GODAE Final Symposium, 12 – 15 November 2008, Nice, France

Global High Resolution Analyses and Forecasts at the Mesoscale

H. Hurlburt1, Y. Drillet2, G. Brassington3, M. Benkiran4, E. Chassignet5, J. Cummings6, M. Drevillon7, H. Etienne4,

O. Le Galloudec2, E.J. Metzger1, P. Oke8, T. Pugh3, A. Schiller8, J.F. Shriver1, O.M. Smedstad9, B. Tranchant7,

A. Wallcraft1, G. Warren10

1Naval Research Laboratory, Stennis Space Center, MS, USA2Mercator-Océan, Ramonville Saint Agne, France

3Centre for Australian Weather and Climate Research, BoM, Melbourne, Australia4CLS, Ramonville Saint Agne, France

5Florida State University, COAPS, Tallahassee, FL, USA6Naval Research Laboratory, Monterey, CA, USA

7CERFACS, Toulouse, France8Center for Australian Weather and Climate Research, CSIRO, Hobart, Australia

9Planning Systems Inc., Stennis Space Center, MS, USA10Bureau of Meteorology, Melbourne, Australia

2004-2006 Sea Surface Height (SSH) Variability

From satellite altimetry

(CLS)

From a 1/12 Mercator Océan

simulation without data assimilation (using the

NEMO model)

(in m2)

SSH Variability in the Gulf Stream Region

45N

40N

35N

30N

45N

40N

35N

30N

80W 70W 60W 50W 40W

4 years from 1/12 global HYCOM

with climatological forcing and no

data assimilation

Along altimeter tracks in 4 orbits spanning 2000-

2007. From Hurlburt and

Hogan (2008, DAO) courtesy Gregg Jacobs (NRL).

MODIS Ocean Color vs 10-day Gulf Stream Region Current Speed Forecasts from 3

Mercator-Océan Systems on 23 April 2008

MODIS

1/12 global1/4 global

1/12 Atlantic

All the Mercator Océan systems use the NEMO model and SEEK data assimilation

East Australian Current System on 8 March 2007

1/10 Operational BLUElink Nowcast 1/10 BRAN 2.2 Reanalysis

± 2-day drifter trajectories overlaid on sea level anomalies and ocean currents

Both are global with 1/10 resolution in the Australian region (90E-180E, 75S-16N) and use MOM4 with multivariate EnOI data assimilation

GODAE Final Symposium, 12 – 15 November 2008, Nice, France

1/10 Operational BLUElink Nowcast 15 Feb 2007 – 30 Apr 2007

Eddies in Ocean Model Nowcasts vs SeaWiFS Ocean Color in the Northwestern Arabian Sea and

Gulf of Oman on 6 Oct. 2002

Adapted from Hurlburt et al. (2008; AGU Monograph 177)

Eddies in Ocean Model Nowcasts vs SeaWiFS Ocean Color in the Northwestern Arabian Sea and

Gulf of Oman on 6 Oct. 2002

Adapted from Hurlburt et al. (2008; AGU Monograph 177)

Prediction SystemResolution at 20N

1/16 NLOM8 km

1/32 NLOM4 km

1/8 NCOM18 km

1/12 HYCOM8km

1/32 NLOMn No Assim

% of Eddies Present in the Model

All eddies 70 90 55 80 35

Large eddies, 1-10 80 100 80 90 20

Small eddies, 11-20 60 80 30 70 50

Median Eddy Center Position Error, km

All eddies 35.5 29 48 50 42

Large eddies 42.5 37 57 68 38

Small eddies 32.5 22.5 47 44 42

Eddies in Ocean Model Nowcasts vs SeaWiFS Ocean Color in the Northwestern Arabian Sea and

Gulf of Oman on 6 Oct. 2002

Adapted from Hurlburt et al. (2008; AGU Monograph 177)

(in cm)

24°N

22°N

20°N

18°N

16°N

26°N

24°N

22°N

20°N

18°N

16°N

26°N

56°E 58°E 60°E 62°E 56°E 58°E 60°E 62°E 56°E 58°E 60°E 62°E

29 Sept 2002 6 Oct 200222 Sept 2002

1/32 NLOM Nowcast SSH and Currents with Altimeter Tracks Overlaid

Altimeter track data from ERS-2 (red), GFO (black), and JASON-1 (white) were assimilated daily using a 3-day data window and the model as a first guess Altimeter tracks are overlaid with the most recent seven days as solid lines Daily MODAS SST analyses are also assimilated Atmospheric wind and thermal forcing is from FNMOC/NOGAPS

Adapted from Hurlburt et al. (2008; AGU Monograph 177)

1/12 Global HYCOM forecasts vs. Verifying Analyses

20 Forecasts included in statistics* Reverts toward climatology at end of atmospheric forecast.

Atmospheric analysis forcing operational forcing* persistence

WorldOcean

Gulf Stream NW Arabian Sea and Gulf of Oman

EquatorialPacific

Kuroshio Yellow and Bohai

Seas north of

30N

1.0

0 10 20 30 10 20 30 10 20 30

Forecast length (days)

1.0

0.9

0.8

0.7

1.0

0.9

0.8

0.7

0.6

Med

ian

SS

H a

no

mal

y co

rrel

atio

n

Partly from Hurlburt et al. (2008; AGU Monograph 177)

Verification of 30-day Forecasts of SSH vs Unassimilated Tide Gauge Data

1/12 HYCOM, with analysis quality forcing

1/12 HYCOM, with operational forcing

1/32 NLOM 1/16 NLOM

Adapted from Hurlburt et al. (2008; AGU Monograph 177)

Open Ocean Islands Coastal Both

A 13-day moving average was applied to filter time scales not resolved by the altimeter data

0 .5 1.0C

Mercator Océan Atlantic SST Forecast Error vs SST Analysis

1-day RMS Error 7-day RMS Error

Length of Forecast (days)

RM

S E

rro

r (C

) persistence

forecast

Strong Coastal Upwelling Event off Southern Australia

Observed SST

Organisations

Bonney coast off South Australia is a location of frequent coastal upwelling

The upwelling in Feb 2008 was one of the largest events ever recorded

10 Feb 2008 BLUElink SST 10 Feb 2008

MODIS ocean color 30 Mar 08

Australia

15 Jan – 15 Feb mean winds

Organisations

• South Australia non tidal sea level exceeded 0.6m, 29 th October 2007

• Tasmania, Derwent River, non tidal signal ~0.4m, 9th August 2007

• Hobart Mercury, 10th August 2007 “WILD weather and huge downpours continue to flood three major valleys in Tasmania, triggering car crashes, fires and a dangerous landslide.”

Sea Level Anomaly

BLUElink Prediction of Coastal Trapped Wave Events around Australia

Organisations

Non

-tid

e re

sidu

al (

m)

South Australia, Thevenard coastal tide gauge

Comparison of OceanMAPs () and non tidal sea level CTG ()

BLUElink Coastal Trapped Wave Nowcast Accuracy at the Thevenard, Australia Coastal Tide Gauge

Thevenard

RM

SE

(m

)

Forecast period (days)

BLUElink Coastal Trapped Wave Forecast Accuracy around Australia