Existence of ‘mini-break’ like condition during early Indian monsoon onset years
In the context of increasing probability of advancement in onset date of Indian Summer Monsoon during recent years, precipitation and circulation features of early monsoon onset events are investigated in detail using reanalysis data and model simulations. During the onset pentad (± 2 days from the onset day), an anomalous increase in precipitation is observed over the west coast of peninsular India and Bay of Bengal during early onset years compared to normal onset years. The monsoon low level jet (LLJ) also becomes stronger during the onset pentad of early onset years particularly over the southern peninsular India. However, after a week from the onset day of early years, precipitation is considerably decreased and the LLJ become weaker. Moreover, convection over the eastern Arabian Sea and western peninsular India suppresses during that period which in turn inhibits the systematic northward propagation of monsoon rainbands. This induces a ‘mini break’ like condition immediately after a week from the onset day during early onset years. Analysis of the sea surface temperature (SST) shows that, over the north eastern Arabian Sea, a lower value of SST exists during early onset years compared to normal onset years which may have a triggering role in the formation of ‘mini break’ like condition. This aspect is examined using sensitivity simulations with the Advanced Research Weather Research and Forecasting model. Simulations with reduced SST over the north eastern Arabian Sea during normal onset years exhibits considerable reduction in precipitation over the west coast of India and weakens the LLJ over the peninsular India. Whereas simulations with enhanced SST over the north eastern Arabian Sea during early onset years show increase in the convective activities over the eastern Arabian Sea and west coast of peninsular India, and the existence of ‘mini break’ like situation disappears from those years. Thus numerical simulations confirm the relation between SST over the north eastern Arabian Sea and the formation of ‘mini break’ during early onset years.
The authors are thankful to the Editor and anonymous reviewers for their constructive comments.
- Ananthakrishnan R, Pathan JM, Aralikatti SS (1983) The onset phase of the southwest monsoon. Curr Sci 52:755–764Google Scholar
- Francis PA, Gadgil S (2009) The aberrant behaviour of the Indian monsoon in June 2009. Curr Sci 97(9):1291–1295Google Scholar
- Huffman GJ, Bolvin DT, Nelkin EJ, Wolff DB, Adler RF, Gu G, Hong Y, Bowman KP, Stocker EF (2007) The TRMM multisatellite precipitation analysis (TMPA): quasi-global, multiyear, combined-sensor precipitation estimates at fine scales. J Hydrometeor 8:38–55. https://doi.org/10.1175/JHM560.1 CrossRefGoogle Scholar
- IPCC (2014) Introduction. In climate change 2013—the physical science basis: Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, pp 119–158. https://doi.org/10.1017/CBO9781107415324.007
- Joseph PV, Simon A (2005) Weakening trend of the southwest monsoon current through peninsular India from 1950 to the present. Curr Sci 89(4):687–694Google Scholar
- Liebmann B, Smith CA (1996) Description of a complete (Interpolated) outgoing longwave radiation dataset. Bull Am Meteorol Soc 77:1275–1277Google Scholar
- Mandke S, Bhide U (2003) A study of decreasing storm frequency over Bay of Bengal. J Indian Geophys Union 7:53–58Google Scholar
- NCAR (2017) User's guide for the Advanced Research WRF (ARW) modeling system Version 3. National Center for Atmospheric Research. https://www2.mmm.ucar.edu/wrf/users/docs/user_guide_V3/contents.html. Accessed Apr 2017
- Skamarock WC, Klemp JB, Dudhia J, Gill DO, Barker DM, Duda MG, Huang X, Wang W, Powers JG (2008) A description of the advanced research WRF Version 3. NCAR Technical Note NCAR/TN–475+STRGoogle Scholar