Seasonal Forecasting with a Simple General Circulation Model: Predictive Skill in the AO and PNA

A primitive equation dry atmospheric model is used to perform ensemble seasonal predictions. The predictions are done for 51 winter seasons [December–January–February (DJF)] from 1948 to 1998. Ensembles of 24 forecasts are produced, with initial conditions of 1 December plus small perturbations. The...

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Bibliographic Details
Published in:Journal of climate 2005-02, Vol.18 (4), p.597-609
Main Authors: Derome, Jacques, Lin, Hai, Brunet, Gilbert
Format: Article
Language:English
Subjects:
Atmospheric circulation
Atmospheric models
Atmospheric research
Atmospherics
Climate change
Climate models
Climatology
Earth, ocean, space
El Nino
Exact sciences and technology
External geophysics
Forecasting models
Meteorology
Modeling
Time series forecasting
Weather analysis and prediction
Weather forecasting
Winter
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Summary:A primitive equation dry atmospheric model is used to perform ensemble seasonal predictions. The predictions are done for 51 winter seasons [December–January–February (DJF)] from 1948 to 1998. Ensembles of 24 forecasts are produced, with initial conditions of 1 December plus small perturbations. The model uses a forcing field that is calculated empirically from the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalyses. The forcing used to forecast a given winter is the sum of its winter climatological forcing plus an anomaly. The anomalous forcing is obtained as that of the month prior to the start of the forecast (November), which is also calculated from NCEP data. The predictions are thus made without using any information about the season to be predicted. The ensemble-mean predictions for the 51 winters are verified against the NCEP–NCAR reanalyses. Comparisons are made with the results obtained with a full GCM. It is found that the skill of the simple GCM is comparable in many ways to that of the full GCM. The skill in predicting the amplitude of the main patterns of Northern Hemisphere mean-seasonal variability, the Arctic Oscillation (AO) and the Pacific–North American (PNA) pattern is also discussed. The simple GCM has skill not only in predicting the PNA pattern during winters with strong ENSO forcing, but it also has skill in predicting the AO in winters without appreciable ENSO forcing.
ISSN:0894-8755
1520-0442
DOI:10.1175/JCLI-3289.1