Predictability and Prediction of Tropical Intra-Seasonal Oscillation (TISO) Xiouhua (Joshua) Fu Collaborators:

Predictability and Prediction of
Tropical Intra-Seasonal Oscillation (TISO)
Xiouhua (Joshua) Fu
International Pacific Research Center (IPRC)
University of Hawaii at Manoa, Honolulu, Hawaii
Collaborators:
Bin Wang, Bo Yang, Qing Bao
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Global Impacts of TISO
Boreal-summer ISO
The TISO
Eastward
Boreal-winter MJO
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Intra-Seasonal Variability
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Air-sea Coupling Extends the Predictability of TISO
ATM Forecast Error
Signal
CPL Forecast Error
[ATM: 17 days; CPL: 24 days]
Fu and Wang et al. 2007, JAS
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Air-Sea Coupling Processes

+
Wang and Xie (1998)
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Specific Questions to be Addressed
 How will different surface boundary conditions (five
different SST settings) affect the TISO predictability
(with “perfect” model assumption)? What are the best
SST configurations for TISO hindcasts and
operational forecasts?
 What is the “practical” predictability of TISO in a
dynamical model (IPRC_HcGCM)?
Fu et al. (2007), MWR, In press
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
IPRC/UH Hybrid coupled GCM
(IPRC_HcGCM)
 Atmospheric component:
ECHAM-4 T30L19 AGCM
(Roeckner et al. 1996)
 Ocean component:
Wang-Li-Fu intermediate upper ocean model (0.5ox0.5o)
(Wang et al. 1995; Fu and Wang 2001)
 Wang, Li, and Chang (1995): upper-ocean thermodynamics
 McCreary and Yu (1992): upper-ocean dynamics
 Jin (1997) : mean and ENSO (intermediate fully coupled model)
 Zebiak and Cane (1987): ENSO (intermediate anomaly coupled model)
 Fully coupling without heat flux correction
 Coupling region: Tropical Indian and Pacific Oceans (30oS-30oN)
 Coupling interval: Once per day
Fu et al. 2003; Fu and Wang 2004 (TISO)
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Ensemble Experiments
With Five Different SST Settings
Experiment
Name
SSTs Used in 90-day Forecasts
CPL
SST directly forecasted by interactive air-sea coupling
(Tier-one)
ATM
Daily SST from the coupled control run after removing
20-90-day variability ( “smoothed” SST)
ATMp
Daily SST from the coupled control run is linearly
interpolated to the “smoothed” SST within first 10-day
forecast (damped persistent SST)
ATMf
Daily SST anomaly from coupling to a slab mixed-layer
ocean (ML depth = 30 m) is added to the “smoothed” SST
ATMd
Ensemble-mean daily SST from the CPL forecasts
(Tier-two)
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Experimental Design
 2 TISO events (boreal-summer) in a coupled control run
(Targets)
 4 phases for each TISO event (Starting points)
 10 ensemble forecasts starting from each phase
of selected events under five different SST settings
(80 forecasts per SST setting)
Data Processing
 TISO: 20-90-day filtered daily rainfall
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Event-I
Event-II
Targets
Coupled Forecasts
(CPL)
Ten-ensemble-mean
Atmosphere-only
Forecasts (ATM)
Boreal-summer Rainfall over (65oE-120oE)
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
TISO Predictability Measured by ACC
ACC
(Tier-1/Tier-2)
Ensemble means
ATM/ATMp: 30 days
CPL/ATMd: 42 days
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
TISO Forecast Experiments with IPRC_HcGCM
An MJO event observed during TOGA-COARE
1993, Jan. 01-Feb. 10 (boreal-winter)
A monsoon ISO event
2006, Jun. 11-Jul. 11 (boreal-summer)
 Initialized with NCEP reanalysis
 100-ensemble forecasts for each event
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
MJO Events Observed during TOGA-COARE
1992
1993
VP-200
U-850
OLR
Vitart et al. (2007)
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
MJO Forecasted by ECMWF Operational
Seasonal Forecast System
Dec. 31,1992
Feb. 1,1993
VP-200
Vitart et al. (2007)
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
MJO Forecasted by the IPRC_HcGCM
Rainfall
Observation
With default
cumulus scheme
With revised
cumulus scheme
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
MJO Forecasted by the IPRC_HcGCM
OLR
(U850 U200)
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Atmosphere-only Forecast
With revised cumulus scheme
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
An Experimental Forecast of Monsoon ISO
Boreal-summer Rainfall over (65oE-120oE)
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Summary
 The TISO predictability in IPRC/UH_HcGCM reaches
about 40 days averaged over the Southeast Asia. The
predictability in the atmosphere-only model is about 30
days. Interactive air-sea coupling extends the TISO
predictability by about 10 days.
 Tier-two system could reach similar TISO predictability
as tier-one system, suggesting that using observed
high-frequency SST for TISO hindcasts and using
interactive air-sea coupling and forecasted daily SST for
real-time forecasts are good options.
 The optimistic side of this TISO forecast experiment
suggests that some current dynamical models are ready
to carry out intraseasonal forecast and will provide
useful information for extended weather forecast.
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Thanks
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Air-sea coupling enhances the northward
propagating monsoon ISO (IPRC_HcGCM)
Fu et al. 2003, Fu and Wang 2004
(65oE-95oE)
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Coupling also extends the predictability of weather
ATM Forecast Error
Signal
CPL Forecast Error
ATM/(Negative): 8 days
(During break-to-active transition)
CPL/(Positive): 16 days
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Two Methods to Measure the Predictability
Ratio of Signal- to- Forecast Error
Forecast Time
Anomaly Correlation Coefficient (ACC)
1.0
0.5
Forecast Time
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Wheeler-Hendon Phase-space MJO Diagram
PC-2
PC-2
PC-1
PC-1
Model
Observation
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Filtered rainfall over (80oE–100oE, 5oS-5oN)
Phase 3
Phase 2
Phase 4
Fu et al. 2006, JAS
Phase 1
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
TISO Predictability Measured by Signal-to-Error Ratio
ATM Forecast Error
CPL Forecast Error
Signal
Individual ensembles
ATM/ATMp: 24 days
CPL/ATMd: 34 days
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
TISO Predictability Measured by ACC
ACC
ATM/ATMp: 21 days
CPL/ATMd: 30 days
Individual ensembles
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
MJO Forecasted by the IPRC_HcGCM
OBS
Revised
Default
Atmosphere
only
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
Signal-to-Error Method
Control run
Perturbed Forecasts
(Signal) L=25 days for TISO
(Forecast Error)
Waliser et al. (2003)
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007
SSTs in Five Experiments
Control
Mixed-layer
“Smoothed”
Coupled/Daily
Damped persistent
NOAA 32nd CDPW, Tallahassee, Oct 22-26, 2007