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A self-organizing map-based ensemble forecast system for extended range prediction of active/break cycles of Indian summer monsoon

Borah, N and Sahai, AK and Chattopadhyay, R and Joseph, S and Abhilash, S and Goswami, BN (2013) A self-organizing map-based ensemble forecast system for extended range prediction of active/break cycles of Indian summer monsoon. Journal of Geophysical Research D: Atmospheres, 118 (16). pp. 9022-9034.

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The paper describes a probabilistic prediction scheme of the intraseasonal oscillation of Indian summer monsoon (ISM) in the extended range (ER, ~3-4weeks) using a self-organizing map (SOM)-based technique. SOM is used to derive a set of patterns through empirical model reduction. An ensemble method of forecast is then developed for these reduced modes based on the principle of analogue prediction. A total of 900 ensembles is created based on the variations of one of the parameters, like length of the observation sample, number of patterns, number of lags, and number of input variables, keeping the others constant. Deterministic correlation skill at fourth pentad lead (15-20 days) from the current model is 0.47 (for development period, 1951-1999) and 0.43 (for hindcast period, 2000-2011) over the monsoon zone of India. This method effectively takes care of the stochastic uncertainties associated with a deterministic prediction scheme and provides better guidance to the user community. A large part of the uncertainty in the model's prediction skill is related to the interannual variability of the prediction skill of the active-break spells. The model has problems in forecasting the unusually long active/break spells during the monsoon season, especially during September. Forecasts from certain initial conditions are less predictable than those from others. We describe some probable mechanisms from the literature for such problems in the model. This study will provide a benchmark to evaluate dynamical models' skills in predicting the ISM in ER time scale in future.

Item Type: Article
Additional Information: Copyrights of this article belongs to American Geophysical Union.
Uncontrolled Keywords: Deterministic correlations; Ensemble forecast systems; Indian summer monsoon; Initial conditions; Interannual variability; Intraseasonal oscillations; Probabilistic prediction; Stochastic uncertainties, Atmospheric thermodynamics; Conformal mapping, Forecasting, annual variation; climate oscillation; climate prediction; empirical analysis; ensemble forecasting; literature review; map; monsoon; numerical model; probability; seasonal variation; stochasticity; summer; timescale; uncertainty analysis, India
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 18 Jun 2014 11:43
Last Modified: 18 Jun 2014 11:43

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