UPDATE FROM THE OCEAN MODEL WORKING GROUP A Blend of Recent Activities and Near-Term Priorities

OBJECTIVES: •Address some long-standing algorithmic shortcomings of the Parallel Ocean Program version 2 (POP2),

•Continue to develop new (or improve existing) subgridscale parameterizations and to investigate causes of model biases,

•Improve / upgrade our eddy-permitting model version, •Path towards considering MPAS-O for use in the next plus one CESM version,

•Continue work in support of ‘decadal’ prediction efforts with CESM.

New Ocean Model Diagnostics Package Dave Brown, Sheri Mickelson, Rob Jacob

GOAL: Provide the community with a completely open-source diagnostics package with an option for dramatically improved performance. • Convert IDL-based code to NCL, • Implement Swift code (a parallel scripting language) to

manage scripts in parallel, i.e., netCDF (nco) operators and plotting done in parallel.

Available to the public.

supported by DOE

Coordinated Ocean – ice Reference Experiments (COREs)

Continue to maintain and update the CORE atmospheric forcing data sets – currently the interannual forcing data sets are available for the 1948-2009 period.

Addressing some POP2 Algorithmic Shortcomings led by LANL

Some algorithmic developments are needed in POP2 to address existing / emerging science applications. For example, given intense interest in sea level rise and incorporation of a land-ice component in CESM, abandoning the virtual salt flux approach to represent the exchange of freshwater between the ocean and other model components is a much-needed model development; more frequent coupling of the ocean – than the current once-a-day coupling – allows for resolution of diurnal cycle and inertial periods. Accordingly, we are undertaking the following developments:

i) implement the z* (or other) vertical coordinate to address the possibility of thin (in comparison to free surface displacements) uppermost layers,

ii) eliminate the virtual salt fluxes (and associated treatment for other tracers such as Carbon) in favor of true freshwater surface fluxes,

iii) modify the time stepping scheme to introduce a conservative Robert filter to facilitate high frequency coupling, i.e., order 1 hr.

Other Ongoing Developments led by NCAR in collaboration with community

•Climate Process Team (CPT) on internal wave mixing,

•CPT on sea-ice heterogeneity and its impacts on oceanic mixing,

•EaSM project on topographic control of the Gulf Stream,

•EaSM project on Modeling Ocean variability and Biogeochemical Cycles (MOBY) – MIT Darwin model is in CESM,

•NOAA WAVEWATCH III model has been incorporated into CESM as a new component,

•Parameterization of land-ocean freshwater exchange (DOE SciDAC),

•ROMS in POP2 for west coast of U.S.; ROMS for coral triangle region.

Going slowly (a.k.a., falling through the cracks):

•Anisotropic GM formulation, •Additional work on Southern Ocean biases

CPT: Internal wave mixing

At NCAR, we have been looking at the climate impacts of the wind-generated near-inertial waves (NIW). We have developed and implemented a new NIW parameterization to incorporate their effects on mixing.

Jochum et al. (2013, J. Climate, submitted)

Zonal-mean boundary layer depth: Control (black) and NIW (red)

Less smoothing More smoothing SST difference with

control (°C)

Control SST minus Observations (°C) • Assess effects of bottom topography on the position of the Gulf Stream

• End goal: develop a parameterization for subgridscale boundary processes

• Efforts at NCAR currently focused on topographic influence

EaSM: Topographic Control of Gulf Stream

Eddy-Permitting Ocean Model led by NCAR

Intended to update the high resolution (0.1° horizontal resolution) ocean model version to reflect recent advances in our understanding of model physics:

• Include new physics, e.g., submesoscale mixing, tidal mixing,

• Revise model set-up and update mapping matrices,

• Increase number of vertical levels to 60 (from 40).

Model for Prediction Across Scales (MPAS-O) Todd Ringler, Mark Petersen, Doug Jacobsen, Mat Maltrud, Phil Jones

Los Alamos National Laboratory

• MPAS is an unstructured grid approach to climate system modeling,

• MPAS supports both quasi-uniform and variable resolution grids using quadrilaterals or triangles,

• MPAS is a software framework that can be used as a single component of climate system models, e.g., atmosphere and ocean,

• MPAS offers the potential to explore regional-scale climate change within the context of global climate system modeling with multiple high-resolution regions permitted.

from Todd Ringler

from Todd Ringler

• First MPAS-O paper has been submitted, • MPAS-O has been incorporated within the CESM framework, • Evaluation / inter-comparison of vertical coordinate options has

started, • Work on mesoscale eddy parameterization is underway.

Work on vertical mixing parameterizations: • Community Ocean Vertical Mixing (CVMix) Parameterization • Joint project between NCAR, LANL, and GFDL

CVMix is a software package that aims to provide transparent, robust, flexible, well-documented, shared Fortran source code for use in parameterizing vertical mixing processes in numerical ocean models. …. CVMix modules are written as kernels designed for use in a variety of Fortran ocean model codes such as MPAS-O, POP, and MOM …. When mature, CVMix modules will be freely distributed to the community using open source methodology.

Work in Support of ‘Decadal’ Prediction Efforts with CESM Led by NCAR (supported by NOAA, DOE, and NSF)

Continue work on ocean data assimilation and fully-coupled data assimilation using the Data Assimilation Research Testbed (DART) framework. CESM + DART framework is working and will be made available to the community. Continue work on both improving our decadal prediction capabilities and advancing our understanding of natural and forced climate variability and the AMOC’s role.