2009 Stream 3 : New features =

Last edited Timestamp?

---

S3.1 : from the community

It is of paramount importance to incorporate features developed in the NEMO community and identified as priorities by the Developer’s Committee in order to improve the system and encourage further developments. The 7 actions are:

S3.1-a — Tidal mixing scheme

Status: zdftmx.F90 added in the trunk and validated in orca2-lim (NEMO-paris), see ticket #425 . It includes both a bottom intensified vertical mixing in areas of internal tide generation (Simmons OM 2005, Bessière PhD 2007) and an intensification throughout the water column in the Indonesian area (Koch-Larrouy et al. 2007, 2008a,b).
Pending issues: on-line comments and minor optimisation (see detail in ticket #457), bug correction in the call (see ticket #462) , and paper documentation #458

S3.1-b — Three bands light penetration + ocean colour

Status: The light penetration developed by Lengaigne et al. (CD07, GRL08) has been introduced in traqsr.F90 in the trunk. It includes an optional coupling to PISCES or the use of ocean color data. It has been validated in orca2-lim-pisces (NEMO-paris), see ticket #428. Note that new namelist parameters have been introduced to control it.
Pending issues: paper documentation, see ticket #459

S3.1-c — Diurnal cycle on solar radiation

Status: Bernie et al. (2007) distribution of the daily solar radiation onto the diurnal cycle has been implemented in an on-line module and validated in orca05 simulation on NEMO v2 by S. Masson and co.
Pending issues: its incorporation in v3. To be done by NEMO-Paris

S3.1-d Conservative Leap-Frog + Asselin filter

Status: ongoing work (NEMO-Paris). See detail 2009WP/2009Stream3/LeapFrogC

S3.1-e — Observations operator code and increments application

Status: on going work (NEMO-Exeter, ECMWF).

S3.1-f — Ice-shelf melting parameterisation

Status: See Wang & Beckmann (AG 2007), PhD of P. Mathiot (2008). To be done by NEMO-Paris. The key issue here is that the existing code does not include the volume flux associated with the ice-shelf melting. A major change have to be performed prior to its incorporation in the reference version.

S3.1-g — Parameterisation of katabatic winds

Status: See PhD of P. Mathiot (2008). to be done by NEMO-Paris.

---

S3.2 : from NEMO team (short-term)

It consists of the short-term developments associated with the priorities of each consortium member that will be incorporated into the system, as they can be useful for the user community. The actions of the 8 sub-stream are:

S3.2-a — New forcing

Tidal potential, atmospheric pressure (NEMO-Toulouse)
River input scheme (NEMO-Exeter)

S3.2-b — Revisit of mass and salt fluxes between ice, ocean and air

Status : on going work (NEMO-Southampton).
As a consequence of the embedding of sea-ice into the ocean (see S3.2-c), the total mass of salt of the combined sea-ice/ocean system is conserved by removing a volume of water from the ocean when ice forms or adding a volume of water when it melts. When ice forms, salt contained in the water is returned to the ocean, less the salt retained in the ice itself. When ice melts, the salt contained is added back to the ocean.

S3.2-c — Embedding sea-ice inside the ocean

Status : on going work (NEMO-Southampton).
To improve the coupling between the sea-ice and ocean models, we embed the sea-ice into the ocean by changing the volume of the ocean and depressing the ocean interface by a depth equal to the mean ice draft. The latter is calculated as the water equivalent of the total ice and snow mass in the model grid box using in-situ local densities of seawater. The pressure gradient that takes into account the total weight of sea ice and snow in the top model grid box is added to the ocean momentum budget. The vertical coordinate is redefined for the whole water column.
The above scheme has been implemented and tested in a 100-year long integration of an ORCA2-LIM2 configuration using both linear and non-linear free surface options. It has also been tested for short runs in the ORCA2-LIM3 configurations. A longer run in ORCA2-LIM3 will take place early in 2010 and the code committed for the NEMO 3.3 release.

S3.2-d — New advection schemes

PPM, Quickest and Prather.

S3.2-e — Lateral ocean physics

Isoneutral operator, skew flux, Visbeck coefficients, slope limitation.

Working prototype code for the iso-neutral and skew-flux operator is under revision and will be ready for the 3.3 release. Considerable care has been taken in the formulation to ensure the tensorial representation is consistent with the variable volume layers (S-coordinate/z* representation). This has been documented and will be provided with the release. Process model studies with this code have been successfully completed. Options for slope limiting have been considered and will be thoroughly tested before release.

Status : on going work (NEMO-Southampton).

Aiki formulation. (NEMO-Paris)

S3.2-f — Ice improvements

momentum forcing, snow-ice formation, EVP rheology in LIM2.

S3.2-g — Improved s-coordinate option

hydrostatic pressure gradient computation, POLCOM-style s-coordinate. (continuation & end)

S3.2-h — Vertical physics

improvements of TKE scheme, addition of a Generic length scale model

--- zdftke2.F90 : validation in global configuration, update of the paper documentation.
Status: zdftke2.F90 has been provided by NEMO-Toulouse, with its paper documentation, and put in release v3.1 (except the doc).
Problems have been found within orca2-lim in both forced and coupled mode (NEMO-paris).
Pending issues:
(1) add the paper documentation in the trunk (DOC).
(2) bug corrections:

correct the prandl number computation in order to avoid a floating point exception, i.e. replace in tke_mlmc routine (see #466):

                  zri = MAX( rn2(ji,jj,jk), 0. ) / (zcoef * (zdku + zdkv + 1.e-20) / avmt(ji,jj,jk)) ! local Richardson number

by

                  zri = MAX( rn2(ji,jj,jk), 0. ) * avmt(ji,jj,jk) / (zcoef * (zdku + zdkv + 1.e-20) )   ! local Richardson number

partial step topography: add in step a missing call to zpshde when zdftke2 is used with ln_dynhpg_imp=FALSE. (see #422)

update avm in all zdf modules so that the shear term in the TKE equation actually corresponds to the kinetic energy lost through vertical mixing of momentum (on going)

(3) change the restart strategy to allow coupled simulation
In the current version, the restart of tke2 requires the computation of en at nitend+1. In coupled mode, the forcing of the next coupled period cannot be known. The restart must be changed from (en , dissl and avt at nitend+1) to (en, dissl, avt, avm, avmu,avmv at nitend) (see #466)

--- zdfgls.F90 : addition of the Generic Length scale scheme (Warner et al. Ocean Modelling, 8, 81-113, 2005).
Status: on-going work (NEMO-Toulouse).

---

S3.3 : from NEMO team (long-term)

It consists of the short-term developments associated with the priorities of each consortium member that will be incorporated into the system, as they can be useful for the user community. The actions of the 8 sub-streams are:

S3.3-a — Revisit of the time stepping in TOP

(2 years, start in 2009)

S3.3-b — Restore the variable volume option (key_vvl)

(2 years, started in 2008)
Status: ongoing work (NEMO-Paris). See detail 2009WP/2009Stream3/VVL

S3.3-c — Towards a generalisation of the split-explicit free surface

(2 years, start in 2009)

S3.3-d — Inclusion of the effect of waves in the marginal ice zone

(2 years, start in 2009)

S3.3-e — Interface to the OASIS 4 coupler

(2-3 years, ongoing, started in 2008)

S3.3-f — AGRIF and sea-ice

(from 0 order to LIM2 and 3 fully AGRIFed) (3 years, started in 2008)
The rheology scheme in LIM is not yet compatible with the AGRIF nesting option when sea ice occurs across the boundary between a nest and its parent. Two approaches are being taken to address this.

1. Switch off the ice model in the nest and use AGRIF code to interpolate the fluxes into the nest.

In this way, the nest feels the presence of sea ice only through the fluxes at the larger scale. This is the "zero order" solution. NOCS has implemented and tested this and it is planned to make it available at the end of 2009 as a separate branch.

2. Fully AGRIF'ed scheme

S3.3-g — Development of TAM

(ANR VODA), with a major contribution from the LJK team (3 years, started in 2008)

S3.3-h — High parallelisation on new platforms

(GPU graphic cards, OpenMP etc …, start in 2009)
(2 years, started in 2008)
Status: ongoing work (NEMO-Paris). See detail 2009WP/2009Stream3/MPP_optimisation

---