TOPAZoperations, products, ongoing

developments

Laurent Bertino, Knut Arild Lisæter,Goran Zangana, NERSC

OPNet meeting, Geilo, 6th Nov. 2007

The TOPAZ model system TOPAZ3: Atlantic and Arctic

HYCOM EVP ice model coupled 11- 16 km resolution 22 hybrid layers

EnKF 100 members Sea Level Anomalies (CLS) Sea Surface Temperatures Sea Ice Concentrations (SSM/I) Sea ice drift (CERSAT)

Runs weekly since Jan 2003 ECMWF forcing (T799)

Principle of the EnKF

To assimilate one observation one needs to know the error statistics: Which model variables to update? Over which area and depth?

We ignore most of that, but We assume we know the sources of errors

We set arbitrary error statistics for them Ensemble representation (emulation) of the errors

The error statistics and the impact of assimilation depend on our prior assumption on the error sources.

Sequential data assimilationRecursive Monte Carlo method

Forecast Analysis

Observations

1. Initial uncertainty

2. Model uncertainty

3. Measurement uncertainty

12

3

Member1

Member2

Member99

Member100

10d Forecast

Operator’s week

Tuesday Get ocean data + QC Start assimilation + QC Log status to text file

Wednesday Start 10d forecast + QC

Generate products Start ensemble forecast

Friday Generate “best guess”

products Cleanup

Automatic (cron deamon) Download and convert

ECMWF files (daily) Transfer files to

OPeNDAP Backup files to archive

E-mails standard output to the “calldesk” mersea-contact@nersc.n

o

The State Space

2D variables (800 x 880 grid cells) Barotropic pressure, u/v velocity, ice concentration, ice

thickness

3D variables (800 x 880 x 22 grid cells) Temperature, salinity, u/v current, layer thickness

TOTAL: n = 81.000.000 state variables 100 members in double precision = 60 Gb

The observations

Sea level anomalies – SLA (satellite, radar altimeters): CLS Non linear function of state variables 100.000 observations every week

Sea-surface temperature – SST (satellite, optical): NOAA 8.000 observations every week

Sea-ice concentrations (satellite, microwave): NSIDC 40.000 observations every week

Sea-ice drift (AMSR-E, QuickSCAT): CERSAT/Ifremer 80.000 observations every week

TOTAL: m=228.000 obs Coming up: in-situ profiles (10.000 obs.), HR SST (120.000 obs.), HR

ice conc. (160.000 obs.) …

Computations2 recursive steps

Propagation (HYCOM) Embarrassingly parallel 1 job per member

13 Gb 1 node x 1h 100x 16 CPU (4x8

OpenMP/MPI) SMT is used

1600 CPU hours / week

Analysis (EnKF) Sequential, 3 datasets MPI parallelization needed

on Njord (<13Gb constraint) 8 CPUs, 1:30 each dataset

MPI-parallel output Post-processing jobs to

assemble the EnKF output 16 CPUs, 30 min each dataset

72 CPU hours / week

Incoming data volume

Ocean observations SSM/I

NSIDC: 7 Mb per week Merged SLA maps

Aviso: 3.8 Mb per week SST

NOAA: 0.5 Mb per week OSTIA: 10 Mb

In-situ Coriolis: 5-10 Mb per week

Negligible download / processing time Less than a minute

Atmospheric fields ECMWF T799 (1/4th deg)

1d analysis + 10d forecast 5 variables 1.2 Gb per day About 1h for download &

pre-processing Potential issue for daily

runs

The Products

MERSEA standard productsForecast for the Tara expedition

MERSEA Product generation

Conversion to NetCDF 1.2 Gb per week Past forecast overwritten by new best guess

File server External to NERSC (Parallab) 90 Gb produced every year Limited by disk space

MERSEA productsAll are derived from HYCOM daily averages

Class1 3D daily fields (U,V, T, S) 15 fixed depths 2D Surface fields (SSH, sea

ice …) 25 km output grid

Class2 2D daily sections Moorings Same variables as Class1 33 fixed depths

Class3 Time series of integrated

variables Water mass transports

(Atlantic water …) Sea Ice transports Other: MOSF, ice area, volume

Class4 Model-minus observations Coriolis T/S profiles SSM/I ice concentrations Next: Tide gauge, SST, ...

Documented in MERSEA WP5

Examples of output

Sea-ice minimum 2007

RMS errors - Example for the Barents Sea Ice

Analysis better than forecast Forecast better than

persistence See http://topaz.nersc.no

A non-MERSEA product

TOPAZ successive forecasts in red Actual positions of Tara from DAMOCLES in black Updated on Google Earth [ K. A. Lisæter]

Arctic sea-ice area minimum

Forecasting the ice minimum in TOPAZ

Conclusion

First operational application based on the EnKF inside Europe (so far only in USA and Canada) Installed on Met.no’s facilities (Njord) Code and restart files provided to met.no Scheduling shell scripts

Self-documented, but documentation not up-to-date.

Some tasks can be done in parallel Setting up the OPeNDAP/THREDDS

View the differences with NERSC TOPAZ on a LAS Scheduling the jobs in the operational suite

Start from the main script and descend into dependencies