Seasonal Prediction

Tropical climate variations such as El Nino/Southern Oscillation (ENSO) and ENSO Modoki in the tropical Pacific and the Indian Ocean Dipole Mode (IOD) have enormous impacts on the global climate and the human societies. Therefore, there is a significant benefit to our societies if these climate events are predicted sufficiently ahead of their occurrences. Since the mid-1980s, many research institutes and operational centers have developed various numerical prediction models for ENSO forecast. Also, the IOD and ENSO Modoki predictions are attempted by some of the leading modeling groups recently.

The numerical prediction of weather has been proven to be very useful to us now days because of the superb advancements made in that area of research during last several decades. Such weather forecast systems mostly employ standalone atmospheric models on the assumption that the oceans do not change in the relatively short prediction period (~1 week). However, such standalone atmospheric models are not ideal for predictions of climate phenomena like ENSO, ENSO Modoki and IOD that strongly depend on the ocean-atmosphere interactions. Application of ocean-atmosphere coupled model is naturally a proven approach to overcome the shortcoming of the standalone atmospheric model and to realistically simulate the climate phenomena.

For our climate predictions, we have developed the SINTEX-F1 ocean-atmosphere coupled general circulation model under the EU-Japan research collaboration. Based on this seasonal prediction system ("F1"), we have performed climate predictions at least 1 year ahead and distributed the prediction information on JAMSTEC website since 2005 (LINK). We have achieved great successes in these years and SINTEX-F1 has become one of the leading models of the world for predicting the tropical climate variations in particular the IOD, the ENSO and the ENSO Modoki. (publications)

To improve prediction of extratropical climate, a upgraded CGCM called SINTEX-F2 has been developed; the new system is a high-resolution version with a dynamical sea-ice model ("F2"). For the tropical climate variations in the Pacific and the Indian Ocean, the SINTEX-F2 preserves the high-prediction skill, and sometimes even shows higher skill especially for strong events, as compared to the SINTEX-F1. In addition, it has turned out that the new system is more skillful in predicting the subtropics, particularly, the Indian Ocean Subtropical Dipole and the Ningaloo Niño.

We provide some unique forecast based on some scientific evidences
 2-yr ENSO and ENSO-Modoki forecast (only by "F2-3DVAR")
   (Luo et al. (2008) and Behera et al. (2020))
 Coastal Nino/Nina and Subtropical Dipole Mode forecast
   (Doi et al. (2013),Doi et al. (2015),Yuan et al. (2014),Doi et al. (2016))
 Sea level anomaly (real-time forecast in preparation)
   (Doi et al. (2020))

The SINTEX-F1/F2 seasonal prediction systems adopts a relatively simple initialization scheme based on nudging only the sea surface temperature (SST). However, it is to be expected that the system is not sufficient to capture in detail the subsurface oceanic precondition. Therefore, we have introduced a new three-dimensional variational ocean data assimilation (3DVAR) method that takes three-dimensional observed ocean temperature and salinity into account. This system ("F2-3DVAR") has successfully improved seasonal predictions in the tropical Indian and Atlantic Ocean. In addtion, we have developed "F2si" system, which adopts Sea ice concentration (SIC) as well as SST nudging scheme for the initialization

"All" shows mean of 36 ensemble members of the three system of "F2", "F2-3DVAR", and "F2si".

The 12-member F2-3DVAR system is recently upgraded to increase the ensemble size to 108-members "108mem"


SINTEX-F1 system (Luo et al. 2005)

We adopt the SINTEX-F1 atmosphere-ocean coupled general circulation model, which was developed under the European Union-Japan research collaboration. The SINTEX-F1 consists of the atmospheric component ECHAM4 and the ocean component OPA8. The ECHAM4 has the horizontal resolution of T106 (~100km) with 19 vertical levels. The OPA8 has the resolution of 2° Mercator mesh (enhanced to 0.5° in the latitudinal direction near the equator) with 31 vertical levels. The atmosphere and ocean components in the model interact every 2 hours via OASIS2 coupler without any flux corrections.
Since atmosphere-ocean coupled system involves the strong nonlinearity, variations in initial conditions and physical schemes lead to diverse solutions. Therefore, as is customary now, we employ many ensemble members to reduce the prediction uncertainties associated with different initial conditions and physical schemes. For creating ensemble members based on initial conditions in our prediction system, model sea surface temperature is nudged toward observed sea surface temperatures by three different negative feedback values to the surface heat flux. In addition, three different atmosphere-ocean coupling schemes are employed to represent other ensemble members. Through this processes, in total 9 ensemble members are employed for our seasonal to interannual climate predictions initiated every month.
Luo, J.-J., S. Masson, S. Behera, S. Shingu, and T. Yamagata (2005), Seasonal climate predictability in a coupled OAGCM using a different approach for ensemble forecasts, J. Clim., 18, 4474–4494

SINTEX-F2 system (Doi et al. 2016)

The SINTEX-F2 coupled model has been developed for better representation of several physical processes and to resolve relatively small-scale phenomena in the ocean. The atmospheric component, ECHAM5, has a horizontal resolution of 1.125° (T106) with 31 vertical levels. The horizontal grid used for the oceanic component, OPA9, is on the ORCA05 configuration, which has a horizontal resolution of about 0.5° × 0.5° with 31 vertical levels and without any further refinement over the tropics. The Louvain-la-Neuve Sea Ice Model, version 2 (LIM2) is embedded.
As similar to the SINTEX-F1 system, the SST-nudging semicoupled initialization scheme is adopted; model SSTs are strongly nudged toward observations by applying three large negative feedback values to the surface heat flux. We used two kinds of daily SST observational dates; one is interpolated from the weekly OISSTv2 data with 1.0° latitude × 1.0° longitude global grid, and the other is the high-resolution daily NOAA OISST analysis with 0.25° latitude × 0.25° longitude global grid. In addition, considering large uncertainties in ocean vertical mixing estimations, ocean physics is perturbed in two different ways for the ocean vertical mixing induced by small vertical scale structures within and above the equatorial thermocline.
Doi, T., S. K. Behera, and T. Yamagata (2016), Improved seasonal prediction using the SINTEX-F2 coupled model, J. Adv. Model. Earth Syst., 8, 1847-1867, doi:10.1002/2016MS000744.

SINTEX-F2-3DVAR system (Doi et al. 2017)

This system is a upgrade version of the SINTEX-F2 ystem in terms of the ocean initialization. In this system, OGCM SSTs are strongly nudged toward the observations in the coupled run continuously from January 1982, which is similar to the simple SST-nudging scheme used in the F2-system. In addition, 3DVAR correction is conducted every 1st day of each month using subsurface ocean temperature and salinity observation. The set of in situ observations consists of all types of ocean profiling instruments that provide temperature and salinity (when available) from the expandable bathythermographs (XBTs), mooring buoys, sea stations, Argo floats, etc. The details of the 3DVAR scheme used here such as formulation and specification of observation and background error covariances are shown in Storto et al. (2014)
Doi, T., A. Storto, S. K. Behera, A. Navarra, and T. Yamagata (2017), Improved prediction of the Indian Ocean Dipole Mode by use of subsurface ocean observations. Journal of Climate, 30, 7953-7970.
Storto, A., Masina, S. and Dobricic, S., 2014: Estimation and Impact of Non-Uniform Horizontal Correlation Length-Scales for Global Ocean Physical Analyses. Journal of Atmospheric ad Ocean Technology. 31, 2330-2349.

SINTEX-F2-3DVAR 108-members ensemble system (Doi et al. 2019)

The 12-member F2-3DVAR system is recently upgraded to increase the ensemble size to 108-members using the Lagged Average Forecasting (LAF) method. Based on this new system, we have conducted the prediction runs with a four-month lead-time from the eight initialized dates (1st-9th) of each month during the period from 1983 to 2019 (6-month lead time forecast is also available from some key months).
Doi, T., S. K. Behera, and T. Yamagata (2019), Merits of a 108-Member Ensemble System in ENSO and IOD Predictions. J. Climate, 32, 957–972,

SINTEX-F Family ( F1 + F2 + F2-3DVAR) system (Doi et al. 2020)

Doi, T., S. K. Behera, and T. Yamagata, 2020: Predictability of the Super IOD Event in 2019 and Its Link With El Niño Modoki.Geophysical Research Letters, 47, e2019GL086713.

SINTEX-F2si system (Morioka et al. 2019)

This system is a upgrade version of the SINTEX-F2 system in terms of the sea ice initialization. In this system, SST and SIC are strongly nudged toward the observations in the coupled run continuously from January 1982.
Morioka, Y., T. Doi, D. Iovino, S. Masina, and S. K. Behera, 2019: Role of sea-ice initialization in climate predictability over the Weddell Sea. Scientific Reports, 9, Article number: 2457