Y. Fujii1, S. Matsumoto1, T. Yasuda1, M. Kamachi1, K. Ando2

（ 1MRI/JMA, 2JAMSTEC ）　

OSE Experiments Using the JMA-MRI ENSO Forecasting System

2nd GODAE OSE Workshop, Jun. 5th, Toulouse, France

Outline

1. Introduction

2. Experimental Design

3. Impacts of TAO/TRITON and Argo on the assimilation

4. Impacts of TAO/TRITON and Argo on the forecast

5. Impacts of satellite altimetry

6. Summary

1. Introduction

Increase of observed profiles with ARGO floats

Jan. 2000

Jan. 2006

ARGO

TAO/TRITON

Others (XBT, CTD)

The number of the observed points by Argo floats around the equator gets grater than that of TAO-TRITON Buoy.

Background of this study

・ Is TRITON really valuable for JMA’s operational ENSO Forecasting System?

・ Is it really necessary to sustain both TRITON and Argo Networks? (It may be oversampling.)

Questions

JAMSTEC would like to reduce the budget for TRITON.(They want to assign more budgets to Ocean bottom drilling, climate modeling research with Earth Simulator, and so on.)

Check the impacts of TAO/TRITON and Argo Networks (and satellite altimetry) on the JMA’s ENSO forecast system.

Joint Research of JAMSTEC and MRI

2. Experimental design

JRA25/JCDAS

JMA/MRI-CGCM

MOVE/MRI.COM-G

Observation

Observation

Outline of ENSO Forecasting in JMA

Initial State

Prediction

Atmospheric Data Assimilation System

Ocean Data Assimilation System

Coupled Atmosphere-Ocean GCM

・ Resolution: Atmosphere: TL95L40 Ocean: 0.3-1ºx1º, L50・ Coupling Interval: 1 hour・ Heat and momentum flux correction

Outline of the experiments

Assimilation （ MOVE/MRI.COM-G) → Jan. 2000-Dec. 2007

・ ALL → Using all available data (TAO/TRITON→10-day mean)

・ NTT → excluding the data of TAO/TRITON

・ NAF → excluding the data of ARGO floats

・ NSH → excluding satellite altimetry dataForecast （ JMA/MRI-CGCM) → 2004-2007 　（ 16 cases ）

・ Initial date ： Jan. 1st, Apr. 26th, Jul. 30th, Oct. 28th （ 4 times a year)

・ 13-month forecasts using 11 ensemble members are performed　　　　　 for ALL, NTT, NAF, and NSH individually.

　　　・ Ensembles → Assimilation runs with perturbed SST Obs.

　　　・ The same flux correction as in the JMA operation is used.

　　　・ Forecasts biases are calculated for each lead time, each forecasted month, and each experiments (ALL, NTT, NAF, NSH) individually, and removed from the forecasted fields.

3. Impact of TAO/TRITON and Argo Floats on Assimilated fields

Variation of the impact on Z20 in the EQ PAC

ｍ ｍ

Averaged T difference in the eq. Pac. (2004-07)

゜C

゜C

ALL-NTT ALL-NAF

Contours represents temperature fields in ALL.

TAO/TRITON has an impact different from Argo(!?)

4. Impact of TAO/TRITON and Argo Floats on ENSO Forecasting

Impact on 0-6 month forecast

RMSE Improvement ratio = RMSE of NTT or NAF – RMSE of ALL

RMSE of ALL

Impact on 7-12 month forecast

・ The impact is large in the Indian Ocean for 7-12 month forecast

・ Impact of Argo can be seen on the equatorial and western tropical Pacific.

Impact on 0-6 month forecast score

Significance

NTT ５０％ ９３％ ９６％ ９７％ ４７％ ５３％ ３５％NAF ６２％ ８９％ ７６％ ８０％ ７９％ ５７％ ６２％

Normarized RMSE (0-6month)

0.4

0.45

0.5

0.55

0.6

0.65

0.7

0.75

0.8

0.85

0.9

NINO12 NINO3 NINO34 NINO4 NINO-W STIO WTIO

RM

SE

ALLNTTNAF

Significance

NTT ５０％ ９３％ ９６％ ９７％ ４７％ ５３％ ３５％NAF ６２％ ８９％ ７６％ ８０％ ７９％ ５７％ ６２％

Normarized RMSE (0-6month)

0.4

0.45

0.5

0.55

0.6

0.65

0.7

0.75

0.8

0.85

0.9

NINO12 NINO3 NINO34 NINO4 NINO-W STIO WTIO

RM

SE

ALLNTTNAF

Normalized RMSE by that of the persistency forecast

Balmaseda, M. A., and D. Anderson (2008b) Impact on initialization strategies and observations on seasonal forecast skill. Geophys. Res. Lett., submitted.

Comparison with ECMWF

ECMWF

0-6 month AME improved ratio

-10%

-5%

0%

5%

10%

15%

20%

25%

NINO12 NINO3 NINO34 NINO4 NINO-W STIO WTIO

NAFNTT

JMA

AME: Absolute Mean Error

Changes of Spread from ALL

0-12 Spred Change-Ratio

-8%

-6%

-4%

-2%

0%

2%

4%

6%

8%

NINO12 NINO3 NINO34 NINO4 NINO-W STIO WTIO

NTTNAFNSH

・ Spreads tends to increase without TAO/TRITON data.

・ Spreads tends to decrease without Argo floats.

?

Example of forecasts

Initial: 20051028

Initial: 20070730

6. Summary

Summary

TAO/TRITON Array

・ Remarkable positive impact on NINO3 and NINO4 areas for 0-6 month SST forecast.

・ The Impact is not clear on western tropical Pacific and for 7-12 month forecast.

Argo Floats

・ Positive impact on NINO3, NINO4, western tropical Pacific, and Western Indian Ocean for 0-6 month forecast.

・ The positive impact remains for 7-12 month forecasts.

Things to Note

・ Results of OSE depends on the model, and data assimilation scheme.

OSE should be performed with multi systems

・ We use 10-day mean observation data. The effect of the high time-resolution of TAO/TRITON is not evaluated.

・ Atmospheric reanalysis used in the data assimilation run already uses information from TAO/TRITON.

・ A longer time period is required for evaluating the impacts of TAO/TRITON and Argo floats correctly.

(A better system in the future may use data more effectively for improving forecast. It is dangerous to judge the importance only with state of art systems.)

Thank You