Spatial variation of different rain systems during El Niño and La Niña periods over India and adjoining ocean
The spatial patterns of rainfall and rain systems during El Niño and La Niña episodes are distinctly different due to the longitudinal variations in the Walker circulation ascent/decent branches over India and adjoining Oceans. In order to examine these differences, 16 years (1998–2013) of Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) data have been utilized. TRMM-PR delineated precipitating systems (convective, stratiform and shallow) show distinctly different spatial structures over India and adjoining Oceans during El Niño and La Niña episodes. During the El Niño episode, the occurrence of deep systems is high over north of 20°N latitude, and shallow systems are plentiful over south of 20°N latitude. On the other hand, during the La Niña episodes, the occurrence of shallow systems is in excess over Pakistan, central India, northwest Arabian Sea, southwest Indian Ocean and northern Bay of Bengal while the deep systems are abundant over west coast of India, Ganges basin, eastern Indian Ocean and Arabian Sea. The excess convective rain pixels observed during El Niño years are from deep and deep and wide convective core systems due to increase in the CAPE, nevertheless the broad stratiform rain systems are prevalent during La Niña years due to the high convergence of moisture flux and mid-tropospheric upward motion. Though the convective occurrence is more, their intensity is weaker during El Niño years than during La Niña years, indicating the intense nature of convective storms during La Niña episodes.
KeywordsEl Niño La Niña Spatial structure of rainfall Southwest monsoon
The authors express their profound gratitude to the TRMM, University of Washington, ECMWF and NOAA/OAR/ESRL PSD, Boulder, Colorado, USA teams for providing the necessary rainfall, 3D gridded TRMM-PR data, ERA-Interim data and GPCP Precipitation data, respectively. Special thank goes to Prof. J. Srinivasan for his fruitful discussions. We profoundly thank the two anonymous reviewers for their valuable suggestions in improving the quality of the manuscript.
- Adler RF, Huffman GJ, Chang A, Ferraro R, Xie P-P, Janowiak J, Rudolf B, Schneider U, Curtis S, Bolvin D, Gruber A, Susskind J, Arkin P, Nelkin E (2003) The version-2 global precipitation climatology project (GPCP) monthly precipitation analysis (1979–present). J Hydrometeor 4(6):1147–1167CrossRefGoogle Scholar
- Emanuel KA (1994) Atmospheric convection. Oxford University Press, OxfordGoogle Scholar
- Gadgil S, Vinayachandran PN, Francis PA (2003) Droughts of the Indian summer monsoon: role of clouds over the Indian Ocean. Curr Sci 85:1713–1719Google Scholar
- IPCC (Intergovernmental Panel on Climate Change) Climate Change (2007) The physical science basis: contribution of working group I to the fourth assessment report of the Intergovernmental Panel on Climate Change, edited by S. Solomon et al.. Cambridge University Press, Cambridge, p 1009Google Scholar
- Oza M, Kishtawal CM (2014) Spatial analysis of Indian summer monsoon rainfall. J Geomat 8:40–47Google Scholar
- Saha KR (1970) Zonal anomaly of sea surface temperature in equatorial Indian Ocean and its possible effect upon monsoon circulation. Tellus 4:403–409Google Scholar
- Shukla J (1987) Interannual variability of monsoon. In: Fein JS, Stephens PL (eds) Monsoons. Wiley, New York, pp 399–464Google 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
- Vinayachandran PN, Francis PA, Rao SA (2009) Indian Ocean dipole: processes and impacts. In: Current trends in science, platinum jubilee special volume of the Indian Academy of Sciences, Indian Academy of Science, Bangalore, India, pp 569–589Google Scholar