Forecast of Tropical Pacific SST using an intermediate ocean and a statistical atmosphere model

Contributed by In-Sik Kang¹, Chung-Kyu Park², and Jong-Seong Kug¹

¹School of Earth and Environment Sciences, Seoul National University, Seoul 151-742, Korea

²Korea Meteorological Administration, Seoul 156-720, Korea

El Nino prediction for Sep. 2000 - Aug 2001 has made using the KMA/SNU ENSO prediction system (Kang and Kug, 2000). The system is based on the intermediate ocean and statistical atmosphere model. The ocean model differs from the Cane and Zebiak (1987) model in the parameterization of subsurface temperature and the basic state. The statistical atmosphere model is developed based on the singular value decomposition (SVD) of wind stress and SST. The initialization of the model is done by combining observed SST and wind stress. Wind stress is calculated by using 925hPa wind of NCEP/NCAR reanalysis data. Using calculated wind stress for initialization has better forecast skill than the case of FSU wind stress in recent prediction. (Kug et al., 2000). In addition, the present prediction is attended with random noise to consider weather noise and to generate many sets of prediction. Our approach for random noise is similar to Kirtman and Schopf (1998).

Figure 1 shows the Nino3 SST forecast with 12 month lead, with random noise (thin solid lines) and their ensemble mean (thick solid line) of 20 forecasts. The forecasts indicate that the Nino3 SST persists normal state till next spring. Figure 2 shows seasonal SST forecast in tropical Pacific basin for Dec. 2000 - Nov. 2001. Forecast result indicates that negative SST anomalies in the central Pacific slowly decay.

Reference

Cane, M. A., S. E. Zebiak, 1987: Prediction of El Nino events using a physical model, In Atmospheric and Oceanic Variability, H. Cattle, Ed., Royal Meteorological Society press, 153-182

Kang, I.-S. and J.-S. Kug, 2000: An El-Nino prediction system with an intermediate ocean and statistical atmosphere model, Geophys. Res. Lett. 27, 1167-1170.

Kug, J.-S., I.-S. Kang and S. E. Zebiak 2000: Impacts of different wind stress data in the initialization of an intermediate ocean model and the ENSO predictability, In preparing

Kirtman, B. P. and P. S. Schopf, 1998: Decadal variability in ENSO predictability an prediction, J. Climate, 11, 2804-2822.