Predictability of the tropospheric circulation in the southern hemisphere from CHFP models

Abstract

An assessment of the predictability and prediction skill of the tropospheric circulation in the Southern Hemisphere was done. The analysis is based on seasonal forecasts of geopotential heights at 200, 500 and 850 hPa, for austral summer and winter from 11 models participating in the Climate Historical Forecast Project. It is found that predictability (signal-to-variance ratio) and prediction skill (anomaly correlation) in the tropics is higher than in the extratropics and is also higher in summer than in winter. Both predictability and skill are higher at high than at low altitudes. Modest values of predictability and skill are found at polar latitudes in the Bellinghausen-Amundsen Seas. The analysis of the changes in predictability and prediction skill in ENSO events reveals that both are slightly higher in the El Niño-Southern Oscillation (ENSO) years than in all years, while the spatial patterns of maxima and minima remain unchanged. Changes in signal-to-noise ratio observed are mainly due to signal changes rather than changes in noise. Composites of geopotential heights anomalies for El Niño and La Niña years are in agreement with observations.