Impact of Indian Ocean warming on increasing trend in pre-monsoon rainfall and Hadley circulation over Bay of Bengal
In the present manuscript, we analyzed the pre-monsoon (March–April–May) rainfall over the Indian summer monsoon region using the Global Precipitation Climatology Project (GPCP) rainfall datasets during 1979–2015. It is found that the rainfall over the Bay of Bengal (BOB) has increased significantly and it is associated with the strengthening of local Hadley circulation over the BOB. The increasing Sea Surface Temperature (SST) over the Indian Ocean is playing an important role to the observed changes in convections and cloudiness over the BOB. In addition, the strengthening of the westerly enhances the wind speed and transports more moisture to the North Indian Ocean. In addition, warming of the SST and large-scale moisture convergence cause the rainfall to increase and the latent heat released in the process strengthens the divergent wind at 200 hPa. This strengthens the local Hadley circulation over the BOB, which may affect the monsoon strength over the Indian subcontinent, by influencing the onset of the Indian summer monsoon. This study will improve the understanding by monitoring the changes in the atmospheric processes over the BOB and the Indian subcontinent, which may result in better predictability of the Indian summer monsoon.
The authors highly acknowledge the scientific exchange and discussions with many members of the Center for Monsoon System Research group. The authors also would like to acknowledge the Institute of Atmospheric Physics, Chinese Academy of Sciences, for the materialistic support. The GPCP data were provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their website at http://www.esrl.noaa.gov/psd/. The authors also would like to thank the anonymous reviewers for their valuable suggestions. This work is supported jointly by the National Natural Science Foundation of China (Grant No. 41750110484, 41675061), the Ministry of Science and Technology of China (2016YFA0600604), and the Key Research Program of Frontier Sciences, CAS (QYZDY-SSW-DQC024).
D.C. and D.N. designed the study, and C.W. gave valuable suggestions during the research. All the authors contributed ideas in developing the research, discussed the results, and wrote the paper.
Compliance with ethical standards
The authors declare that they have no competing interest.
- Ananthakrishnan R, Srinivasan V, Ramakrishnan AR, Jambunathan R (1968) Synoptic features associated with onset of southwest monsoon over Kerala. In: Forecasting manual report no. IV-18.2. India Meteorological Department, PuneGoogle Scholar
- Danielsen EF (1993) In situ evidence of rapid, vertical, irreversible transport of lower tropospheric air into the lower tropical state-sphere by convective cloud turrets and by larger-scale upwelling in tropical stratosphere by convective cloud turrets and by larger-scale upwelling in tropical cyclones. J Geophys Res 98:8665–8681CrossRefGoogle Scholar
- IPCC (2007) The Physical Science Basis. Contribution of working group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, New York, pp 589–663Google Scholar
- Joseph PV (1990) Warm pool over the Indian Ocean and monsoon onset.. Tropical Ocean-Atmos News Lett 53:1–5Google Scholar
- Ju J, Slingo JM (1995) The Asian summer monsoon and ENSO. Q J R Meteorol Soc 106:447–462Google Scholar
- Kalnay E, Kanamitsu M, Kistler R, Collins W, Deaven E, Gandin L, Iredell M, Saha S, White G, Woolley J, Zhu Y, Chelliah M, Ebisuzaki W, Higgins W, Janowiak J, Mo K, Ropelewski C, Wang J, Leetmaa A, Reynolds R, Roy J, Joseph D (1996) The NCEP/NCAR 40-year reanalysis project. Bull Am Meteorol Soc 77:437–471CrossRefGoogle Scholar
- Ramage CS (1971) Monsoon meteorology (vol. 15 of international geophysics series). Academic, San Diego 296 ppGoogle Scholar
- Rao YP (1976) Southwest monsoon (meteorological monograph). India Meteorological Department, New Delhi 366 ppGoogle Scholar
- Roxy MK, Kapoor R, Pascal T, Raghu M, Karumuri A, Goswami BN (2015) Drying of Indian subcontinent by rapid Indian Ocean warming and a weakling land-sea thermal gradient. Nat Commun 6(7423)Google Scholar
- Shahi NK, Rai K, Pandey DK, Mishra N (2015) Seasonal prediction skill of Indian summer monsoon rainfall in ECMWF system 4 model. Clim Chang 1(4):469–475Google Scholar
- Thapliyal V, Kulshrestha SM (1991) Climate changes and trends over India. Mausam 42:333–338Google Scholar
- Wei J, Su H, Yang Z-L (2015) Impact of moisture flux convergence and soil moisture on precipitation: a case study for the southern United States with the implications for the globe. Clm Dyn 46:467–481. https://doi.org/10.1007/s00382-0152593-2