North Equatorial Indian Ocean Convection and Indian Summer Monsoon June Progression: a Case Study of 2013 and 2014
- 183 Downloads
The consecutive summer monsoons of 2013 and 2014 over the Indian subcontinent saw very contrasting onsets and progressions during the initial month. While the 2013 monsoon saw the timely onset and one of the fastest progressions during the recent decades, 2014 had a delayed onset and a slower progression phase. The monthly rainfall of June 2013 was +34 %, whereas in 2014 it was −43 % of its long-period average. The progress/onset of monsoon in June is influenced by large-scale circulation and local feedback processes. But, in 2013 (2014), one of the main reasons for the timely onset and fastest progression (delayed onset and slower progression) was the persistent strong (weak) convection over the north equatorial Indian Ocean during May. This resulted in a strong (weak) Hadley circulation with strong (weak) ascent and descent over the north equatorial Indian Ocean and the South Indian Ocean, respectively. The strong (weak) descent over the south Indian Ocean intensified (weakened) the Mascarene High, which in turn strengthened (weakened) the cross-equatorial flow and hence the monsoonal circulation.
KeywordsISM Mascarene High Hadley circulation OLR Cross-equatorial flow ENSO
The authors wish to thank the editor and the two anonymous reviewers for their insightful comments that helped improve the manuscript. The data have been taken from websites and all data sources have been duly acknowledged. Computational and graphical analyses required for the study were completed with the freely available softwares, e.g., Ferret, NCL and xmgrace.
- IMD. (2013). Monsoon 2013: A report. IMD Met Monograph No.: ESSO/IMD/SYNOPTIC MET/01-2014/15. India Met Department Eds Pai DS and Bhan SC. http://www.imdpune.gov.in/.
- Liebmann, B., & Smith, C. A. (1996). Description of a complete (interpolated) outgoing longwave radiation dataset. Bulletin of the American Meteorological Society, 77, 1275–1277.Google Scholar
- Shukla, J. (1987). Interannual variability of monsoon. In J. S. Fein & P. L. Stephens (Eds.), Monsoons (pp. 399–464). New York: Wiley.Google Scholar
- Sikka, D. R. (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. Proceedings of the Indian Academy of Sciences (Earth and Planetary Sciences), 89, 179–195.Google Scholar