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Extended range prediction of active-break spells of Indian summer monsoon rainfall using an ensemble prediction system in NCEP Climate Forecast System

Abhilash, S and Sahai, AK and Pattnaik, S and Goswami, BN and Kumar, A (2014) Extended range prediction of active-break spells of Indian summer monsoon rainfall using an ensemble prediction system in NCEP Climate Forecast System. International Journal of Climatology, 34 (1). pp. 98-113.

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Abstract

This study analyses skill of an extended range prediction system to forecast Indian Summer Monsoon Rainfall (ISMR) 3-4 pentads in advance. A series of 45-d forecast integrations starting from 1 May to 29 September at 5-d interval for 7 years from 2001 to 2007 are performed with an ensemble prediction system (EPS) in NCEP Climate Forecast System Version 1 (CFSV1) model. The sensitivity experiments with different amount of perturbation suggest that full tendency perturbation experiment on all basic variables including humidity at all vertical level shows higher dispersion among forecast than other experiments. Spread-error relationship shows that the present EPS system is under-dispersive. The lower bound of predictability is about 10-12 d and upper bound of predictability is found to be 20-25 d for zonal wind at 850 and 200 hPa. The signal-to-noise ratio (SNR) of precipitation (500 hPa geopotential height) reveals that the predictability limit is about 15(18) d over Indian monsoon region. The monsoon zone area averaged precipitation forecasts averaged over 5-d period (pentads) up to 4 pentad lead time are also evaluated and compared with observation. The anomaly correlation coefficients (ACC) reaches zero after pentad 3 (pentad 5) lead for precipitation (dynamical variables). A probabilistic approach is developed from the EPS for extended range forecast applications. The relative operating characteristic (ROC) curves for three categories of precipitation shows that the prediction skill for active and break is slightly higher compared to that of normal category and skillful probabilistic forecasts can be generated for precipitation even beyond pentad 4 lead.

Item Type: Article
Additional Information: Copyright of this article belong to Royal Meteorological Society.
Uncontrolled Keywords: Ensemble prediction systems; Extended range; Indian summer monsoon; Indian summer monsoon rainfall; Probabilistic approaches; Probabilistic forecasts; Relative operating characteristics; Signaltonoise ratio (SNR), Atmospheric thermodynamics; Experiments; Rain; Weather forecasting, Climate models, climate prediction; ensemble forecasting; monsoon; precipitation (climatology); probability; rainfall; signal-to-noise ratio; summer; weather forecasting
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 27 Nov 2014 10:02
Last Modified: 27 Nov 2014 10:02
URI: http://moeseprints.incois.gov.in/id/eprint/971

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