fleet numerical meteorology & oceanography center ......ncep and fnmoc ww3 ensembles ncep fnmoc...

Michael SestakMeteorologist

Fleet Numerical Meteorology & Oceanography Center

FNMOC/NCEP WW3 Ensemble Status

17 May 2010

Fleet Numerical…Supercomputing Excellence for Fleet Safety and Warfighter Decision Superiority…


With the assistance of

Stephen Klotz, DoD HPCMO

Paul Wittmann, FNMOC

Arun Chawala, NCEP

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OVERVIEW

• Wavewatch 3

– Basic model information

– NCEP and FNMOC ensembles

• Sample products

• Preliminary evaluation

– Ensemble mean statistics

– Ensemble distribution statistics

• Summary


Wavewatch 3 version 3.14

• solves the random phase spectral action density balance equation for wavenumber-

direction spectra.

• Rectangular latitude longitude grid

• 24 directions, 29 frequencies at each grid point

• refraction and straining of the wave field due to temporal and spatial variations of the

mean water depth and of the mean current (tides, surges etc.)

• Parameterizations of physical processes (source terms) include wave growth and decay

due to the actions of wind, nonlinear resonant interactions, dissipation (`whitecapping'),

bottom friction, surf-breaking (i.e., depth-induced breaking) and scattering due to wave-

bottom interactions including shallow water

• sub-grid representation of unresolved islands

• dynamically updated ice coverage

• Up to 9 restart files per model run

• Multiple one-way nested or two-way nested runs

• Serial, MPI and OpenMP versions

• Tolman, 2009: User manual and system documentation of WAVEWATCH III™ version

3.14. NOAA / NWS / NCEP / MMAB Technical Note 276, 194 pp + Appendices

• http://polar.ncep.noaa.gov/waves/wavewatch/wavewatch.shtml

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NCEP and FNMOC WW3 Ensembles

NCEP FNMOC

Grid 1x1 degree 1x1 degree

Members 20 20

Forecast 00Z, 06Z,12Z, 18Z for 240 hr 00Z and 12Z for 240 hr

Wind forcing Bias corrected GEFS 10 m winds Raw NOGAPS EFS 10 m

winds

History From each member From each member

Data assimilation None In control only, satellite

altimetry and buoys

Perturbations None None

Ice concentration/

edge and SST

GDAS NCODA

Update Cycle 6 hr 12 hr

Same bathymetry, subgrid islands, coastlines

http://polar.ncep.noaa.gov/waves/ensemble/viewer.shtml

https://www.fnmoc.navy.mil/efs/efs_ww3.html

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FNMOC and NCEP Sample Graphic Products

• Significant Wave Height Ensemble Mean and Spread

• Probability of Wave Height Exceeding a Threshold

• http://polar.ncep.noaa.gov/waves/ensemble/viewer.shtml

• https://www.fnmoc.navy.mil/efs/efs_ww3.html

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NCEP Sample Wave Height Plot

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FNMOC Sample Wave Height Plot

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NCEP Sample Wave Probability Plot

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FNMOC Sample Wave Probability Plot

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NCEP Ensemble Mean Skill

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NCEP Ensemble Spread

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NCEP Ensemble Mean & Spread vs Obs

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Obs are generally in ensemble range, ensemble mean generally outperforms

deterministic control, clear change in predictability at 100h, with waves lagging

winds


FNMOC Ensemble Skill

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0

0.05

0.1

0.15

0.2

0.25

0.3

0 24 48 72 96 120 144 168 192 216 240

Bri

er

Sco

re

Forecast lead time (hr)

Significant Wave Height Brier Score

for North Atlantic (10N-70N 100W-15E) , March 2010

> 6 ft

> 12 ft

> 18 ft

0.9

0.91

0.92

0.93

0.94

0.95

0.96

0.97

0.98

0.99

1

0 24 48 72 96 120 144 168 192 216 240

Co

nti

nu

ou

s R

an

k P

rob

ab

ilit

y S

core

Forecast Lead Time (hr)

Significant Wave Height Continuous Rank Probability Score

for North Atlantic (10N-70N 100W-15E) , March 2010


FNMOC Ensemble Skill

15

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50000

100000

150000

200000

250000

300000

0

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0.2

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0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Fo

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st c

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nts

Ob

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Fre

qu

en

cy

Forecast Probability

Reliability Diagram for Feb, 2010, North Atlantic (10-70 N 100W-15E)

Probability of Significant Wave Height > 6 ft (1.2 m) 144 hr Forecast

0

1000

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5000

6000

7000

8000

9000

10000

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Forecast Probability

Reliability Diagram for Feb, 2010, North Atlantic (10-70 N 100W-15E)

Probability of Significant Wave Height > 18 ft (5.5 m) 144 hr Forecast


Summary

• Thus far, simple individual member driven wave model ensembles appear promising, though both initial condition and model uncertainty are likely to add skill

• Both NCEP and FNMOC are in the process of developing both products and verification systems for combined WW3 ensemble products

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Questions ?


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BACK-UP SLIDES


• In the Feb 2010 WW3 innovation data there are :

• 40,374 wave height obs > 6ft



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