Unraveling the Mystery of Indian Summer Monsoon Prediction: Improved Estimate of Predictability Limit. Issue 4 (19th February 2019)

• Record Type: Journal Article
• Authors: Saha, Subodh Kumar; Hazra, Anupam; Pokhrel, Samir; Chaudhari, Hemantkumar S.; Sujith, K.; Rai, Archana; Rahaman, Hasibur; Goswami, B. N.
• Is Part Of: Journal of geophysical research. Volume 124:Issue 4(2019)
• Page Start: 1962
• Page End: 1974
• Publication Date: 2019-02-19
• Subjects: Indian summer monsoon -- prediction -- climate modeling; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2018JD030082
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Large socioeconomic impact of the Indian summer monsoon (ISM) extremes motivated numerous attempts at its long range prediction over the past century. However, a rather low potential predictability (PP) of the seasonal ISM, contributed significantly by "internal, " interannual variability was considered insurmountable. Here we show that the internal variability contributed by the ISM subseasonal (synoptic + intraseasonal) fluctuations, so far considered chaotic, is partly predictable as found to be tied to slowly varying forcing (e.g., El Niño and Southern Oscillation). This provides a scientific basis for predictability of the ISM rainfall beyond the conventional estimates of PP. We establish a much higher actual limit of PP ( r ∼0.82) through an extensive reforecast experiment (1, 920 years of simulation) by improving two major physics in a global coupled climate model, which raises a hope for a very reliable dynamical seasonal ISM forecasting in the near future. Key Points: The observed link between synoptic variability and predictable modes suggest a high predictability of the ISMR CFSv2 with improved physics shows ISMR prediction skill higher than current estimate of potential predictability Model shows ∼70% of interannual variability of ISMR is predictable, which is much higher than earlier estimates (∼45%)