42
Slide 1 Workshop working groups: Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Modelling: Coupling. How to deal with multi scales. Dangerous sea states. Physics Dissipation. Non linear source term. Wave effect on the oceans. Wave/current interaction. Wave under extreme winds. New source terms. Data Analysis and re-analysis. Future satellite missions. Validations techniques. Forecast products.

Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

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Page 1: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 1

Workshop working groups:

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Modelling:

Coupling.

How to deal with multi scales.

Dangerous sea states.

Physics

Dissipation.

Non linear source term.

Wave effect on the oceans.

Wave/current interaction.

Wave under extreme winds.

New source terms.

Data

Analysis and re-analysis.

Future satellite missions.

Validations techniques.

Forecast products.

Page 2: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 2

PRESENT STATUS of WAVE FORECASTING

AT E.C.M.W.F.

Jean-Raymond Bidlot

Marine Aspects Section

European Centre for Medium-range Weather Forecasts

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Page 3: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 3

Symmetric Slope

2001 2011

Introduction: sustained improvement over the years

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

For example: global wave height forecast against buoy measurements:

analysis

1 day FC

3 day FC

5 day FC

7 day FC

In-situ wave observations

Scatter Index

2001 2011

Page 4: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 4

Limited extend.

11 km grid spacing.

Stand alone.

Forced by 10m neutral wind fields.

Use surface currents from TOPAZ4.

Data assimilation of altimeter data.

2 daily forecasts extending to day 5.

Output every hour, including spectra

(*).

ECMWF Wave Model Configurations

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

1) Limited Area Wave model (LAW)

TOPAZ4

surface currents

Page 5: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 5

Global.

Coupled to the atmospheric model.

Data assimilation of altimeter data.

Part of all forecasting components

(high resolution, ensemble,

monthly, seasonal, re-analyses)

ECMWF Wave Model Configurations

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Atm

osp

heri

c

mo

de

l

Wa

ve

mo

de

l

neutral wind

wind gustiness

air density

roughness

Stokes drift

2) Global models

Global from 81°S to 90°N

Page 6: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 6

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

ECMWF Wave Model Configurations

Ensemble forecasts

55 km grid spacing.

30 25 frequencies *.

24 12 directions *.

Coupled to TL639 (32 km)

TL319 model *.

(50+1) (10+5) day forecasts from

0 and 12Z (monthly twice a

week).

High resolution

28 km grid spacing.

36 frequencies.

36 directions.

Coupled to the TL1279 model

(16km).

Analysis every 6 hrs and 10 day

forecasts from 0 and 12Z. * Change in resolutions after 10 days

NB: also in seasonal forecast at lower resolutions

Page 7: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 7

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Ocean Wave Modelling: ECWAM

The ocean wave modelling at ECMWF is based on the wave

mode WAM cycle 4 (Komen et al. 1994), albeit with frequent

improvements.

Wave model page on the Centre‟s web site:

http://www.ecmwf.int/products/forecasts/wavecharts/index.html#forecasts

General documentation:

http://www.ecmwf.int/research/ifsdocs/CY36r1/index.html

Page 8: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 8

Latest upgrade to operational system (CY38R1)

(19 June 2012):

Wave model main changes:

- Sinput + Sdiss + Sbottom

- Bug fix to wave stress table.

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

with bug corrected

Drag Coefficient versus wind speed (coupled runs):

Page 9: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 9

Wave height (m)

Stdev

error

N.H.

Compared to model analysis:

CY38R1: wave scores

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Mean wave period (s)

Positive = improvement

old

new

Bias (m)

S.H.

Scatter Index

S.H.

Compared to altimeter data:

Page 10: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 10

Comparison with 17 operational centres at a set of buoys as part of the

activities of JCOMM Expert Team on Waves and Storm surges (ETWS):

Wave height

Wind speed

Peak period

Global systems at all buoys, February-May 2012:

ECMWF old

Bias (model-obs) Scatter Index

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Page 11: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 11

Comparison with 17 operational centres at a set of buoys as part of the

activities of JCOMM Expert Team on Waves and Storm surges (ETWS):

Wave height

Wind speed

Peak period

Global systems at all buoys, February-May 2012:

ECMWF new

Bias (model-obs) Scatter Index

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Page 12: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 12

CY38R1: comparison with buoy spectra

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

CY37R3

CY38R1

Data from NDBC (US), ISDM (Canada), CDIP (US)

Page 13: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 13

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Present status of ECWAM:

The 2-D spectrum F(f,θ) follows from the energy balance

equation (in its simplest form: deep water case):

where the group velocity Vg is derived from the dispersion

relationship which relates frequency and wave number.

dissnling SSSFt

F

V

Sin: wind input source term (generation).

Snl: non-linear 4-wave interaction (redistribution).

Sdiss: dissipation term due to whitecapping (dissipation).

Page 14: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 14

Grid and Advection:

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Irregular lat-lon grid to keep the distance

between grid points roughly constant

Corner Transport Upstream scheme:

Unresolved bathymetry obstructions:

Model bathymetry:

Obstructions for low frequency from South:

Page 15: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 15

Wind input Sin:

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

based on Janssen (1991):

))(cos(

ln*

2

zc

uc

gzZ o

where Z is the effective wave age:

βmax = 1.2 (as before)

oz

uU

10ln*

10

neutral 10m wind U10

*u

von Karman constant

oz

friction velocity

surface roughness

Fc

uZeS Z

w

ain 0 ),cos( max

2

*4

2

max

air density

zα : wave age tuning parameter:

zα = 0.008 (0.011 before CY38R1) New:

roughness oz

a

w

air density

water density

wind direction,

c phase speed,

),( fF

g

sea state dependent

Page 16: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 16

Wind input Sin:

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

FSin

c

u*

0 ),cos( max

2

*

c

u

w

a

4

2

max ZeZ

Page 17: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 17

Wind input Sin: gustiness parameterisation

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

wind gustiness FSin

**2

*

2

**

*

* )( 2

)( exp

2

1)( duu

uuu

)( )( 5.0)( ***** uuu

3/13

10

10

** 5.0

10 08.0 5.01

L

zb

C

U

U

u i

d

10

3 10)08.08.0( UCd

* : standard deviation of u*

10* UCu d

iz Inversion height

L Monin Obukhov length

from the atmospheric model :

0b

Page 18: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 18

Wind input Sin: linear swell damping

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

FSin

)cos(20 ),cos( max

2

*

2

*

V

c

c

u

c

u

w

a

V : wind speed at height z = 1/k

Following Janssen (2004), the small effect of turbulent eddies

on the waves can be modelled as

Page 19: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 19

Sdiss

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Sdiss following Bidlot, Janssen and Abdalla (BJA) 2007,

back to Komen et al. 1994 form:

2

2

0

2 )1( meanmean

meanmeandsdiss

k

k

k

kmkCS

33.1dsC 5.0

0

m

dfdFmean

0

m

dfdFkkmean

dfdFm 0

Page 20: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 20

Snl:

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

deep ),(shallow nlnl TransfhkfTransf

The calculation of the non linear source term is still based on the Discrete

Interaction approximation (DIA).

For shallow water, the transfer coefficients are re-scaled:

Following Janssen and Onorato (2005), using the narrow band approximation, it was

shown that the scaling factor could be written as

)1()(4)]1([ 22222 TTkhTkhTk

vg

where

),tanh(khT ,))2sinh(

21(5.0

kh

khcgv ,

kc

,ghsc gkT

2

k

vT

Rhkf

g

8

2

),(

Page 21: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 21

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Shallow water Snl

1

)2/2(1

8

910922

2

3

24

gs

g

vc

cv

khT

TTR

k

vT

Rhkf

g

8

2

),(

),tanh(khT

,))2sinh(

21(5.0

kh

khcgv

,k

c

,ghsc

gkT2

0 1 2 3 4

kD

0

2

4

6

8

R^2

Depth dependent correction factor Kinetic Equation

Eq. (39) (no wave-induced current)

Eq. (39) (with wave-induced current)

kh=1.363

2R

Page 22: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 22

Sbottom:

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Sbottom (see Komen et al. 1994):

) 2 sinh( 2

hk

kCS botbottom

gCbot

038.0

Page 23: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 23

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Bottom induced wave breaking:

Dissipation due to bottom induced wave breaking was added to the source

terms. Following Battjes, Janssen and Beji:

( , )dis BJ bS C Q f F f

hH maxH

H

s2

2max2

wavesbreaking offraction : bQ

6.0 rameterbreaker pa

1BJC encymean frequf

)1(exp bb QQ

Page 24: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 24

Coupling to the waves: Warm skin layer model

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Following Takaya et al. (JGR 2010), a skin layer model is used to represent

the Daily SST Amplitude.

In this scheme, the temperature profile is controlled by the turbulent

diffusivity Kw(z):

)/(

)( )(

*

Lz

LfuzzK

h

aww

Following Grant and Belcher (JPO 2009),

for stable condition only and for f(La) >1:

3/2

1)(

a

aL

Lf

Stokes

wa

U

uL

*

Langmuir number

*

wu )/( Lzh: friction velocity in water : similarity function, L: Obukhov length

Stokes drift

Page 25: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 25

Data assimilation:

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Currently only using Jason-2 wave heights.

Resuming use of Jason-1 under evaluation.

Still using the Optimum Interpolation scheme from Lionello et al.

(1992).

Some minor adaptations:

Page 26: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 26

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Land recognition:

Hs analysis

increments

default Land detected

The model background error should recognize the presence of land

Page 27: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 27

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Shallow water spectral update:

Egu

E )(2

4

* *

tgut )/*(*

But in shallow water

E* is limited by depth,

Hence use deep water

relation but only to

E*max

E*max

dgu

d )( *2

*

Egu

E )(2

4

* *

fugf *)/(*

Windsea update relies on deep water model growth curves in order to

determine an update to u* and mean frequency:

Page 28: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 28

Data assimilation

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Impact still limited:

Jason-2 + ENVISAT

Jason-2

ENVISAT

No data

Page 29: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 29

Products:

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

All “standard” wave parameters in the operational catalogue.

Including wave spectra.

A few „freak wave parameter‟, including Hmax.

New set of parameters to include wave effects on the ocean

fluxes:

Page 30: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 30

New parameters:

A small portion of the stress is retained by the wave field to be

released later.

Hence, one can compute the stress that is actually acting on the

oceans.

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Monthly mean of the normalised stress into the ocean

as derived from ERA-Interim data

ua

2

*It is normalised by

Page 31: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 31

New parameters

Similar consideration can be made for the energy fluxes passing first

into the waves.

It is then dissipated by the waves and transferred into the upper

oceans where it will contribute to the mixing of the top of the oceans.

Both quantities are connected to the wave model source terms.

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Monthly mean of the normalised energy

flux into the ocean

as derived from ERA-Interim data.

ua

3

*It is normalised by

Page 32: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 32

Can we still improve ?

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Comparison to buoy spectra,

stratified by energy level:

Comparison to altimeter wave heights :

Bias

SI

Latest CY38R1 compared to observations, January to May 2012

Page 33: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 33

Can we still improve ?

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Shallow water issues:

62042: UK CEFAS buoy, located on the north shore of East Anglia

in 18m of water

Page 34: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 34

Ongoing developments:

Integration of the atmosphere-wave-ocean models.

Unstructured grid option.

Sea ice damping.

Sbottom.

Many more following this workshop…

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Page 35: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 35

Future developments: unstructured grid

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Page 36: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 36

Future developments: unstructured grid

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Page 37: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 37

Future developments: unstructured grid

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

20 m/s

Page 38: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 38

Future developments: sea ice damping:

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

D2

a ciα

From Kohout and Meylan (JGR 2008), Figure 6.

h The non-dimensional

attenuation

coefficient “a” was

found to depend only

on wave period and

sea ice thickness “h”

Page 39: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 39

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Hs (m)

Tp (s)

Tm (s)

Raw buoy data

(further QC still needed!)

Model,

with wave propagation only

When sea ice cover > 30%

Model,

with sea ice damping

up to sea ice cover of 90%

(ciblock=0.9)

Page 40: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 40

Questions/comments?

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

Page 41: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 41

New decomposition:

Future developments: spectral partitioning

Workshop on Ocean Waves, ECMWF, June 25-27, 2012

windsea

Swell 1

Swell 2

Swell

windsea total

Operational:

Page 42: Workshop working groups - ECMWF · Slide 23 Workshop on Ocean Waves, ECMWF, June 25-27, 2012 Bottom induced wave breaking: Dissipation due to bottom induced wave breaking was added

Slide 42

Verification against buoy frequency spectra

f

E(

f )

area under spectrum = <2>

2

4H s

where A is the

area under curve for

a given frequency bin

Hs,

significant wave height. EWH,

Equivalent Wave Height

for a given frequency bin:

AEHW 4

EWH for waves with

periods between

17s and 19s.

EWH for waves with

periods between

5.5 s and 6.0 s.

Workshop on Ocean Waves, ECMWF, June 25-27, 2012