New spatial and temporal indices of Indian summer monsoon rainfall
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The overall yearly seasonal performance of Indian southwest monsoon rainfall (ISMR) for the whole Indian land mass is presently expressed by the India Meteorological Department (IMD) by a single number, the total quantum of rainfall. Any particular year is declared as excess/deficit or normal monsoon rainfall year on the basis of this single number. It is well known that monsoon rainfall also has high interannual variability in spatial and temporal scales. To account for these aspects in ISMR, we propose two new spatial and temporal indices. These indices have been calculated using the 115 years of IMD daily 0.25° × 0.25° gridded rainfall data. Both indices seem to go in tandem with the in vogue seasonal quantum index. The anomaly analysis indicates that the indices during excess monsoon years behave randomly, while for deficit monsoon years the phase of all the three indices is the same. Evaluation of these indices is also studied with respect to the existing dynamical indices based on large-scale circulation. It is found that the new temporal indices have better link with circulation indices as compared to the new spatial indices. El Nino and Southern Oscillation (ENSO) especially over the equatorial Pacific Ocean still have the largest influence in both the new indices. However, temporal indices have much better remote influence as compared to that of spatial indices. Linkages over the Indian Ocean regions are very different in both the spatial and temporal indices. Continuous wavelet transform (CWT) analysis indicates that the complete spectrum of oscillation of the QI is shared in the lower oscillation band by the spatial index and in the higher oscillation band by the temporal index. These new indices may give some extra dimension to study Indian summer monsoon variability.
The authors are thankful to anonymous reviewers for providing valuable suggestions to improve the quality of the manuscript. The authors thank the India Meteorological Department (IMD) for providing the gridded rainfall data. The authors wish to acknowledge the use of the Ferret program for analysis and graphics in this paper. Ferret is a product of NOAA’s Pacific Marine Environmental Laboratory. (Information is available at http://ferret.pmel.noaa.gov/Ferret/).
The first author is thankful to Science and Engineering Research Board (SERB), Department of Science & Technology (DST), Government of India for providing necessary partial funds to carry out this work through PDF/2016/003854, National Atmospheric Research Laboratory (NARL) and Indian Space Research Organization (ISRO) for providing necessary support.
- Dee DP, Uppala SM, Simmons AJ, Berrisford P, Poli P, Kobayashi S, Andrae U, Balmaseda MA, Balsamo G, Bauer P, Bechtold P, Beljaars ACM, van de Berg L, Bidlot J, Bormann N, Delsol C, Dragani R, Fuentes M, Geer AJ, Haimberger L, Healy SB, Hersbach H, Hólm EV, Isaksen L, Kållberg P, Köhler M, Matricardi M, McNally AP, Monge-Sanz BM, Morcrette J-J, Park BK, Peubey C, de Rosnay P, Tavolato C, Thépaut JN, Vitart F (2011) The ERA-interim reanalysis: configuration and performance of the data assimilation system. Q J R Meteorol Soc 137:553–597CrossRefGoogle Scholar
- Gadgil S, Rajeevan M, Nanjundiah R (2005) Monsoon prediction—why yet another failure? Curr Sci 88:1389–1400Google Scholar
- Gadgil S, Rajeevan M, Francis PA (2007) Monsoon variability: links to major oscillations over the equatorial Pacific and Indian oceans. Curr Sci 93:182–194Google Scholar
- IMD (2002) Southwest Monsoon end of season report, 2002, available at http:/www.imd.gov.in
- IMD (2004) Southwest Monsoon end of season report, 2004, available at http:/www.imd.gov.in
- IMD (2009) Southwest Monsoon end of season report, 2009, available at http:/www.imd.gov.in
- IMD (2014) Southwest Monsoon end of season report, 2014, available at http:/www.imd.gov.in
- IMD (2015) Southwest Monsoon end of season report, 2015, available at http:/www.imd.gov.in
- Parthasarathy B, Rupa Kumar K, Kothawale DR (1992) Indian summer monsoon rainfall indices: 1871±1990. Meteorol Mag 121:174–186Google Scholar
- Rajeevan M, Bhate J, Kale JD, Lal B (2006a) High resolution daily gridded rainfall data for Indian region: analysis of break and active monsoon spells. Curr Sci 9(3):296–306Google Scholar
- Rajeevan M, Pai DS, Anil Kumar R, Lal B (2006b) New statistical models for long-range forecasting of southwest monsoon rainfall over India. Clim Dyn. https://doi.org/10.1007/s00382-006-019706
- Saji NH, Goswami BN, Vinayachandran PN, Yamagata T (1999) A dipole mode in the tropical Indian Ocean. Nature 401:360–363Google Scholar
- Sikka DR (1980) Some aspects of the large-scale fluctuations of summer monsoon rainfall over India in relation to fluctuations in the planetary and regional scale circulation parameters. Proc Ind Acad Sci (Earth Planet Sci) 89:179–195Google Scholar
- Uma R, Lakshmi Kumar TV, Narayanan MS, Rajeevan M, Bhate J, Kumar KN (2013) Large scale features and assessment of spatial scale correspondence between TMPA and IMD rainfall datasets over Indian land mass. J Earth Syst Sci 122:573–588. https://doi.org/10.1007/s12040-013-0312-0 CrossRefGoogle Scholar