期刊
CLIMATE DYNAMICS
卷 32, 期 6, 页码 855-872出版社
SPRINGER
DOI: 10.1007/s00382-008-0447-x
关键词
Intraseasonal oscillation; Madden-Julian oscillation; Asian monsoon; Forecasting skill; Numerical modeling
资金
- National Science Foundation's [ATM-0531771]
- National Oceanic and Atmospheric Administration's Climate Prediction [GCO6-196]
- ECMWF [ERA-40]
- Div Atmospheric & Geospace Sciences
- Directorate For Geosciences [965610] Funding Source: National Science Foundation
The extended-range forecast skill of the ECMWF operational forecast model is evaluated during tropical intraseasonal oscillation (ISO) events in the Indo-West Pacific warm pool. The experiment consists of ensemble extended serial forecasts including winter and summer ISO cases. The forecasts are compared with the ERA-40 analyses. The analysis focuses on understanding the origin of forecast errors by studying the vertical structure of relevant dynamical and moist convective features associated with the ISO. The useful forecast time scale for circulation anomalies is in average 13 days during winter compared to 7-8 days during summer. The forecast skill is not stationary and presents evidence of a flow-dependent nature, with states of the coupled system corresponding to long-lived convective envelopes associated with the ISO for which the skill is always low regardless of the starting date of the forecast. The model is not able to forecast skillfully the generation of specific humidity anomalies and results indicate that the convective processes in the model are associated with the erosion of the ISO forecast skill in the model. Circulation-associated anomalies are forecast better than moist convective associated anomalies. The model tends to generate a more stable atmosphere, limiting the model's capability to reproduce deep convective events, resulting in smaller humidity and circulation anomalies in the forecasts compared to those in ERA-40.
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