Publication Date:
2014-10-25
Description:
The position and orientation of the South Pacific Convergence Zone (SPCZ), modulated by the El Niño-Southern Oscillation (ENSO) determines many of the potentially predictable interannual variations in rainfall in the South Pacific region. In this study, the predictability of the SPCZ in austral summer is assessed using two coupled ocean-atmosphere global circulation model (CGCM) based seasonal prediction systems: the Japan Meteorological Agency's JMA/MRI-CGCM; and the Australian Bureau of Meteorology's Predictive Ocean-Atmosphere Model for Australia (POAMA-M24). Forecasts of austral summer rainfall, initialised in November are assessed over the period 1980–2010. The climatology of CGCM precipitation in the SPCZ region compares favourably to rainfall analyses over subsets of years characterizing different phases of ENSO. While the CGCMs display biases in the mean SPCZ latitudes, they reproduce inter-annual variability in austral summer SPCZ position indices for forecasts out to four months, with temporal correlations greater than 0.6. The summer latitude of the western branch of the SPCZ is predictable with correlations of the order of 0.6 for forecasts initialised as early as September, while the correlation for the eastern branch only exceeds 0.6 for forecasts initialised in November. Encouragingly, the models are able to simulate the large displacement of the SPCZ during zonal SPCZ years 1982–83, 1991–92 and 1997–98.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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