A new perspective on ENSO-Indian summer monsoon rainfall relationship in a warming environment
- PDF / 8,124,159 Bytes
- 20 Pages / 595.276 x 790.866 pts Page_size
- 41 Downloads / 196 Views
A new perspective on ENSO‑Indian summer monsoon rainfall relationship in a warming environment Pushpa Pandey1 · Suneet Dwivedi1 · B. N. Goswami2 · Fred Kucharski3 Received: 11 March 2020 / Accepted: 29 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract A robust estimate of the ENSO-Indian summer monsoon rainfall (ISMR) relationship in a changing climate is critically important for projection of the ISMR predictability. In this study, we show that the increasing nonlinear trend of ISMR and global sea surface temperatures (SST) associated with the trend of the global warming mode leads to a ‘long-term’ component to the ENSO-ISMR relationship together with a ‘short-range’ component associated with the ENSO mode. Using historical and projected simulations by some state-of-the-art CMIP5 models, we separate the global warming mode from other oscillatory modes including the ENSO mode through a combined empirical orthogonal function (CEOF) analysis, supported by a signal-to-noise maximizing EOF analysis. We find that the ‘short-term’ ENSO-ISMR relationship, represented by significant negative correlation between JJAS NINO3.4 SST and ISMR does not change appreciably with increase in green-house gas (GHG) forcing while the ‘long-term’ relationship changes from weak to significantly positive. We demonstrate that in a warming environment, the global warming mode must be taken into account together with the ‘natural’ ENSO mode in order to predict ISMR with confidence and emphasize that predictability of ISMR at any given time must be reassessed taking into account contributions from both short and long-term ENSO-ISMR relationships. Keywords Indian summer monsoon rainfall · ENSO · Teleconnections · Climatic change · CMIP5 models
1 Introduction The El Nino and Southern Oscillation (ENSO) phenomenon, the largest interannual climate signal in the tropics also happens to be the largest tropical modulator of the Indian summer monsoon rainfall (ISMR). ENSO provides the basis for seasonal predictability of the ISMR in particular, and seasonal climate in tropics in general (Shukla 1981, 1998). The Indian monsoon-ENSO relationship as measured Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00382-020-05452-7) contains supplementary material, which is available to authorized users. * Suneet Dwivedi [email protected] 1
K Banerjee Centre of Atmospheric and Ocean Studies and M N Saha Centre of Space Studies, University of Allahabad, Allahabad, UP 211002, India
2
Physics Department, Cotton University, Guwahati, India
3
The Abdus Salam International Centre for Theoretical Physics, Earth System Physics Section, Trieste, Italy
by a correlation between an index of ENSO (e.g. Nino3 or Nino3.4) and ISMR (Rassmuson and Carpenter 1983; Pant and Parthasarathy 1981) has shown considerable decadal/ multi-decadal variability over the past century (Krishnamurthy and Goswami 2000). Another important aspect of this relationship is that the basic negati
Data Loading...
