# Presentation: 190586

## OM1 – Can we apply MOM4 development to BGC?

- OMDT 10/29/03

## BGC code development

**Now available!**
**OCMIP2 Biotic**
**Restoring diagnostic biology**
**Prognostic biology **
**OCMIP2 CFCs**
**Hadley center biology**
**Ongoing:**
**OM1 PRINCE2 forcing (Simeon)**
**OCMIP2 Abiotic and ****14****C (Slater)**
**Field manager (Slater/Cooke)**
**Moving gas exchange to coupler (???)**
**Biological tuning (Dunne)**

## Central Question

**In studying ocean biogeochemistry, the physics is assumed to be “perfect”.**
**None of the MOM4 suite have been validated with geochemical water-mass tracers.**
**While OM2/OM3 may turn out to be “perfect”, they are too slow for development.**
**Conversion of MOM3 to OM1 is ongoing.**
**Will the converted OM1 be sufficient for Earth System Model development?**

## Physical Goals of Model Resolution

**Thermocline**
**Thermohaline circulation **
**Mean currents**
**Current variability (El Nino, TIW)**
**Eddy permitting**
**Eddy resolving**

**OM1**

**OM2 /OM3**

## Problems with OM1 (MOM3)

**Makeshift deep water formation in southern ocean**
**NADW not at right depth**
**NPIW formed from subtropical waters**
**Which forcing/configuration is best?**
**Does not resolve euphotic zone (plants need light)**
**Limited mixed layer dynamics**
**Coarse resolution in the equatorial zone (N-trapping, weak undercurrent, large T errors)**
**No ice dynamics**
**Can’t couple to an Atmospheric Model**
**Physics has not been tuned for MOM4**

## Legacy from MOM3

**Grid inherited from R15 coupled model**
**96 zonal bins to equal atmospheric model**
**Depth scaling doubled from 12 level model**
**Deepest depth to 5000m (OM2/OM3 are 5500m)**
**2 empty rows in Antarctica (40 total)**
***MOM4 grid generation/coupling removes these obstacles***
**Conversion from MOM3 to MOM4 is not exact**
**Free surface rather than rigid lid means time-varying solutions differ  (significantly?)**
**Smaller time step necessary for free surface.  C*****an we make use of this time to do better physics?***
**Tripolar enhancement is there.*****  Does the current grid configuration make best use of it to resolve arctic?***
***Can we apply MOM4 improvements?***

## Proposed Model

**Coarse enough to do many/long runs while capturing important features such as:**
**Euphotic zone**
**Mixed layer dynamics**
**Equatorial undercurrent/recirculation cells**
**Ice**
**Comparable to NCAR/CCSM coupled paleo-model (100x116x25; POP; shifted pole; high res. tropics)**
**Potential for coupling to atmosphere for Earth System Model development**

## Slide 8

|  | MOM3 | OM1 | Proposed OM1 |
| --- | --- | --- | --- |
| Zonal res. | 3.75° (n=96) | 3.75° (n=96) | 3.0° (n=120) |
| Merid res. | 4.5° (n=40) | 4.5° (n=40) | 3.0°-0.6° at Eq (n=64) |
| Vert. res. | 25m to 5000m (n=24) | 25m to 5000m (n=24) | 10m to 5500m (n=28) |
| Partial Cells | No | No | Yes |
| Surface | rigid lid | free surface | free surface |
| t | 24 hours | 12 hours | 3 hours |
| Forcing | NCEP/DaSilva | NCEP/DaSilva | ??? |
| Forcing t | Monthly | Monthly | Daily |
| KH | Constant | Constant | Anisotropic |
| Mixed layer | Constant 50m | Constant 50m | KPP |
| Ice | No | No | Yes |
| Atmos | No | No | ??? |
| rela to OM2 |  | ~200 times faster | 22 times faster |
| diag timing | 50 yrs/day on 1pe | 120 yrs/day on 12pe | 35 yrs/day on 32 pe |
| prog timing | 8 yrs/day on 1pe | 17 yrs/day on 12pe | 19 yrs/day on 32 pe |

## Grids

## Cell area

## Slide 11

## U at 140W

## U along the equator