Strategy for seasonal prediction developments at ECMWF

JMA WS (9 Dec 2010) - Roberto Buizza et al : Strategy for seasonal prediction developments at ECMWF 1

Strategy for seasonal predictiondevelopments at ECMWF

Roberto Buizza, Franco Molteni, Magdalena Balmaseda,

Thomas Jung, Linus Magnusson, Kritian Mogensen, Tim Stockdale, Yuhei Takaya* and Frederic Vitart

European Centre for Medium-Range Weather Forecasts

(* Visiting scientist at ECMWF in 2009, now back at CPD of JMA)


Outline

1. ECMWF current and future seasonal systems S3 and S4

2. Recent results from 46-day EPS coupled integrations

3. Model error simulation schemes

4. Model improvements (e.g. convection in the tropics, stratosphere), inclusion

of a mixed-layer and a dynamical sea-ice model

5. Conclusions: potential future strategy for seasonal prediction


Delayed Ocean Analysis ~12 days

Real Time Ocean Analysis ~8 hours

HRESTL1279L91 (d0-10)

HRESTL1279L91 (d0-10)

SFTL159L62 (m0-7/12)

SFTL159L62 (m0-7/12)

EPSTL639L62 (d0-10)

TL319L62 (d10-15/32)

EPSTL639L62 (d0-10)

TL319L62 (d10-15/32)

Atmospheric model

Wave model

Ocean model

Atmospheric model

Wave model

1. Baseline operational systems (2010)


1. The ECMWF systems

# fcs Hor resolution Vert lev Fc length Wave OceanHRES/DA 1 T1279 16 km 91 (<0.01 hPa, 75km) 0-10d WAM (0.25°, 28km) No

EPS 51T639 32 km

62 (<5 hPa, 35km)0-10d

WAM (0.5°, 56km)No

T319 64 km 10-15/32d HOPE 0.3-1.4 deg L29S3 41 T159 125km 62 (<5 hPa, 35km) 0-13m No HOPE 0.3-1.4 deg L29


1. ECMWF operational system S3

OASIS-2HOPE

~ 1.4 deg. lon1.4/0.3 d. lat.

TESSEL

IFS 31R11.1 deg. 62 levels

4-D variational d.a.

Multivar. O.I.

Gen. ofPerturb.

System-3CGCM

Initial Con. Ens. Forecasts


1. The new seasonal forecasting system S4

OASIS-3NEMO

~ 1.4 deg. lon1.4/0.3 d. lat.

H-TESSEL

IFS 36R40.7/1.1 deg.

91 levels

4-D variational d.a.

3-D v.d.a. (NEMOVAR)

Gen. ofPerturb.

System-4CGCM

Initial Con. Ens. Forecasts


1. System 4: main features

It is expected that S4 will improve the quality of seasonal forecasts thanks to the combined contribution of:

A new ocean model: NEMO v3.0 + 3.1 coupling interface:

ORCA-1 configuration (~1-deg. resol., ~0.3 lat. near the equator) 42 vertical levels, 20 levels with z < 300 m

Better ocean ICs with variational ocean data assimilation (NEMOVAR):

3-D var with inner and outer loop Collaboration with CERFACS, UK Met Office, INRIA First re-analysis (1957-2009), no assim. of sea-level anomalies Second re-analysis and real-time system including SLA

Better atmospheric model cycle (IFS cycle 36r4):

New physics package, including HTESSEL land-surface scheme, snow model (with EC-Earth), new land surface initialization

Prescribed sea-ice conc. with sampling from recent years


Outline








The Madden-Julian Oscillation (MJO) is a 40-50-day oscillation with peak activity during NH winter and spring. It is a near-global scale, quasi-periodic eastward moving disturbance in the surface pressure, tropospheric temperature and zonal winds over the equatorial belt.

The MJO is the dominant mode of variability in the tropics in time scales in excess of 1 week but less than 1 season.

The MJO influences the Indian and Australian summer monsoons (Yasunari 1979, Hendon & Liebman 1990). It has an impact on ENSO. Westerly wind bursts produce equatorial trapped Kelvin waves, which have a significant impact on the onset and development of an El-Niňo event (Kessler & McPhaden 1995). It has an impact on tropical storms (Maloney et al 2000, Mo 2000) and on NH weather.

Recent results have indicated that the 32d EPS has an improved description of the MJO and is capable to capture at least part of the tropical/extra-tropical interaction due to the MJO. These improvements supports the potential further extension of the EPS to 46-60 days.

2. The MJO and the skill over the NH extra-tropics


These plots show OLR anomalies in ERA-40 (left panel) and in 15d forecasts run (from 29 Dec to 12 Feb) with different model cycles from 28r3 (ope in Oct ‘04) to 35r3 (ope from Sep ‘09 to Jan ‘10).

More recent cycles (from 32r2) are better capable to simulate MJO activities.

29/12

05/01

12/01

20/01

28/01

04/04

12/02

32R3

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30E 90E 150E 150W 90W 30W

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ERA40

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15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

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Ensemble meanewku

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15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

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Ensemble meanex6i

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15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

ERA40

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ERA40

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15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

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Ensemble meanewku

10

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-10

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-10

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

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LONGITUDE

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Ensemble meanex6i

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-10

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

days

28R3 29R1 31R1 32R2

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LONGITUDE

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ERA40

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-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

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Ensemble meanewku

-10

-10

-10

-10

-10

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

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30E 90E 150E 150W 90W 30W

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30E 90E 150E 150W 90W 30W

Ensemble meanex6i

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-10

-10

-10

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

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30E 90E 150E 150W 90W 30W

LONGITUDE

30E 90E 150E 150W 90W 30W

ERA40

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-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

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LONGITUDE

30E 90E 150E 150W 90W 30W

Ensemble meanelz5

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

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30E 90E 150E 150W 90W 30W

Ensemble meanek7h

-10

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

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LONGITUDE

30E 90E 150E 150W 90W 30W

ERA40

10

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-10

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-10

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15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

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30E 90E 150E 150W 90W 30W

LONGITUDE

30E 90E 150E 150W 90W 30W

Ensemble meanelz5

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

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30E 90E 150E 150W 90W 30W

LONGITUDE

30E 90E 150E 150W 90W 30W

Ensemble meanek7h

-10

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/02

31/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/01

31/1230/1229/12

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25

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30E 90E 150E 150W 90W 30W

LONGITUDE

30E 90E 150E 150W 90W 30W

ERA40

10

-10

-10

-10

-10 -10

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/0231/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/0131/1230/1229/12

30

25

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30E 90E 150E 150W 90W 30W

LONGITUDE

30E 90E 150E 150W 90W 30W

Ensemble meanes8c

-10

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/0231/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/0131/1230/1229/12

30

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30E 90E 150E 150W 90W 30W

LONGITUDE

30E 90E 150E 150W 90W 30W

Ensemble meaner98

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/0231/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/0131/1230/1229/12

10/04 04/05 09/06 06/07

11/07

30

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30E 90E 150E 150W 90W 30W

LONGITUDE

30E 90E 150E 150W 90W 30W

ERA40

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/0231/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/0131/1230/1229/12

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30E 90E 150E 150W 90W 30W

LONGITUDE

30E 90E 150E 150W 90W 30W

Ensemble meanf4i5

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/0231/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/0131/1230/1229/12

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30E 90E 150E 150W 90W 30W

LONGITUDE

30E 90E 150E 150W 90W 30W

Ensemble meanf1xi

10

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/0231/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/0131/1230/1229/12

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30E 90E 150E 150W 90W 30W

LONGITUDE

30E 90E 150E 150W 90W 30W

ERA40

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/0231/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/0131/1230/1229/12

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30E 90E 150E 150W 90W 30W

Ensemble meanf4i5

-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/0231/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/0131/1230/1229/12

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30E 90E 150E 150W 90W 30W

Ensemble meanf1xi

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15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/0231/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/0131/1230/1229/12

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LONGITUDE

30E 90E 150E 150W 90W 30W

ERA40

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15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/0231/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/0131/1230/1229/12

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Ensemble meanf46n

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/0231/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/0131/1230/1229/12

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30E 90E 150E 150W 90W 30W

LONGITUDE

30E 90E 150E 150W 90W 30W

Ensemble meanf6ju

10

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-10

15/0214/0213/0212/0211/0210/02 9/02 8/02 7/02 6/02 5/02 4/02 3/02 2/02 1/0231/0130/0129/0128/0127/0126/0125/0124/0123/0122/0121/0120/0119/0118/0117/0116/0115/0114/0113/0112/0111/0110/01 9/01 8/01 7/01 6/01 5/01 4/01 3/01 2/01 1/0131/1230/1229/12

33R1 35R1 35R3

06/08 09/08 09/09

2. The MJO in subsequent IFS cycles


0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1forecast probability

0

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uen

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The skill of probabilistic forecasts of 2mT in the upper tercile for cases with MJO-in-ICs and NO-MJO-in-ICs have been compared (1989-2008). Results based on 45 cases show that the skill of weekly average d19-25 is higher if these is an active MJO in the ICs.

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1forecast probability

0

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uen

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MJO in ICs BSS(EU)=0.03NO MJO in ICs BSS(EU)=-0.09

2. The MJO and the skill over NH in NDJFMA

MJO in ICs BSS(NH)=0.04NO MJO in ICs BSS(NH)=-0.06


2. The MJO and the skill over NH in NDJFMA

0 1 2 3 40

0.05

0.1

0.15

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0.25

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0.35

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0.5

MAGICS 6.12 vancleef - nec Fri Aug 27 11:38:51 2010

DAY 5-11

Z500 T850 Precip

DAY 12-18

Z500 T850 Precip

DAY 19-25 DAY 26-32

0 1 2 3 4-0.1

-0.08

-0.06

-0.04

-0.02

0

0.02

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0.08

0.1

MAGICS 6.12 vancleef - nec Fri Aug 27 12:56:10 2010Z500 T850 Precip Z500 T850 Precip0 1 2 3 4

-0.1

-0.08

-0.06

-0.04

-0.02

0

0.02

0.04


0 1 2 3 4

-0.08

-0.04

0

0.04

0.08

0.12

0.16

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MJO in ICs - NO MJO in ICs MJO in ICs - NO MJO in ICs

MJO in ICs - NO MJO in ICs MJO in ICs - NO MJO in ICs


0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1false alarm rate

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hit

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Day 5-20041007-20041007ECMWF Monthly Forecast, 2-metein upper tercile , Area:Northern Extratropics

ROC score = 0.841ROC score = 0.676

0 0.2 0.4 0.6 0.8 1rel FC distribution

0.121 105

0.241 105

0.362 105

0.482 105

0.603 105

Forecast

Persistence

Persistence

Persistence

2mT

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1false alarm rate

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Day 5-20041007-20041007ECMWF Monthly Forecast, Precipin upper tercile , Area:Northern Extratropics



97200.194 10

5

0.292 105

0.389 105

0.486 105

Forecast

Persistence

Persistence

Persistence

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1false alarm rate

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it r

ate

Day 5-20041007-20041007ECMWF Monthly Forecast, Precipin upper tercile , Area:Northern Extratropics



0.123 105

0.247 105

0.370 105

0.493 105

0.616 105

Forecast

Persistence

Persistence

Persistence

2. 32d EPS scores over NH (ROCA)

MSLP TP

D5-11D12-18D19-25D26-32

D5-11D12-18D19-25D26-32

D5-11D12-18D19-25D26-32

Results based on 45 cases (ICs 4 times a year from ‘91 to ’02, 5m) indicate that 32d EPS weekly average probabilistic forecasts of 2mT and MSLP over NH land points have some level of skill up to forecast day 32. This is shown hereafter for the probabilistic prediction of occurrence of upper tercile values.

Motivated also by these results, work has continued to investigate whether a 46-day extension could provide skilful forecasts up to 6 weeks ahead.


2. Further extension of the EPS to 46 days?

15-member ensembles starting on the 15th of each month from 1991 to 2007 (1979-2008 for the 15th July starting date) have been integrated for 46 days using the same configuration as the operational monthly forecasts.

Results indicate that those forecasts are significantly more skilful than the seasonal forecasts of month 2 issued the same day (15th of the month)

Seas3 EPS

TropicsNorthern Extratropics

Average ROC area for PR(2MT>upper 1/3) computed for all NH land point for DJF.

Blue is the SF d30-61 forecast (available on the 15th of the month).

Red is the EPS d15-46 forecast, which would also be available on the 15th of the month.


Outline








Since 1999, ECMWF has been running its ensemble prediction systems with stochastic schemes designed to simulate model error.

The first version of the stochastically perturbed parameterized tendency (SPPT) scheme implemented in the EPSS in 1999 was designed to simulate the effect of random model errors due to parameterized physical processes. S3 has been running with this scheme.

Since Nov 2010, the EPS has been running with a revised version of SPPT and a stochastic back-scatter scheme (SPBS).

The SPPT revisions (implemented in 2009 and 2010) includes:

Perturbations with 3 different spatio-temporal scales and amplitudes A revised (vertically consistent) treatment of super-saturation A tighter clipping of the Gaussian distribution (2σ instead of 3σ to address

potential numerical instabilities).

It is expected that the inclusion of the revised-SPPT and the BS in S4 should improve its reliability.

3. Stochastic schemes: SPPT


500 km6 h

1000 km3 d

2000 km30 d

3. The multi-scale SPPT (in ope EPS since N10)


Work is continuing to develop a stochastic back-scatter scheme:

Rationale: a fraction of the dissipated energy is backscattered upscale and acts as streamfunction forcing for the resolved-scale flow (Shutts & Palmer 2004, Shutts 2005, Berner et al 2009)

Streamfunction forcing is given by:

Streamfunction forcing

Backscatter ratio

Total dissipation

rate

Pattern generat

or

3. SPBS (in ope EPS since N10)


Outline








ECMWF Model Formulation: )(xx

Mt

Relaxation Formulation: )()( refMt

xxxx

• Relaxation coefficient, λ, depends on latitude, longitude and height.

• xref is based on (linearly interpolated) analysis fields.

4. Tropics and stratosphere (relaxation exps)


(a) MAE D+6-D+10 Z500 CNT

10

20

30

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50

60

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100

120

(b) MAE D+16-D+20 Z500 CNT

20

40

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240

(c) MAE D+26-D+30 Z500 CNT

20

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80

100

120

140

160

180

200

240

(d) MAE D+6-D+10 Z500 TROP-CNT

-40

-25

-15

-5

5

15

25

40

(e) MAE D+16-D+20 Z500 TROP-CNT

-80

-50

-30

-10

10

30

50

80

(f) MAE D+26-D+30 Z500 TROP-CNT

-80

-50

-30

-10

10

30

50

80

(g) MAE D+6-D+10 Z500 STRAT-CNT

-40

-25

-15

-5

5

15

25

40

(h) MAE D+16-D+20 Z500 STRAT-CNT

-80

-50

-30

-10

10

30

50

80

(i) MAE D+26-D+30 Z500 STRAT-CNT

-80

-50

-30

-10

10

30

50

80

CON

TR-CON

STRA-CON

Day6-Day10 Day16-Day20 Day26+Day30

(λ=1.0)

Relaxing the tropics (middle) leads to a reduction of fc error both over NA and EU.

A better representation of the stratosphere (bottom) has also a positive impact over the high-latitudes in the longer forecast range.

4. Tropics, stratosphere and NH-extra-tropics


Y Takaya started implemented the KPP mixed-layer model in the IFS and started the work to assess its impact on the EPS monthly time scale.

Results obtained by Y Takaya (now at JMA) using the KPP model in the tropical band (40°S-40°N) coupled to the atmospheric model grid indicated that in some cases the KPP model improved the simulation of the MJO propagation.

40N30N

30S40S

4. Mixed-layer model


IFS

NEMOLIM2

Oasis 3

Work has started to test the impact of using the Louvain-la-Neuve sea Ice Model (LIM2, http://www.astr.ucl.ac.be/) on long-range integrations. LIM2 is a 2-layer ice model with parameterised ice thickness distribution. Preliminary results indicate that the 8-year average sea-ice extension predicted using LIM2 propagates too far south.

4. Sea-ice modelling

LIM2 OBS


Outline








Conclusions

Recent EPS developments have indicated that the latest model cycles (say since 2008) are more capable to simulate the MJO and to capture the link between the MJO and the extra-tropics. EPS weekly average forecasts of variables such as 2mT and MSLP are skilful up to 4 weeks in advance. EPS d15-46 average fcs issued on the 15th of each month are better than m2 S3 fcs. This suggests that one possible way to generate better monthly outlooks could be to extend the EPS up to 46-60 days.

Work is progressing to assess the impact of using the revised, multi-scale SPPT and the SPBS model error schemes in the seasonal system. This should also lead to seasonal forecast improvements.

Recent relaxation experiments have indicated that improving the tropics (better physics) and the stratosphere simulation can lead to improvements in the NH extra-tropics. This is one of reasons why S4 will use 91 instead of 62 vertical levels and the TOA will be moved from ~5Pa to ~1Pa.


Conclusions

Work will continue to further improve the ECMWF seasonal forecasts by:

1. Implementing the coupled seasonal system 4 (S4) – The new system will use NEMO and NEMOVAR 3D-Var ocean data-assimilation, atmospheric model cycle 36r4 with a better physics and 91 vertical levels with the TOA at 1Pa.

2. Improving the model error simulation schemes in the EPS and SF – Work is progressing to assess the impact of the revised-SPPT and the SPBS schemes on seasonal forecasts.

3. Including a dynamical sea-ice model and a mixed-layer model – Work has started to assess whether using the LIM2 dynamical sea-ice model and a mixed-layer model can lead to further improvements.

4. Merging the EPS and the SF in a Seamless Probabilistic System (SPS) – Once NEMO has been implemented also in the EPS, assess the possibility to merge the EPS and the SF (e.g. by using EPS d15-46 forecast to predict the first next calendar month and then further truncate the resolution).

5. Increasing the resolution of the ocean model - Assess the impact of using a higher-resolution ocean model (1/4 degree NEMO) in the probabilistic forecasting systems.

Documents

Strategy for seasonal prediction developments at ECMWF