Vol.:(0123456789) 1 3 Climate Dynamics https://doi.org/10.1007/s00382-019-05085-5 Interdecadal modulation of the Indo‑western Pacifc Ocean Capacitor mode and its infuence on Indian summer monsoon rainfall Patekar Darshana 1,2  · Jasti S. Chowdary 1  · C. Gnanaseelan 1  · Anant Parekh 1  · G. Srinivas 3 Received: 2 August 2019 / Accepted: 7 December 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract The present study investigates the interdecadal modulations of interannual variability in the Indo-western Pacifc Ocean Capacitor (IPOC) mode and its infuence on the Indian summer monsoon (ISM) rainfall during 1886–2014. The IPOC mode is extracted using singular value decomposition (SVD) analysis of tropical Indian Ocean (TIO) sea surface temperature (SST) and western North Pacifc (WNP) 850 hPa relative vorticity anomalies during the boreal summer season (June to August; JJA). Analysis suggests that the IPOC mode induces a southwest-northeast dipole pattern in the Indian subcontinent rainfall with signifcant positive anomalies over the southern peninsular India and negative anomalies over the eastern parts of the Indo-Gangetic plains during the positive phase of IPOC. The 21-year sliding correlation coefcients between rainfall dipole index and leading principal component of SVD analysis (SVD-PC1) suggest that IPOC and ISM rainfall relationship exhibits signifcant interdecadal variability during the study period. The entire period has been divided into three distinct epochs as 1895–1926 (epoch-1), 1932–1972 (epoch-2) and 1976–2007 (epoch-3) based on 21-year sliding correlation. It is found that the IPOC mode strongly afect ISM rainfall in epoch-1 and epoch-3, whereas this relationship between the IPOC mode and ISM rainfall is inadequate in epoch-2 pertaining to the absence of the dipole rainfall pattern. The mechanisms responsible for such epochal changes in relationship between IPOC mode and ISM rainfall are discussed. In epoch-1 and epoch-3, anomalous TIO SST and the Pacifc–Japan (PJ) pattern/WNP circulation both are well organized as part of the IPOC mode. However, in epoch-2 vigorous warm SSTs over the equatorial central Pacifc and cyclonic circulation over the north Pacifc accompanied by SST cooling around 40°N are noticed. The north Pacifc cyclonic circulation accelerates the southwesterlies emerging from north-western fank of WNP anticyclone. On the other hand, positive SST anomalies and associated low-level convergence in central equatorial Pacifc limit the extension of northeasterlies from the southern edge of WNP anticyclone to TIO. As a result, WNP anticyclone is squeezed/twisted between them, thereby weakening and shift- ing it northeastward. This in turn weakens the PJ mode and the inter-basin interaction of WNP circulation and TIO SSTs, causing disorganized IPOC pattern in epoch-2. Keywords Western North Pacifc · Indian summer monsoon · Tropical Indian Ocean · Pacifc–Japan pattern · El Niño Southern Oscillation 1 Introduction The Indian summer monsoon (ISM) is one of the major components of Asian summer monsoon. In the period from June to September, the cross equatorial fow through Ara- bian Sea brings moisture towards Indian landmass. Densely populated Indian subcontinent get 80% of its annual pre- cipitation in this season (Gadgil and Gadgil 2006). India’s agricultural productivity and socio-economic infrastructure highly depend on the stability, variability and extremes of ISM rainfall (e.g., Webster et al. 1998; Gadgil and Gadgil 2006; Wang 2006). Therefore, ISM rainfall prediction is * Jasti S. Chowdary jasti@tropmet.res.in 1 Indian Institute of Tropical Meteorology, Pune 411008, India 2 Savitribai Phule Pune University, Pune 411007, India 3 Indian National Centre for Ocean Information Services, Hyderabad 500090, India