# Presentation: 845578

## Simulation Experiments for Pacific Upwelling and Mixing Physics Study

- Renellys C. Perez
*NRC Postdoctoral Research Associate*
- William S. Kessler
*NOAA/PMEL *
- Paul S. Schopf
*George Mason University*

- NRC Presentation

- 08/01/06

## Goals of PUMP study

- Observe
- processes that control SST in the cold tongue
- evolution of near-equatorial meridional circulation cell
- Improve
- vertical exchange processes in OGCMs
- ability to model coupled climate system

- Mean circulation at 140°W in the MOM2 model. (Courtesy G. Vecchi)

## Goals of PUMP study

- Observe
- processes that control SST in the cold tongue
- evolution of near-equatorial meridional circulation cell
- Improve
- vertical exchange processes in OGCMs
- ability to model coupled climate system

- Mean circulation at 140°W in the MOM2 model. (Courtesy G. Vecchi)

## PUMP moored array

- Two-year array (17 double-buoy pairs):
- cross-equatorial temperature and velocity (u,v) measurements
- surface circulation from near-surface current measurements
- microstructure from near-surface rapid-response thermistors

- Buoy Pair:
- TAO ATLAS (surface) + subsurface upward-looking ADCP mooring
- (from PUMP SIP)

## PUMP moored array

- Two-year array (17 double-buoy pairs):
- cross-equatorial temperature and velocity (u,v) measurements
- surface circulation from near-surface current measurements
- microstructure from near-surface rapid-response thermistors

- “Continuity”
- If flux into diamond is smaller (larger) than flux out of diamond,
- upwelling (downwelling)

## Simulation Experiments for PUMP

- Provide guidance for PUMP array design
- Estimate temporal and spatial scales of (u, v, T)
- Determine representativeness of w, heat and momentum budgets at diamond centers
- Suggest modifications to proposed array
- Study spin-up of 3-d cold tongue circulation in response to varying winds, remotely forced waves, and TIWs
- Vertical structure of poleward divergence
- Transition to Ekman dynamics
- Meridional structure of the zonal currents

## Models and approach

- Models used to study near-equatorial scales of variability and tell us how to best sample the meridional circulation:
- Poseidon Model (Schopf and Loughe 1995)
- reduced-gravity model
- 20 layers
- 5/8o x 1/3o (uniform)
- Modular Ocean Model (MOM4; Griffies et al. 2004)
- z-level model
- 49 levels
- 5/8o x 1/3o (stretches to 1o at 40o latitude)

## Models and approach

- Simulation experiments
- Spin-up the models with climatological forcing
- Vary the wind stress forcing during different phases of the seasonal cycle
- local east/west anomalies
- remotely forced anomalies (westerly wind bursts, Kelvin wave)
- Study
- spin-up time scales
- spatial decorrelation scales of (u, v, T) and horizontal gradients
- vertical structure of diverging meridional circulation and w
- heat and momentum budgets
- representativeness of proposed PUMP array

## Poseidon seasonal cycle results

- Zonal decorrelation scale along 140W: u

## Poseidon seasonal cycle results

- Meridional decorrelation scale along 140W: v

## Poseidon seasonal cycle results

- Annual mean along 140W: v

## Poseidon seasonal cycle results

- Standard deviation along 140W: v

## Poseidon seasonal cycle results

- 09/20 TIW snapshot along 140W: v

## Poseidon seasonal cycle results

- 10/02 TIW snapshot along 140W: v

## Importance of gradients

- Calculation of w from continuity from MOM4 test run

## Importance of gradients

- Calculation of w from continuity from MOM4 test run

## Importance of gradients

- Calculation of w from continuity from MOM4 test run

## What’s next?

- Spin-up MOM4 with climatological forcing
- Compare MOM4 and Poseidon
- Seasonal cycle, TIWs
- Transition to Ekman dynamics
- Structure of meridional circulation
- Sampled seasonal cycle vs. “true” seasonal cycle
- Drive the models with wind stress anomalies and the examine the spin-up of the 3-d circulation

## PUMP moored array and IOPs

- Two IOPs during two-year period
- microstructure and mixing measurements along equator, 2 N
- synoptic cross-equatorial transects in context of moored data

- Timeline of PUMP IOPs (from PUMP SIP)

## Surface forcing

- High-resolution QuikSCAT winds capture positive band of divergence and curl north of equator

## Surface forcing

- However, the positive divergence and curl are coupled to real TIWs and could anomalously force model TIWs

## Surface forcing

- Force the model with temporally smoothed climatological winds (retain zonal bands of positive divergence & curl)

- Fit 4 harmonics of
- annual cycle to
- QuikSCAT wind stress

## Local east/west anomaly

- Localized wind anomaly superimposed on seasonal cycle winds
- Anomaly ramps up over period of a month and then decays
- Runs short to avoid reflected waves
- Is response to anomaly linear? symmetric?

## Poseidon seasonal cycle results

- Zonal decorrelation scale along 140W: temperature

## Poseidon seasonal cycle results

- Meridional decorrelation scale along 140W: temperature