocean processes. Specifically, heat uptake associated with the mixed-layer entrainment influences the shift in the westerly jet and ITCZ. Moreover, the shift of ITCZ is sensitive to the form of Ekman flow parameterization.

Setup

Requirement

• Julia language with packages: NCDatasets, MPI
• MPI interface. In particular, mpiexec is required.

Tutorial

The tutorial, including deriving the flux correction to running the hierarchy, is documented here.

TODO list

• (Done, May 28) make_init to generate initial ocean profile.
• Flux correction procedure.
• Test out energy conservation. Use the "area" variable provided in the domain file to compute the energy flux.
• Test out coupling with CESM1-CAM5
• Test out coupling with CESM2-CAM5