Changes in equatorial zonal circulations and precipitation in the context of the global warming and natural modes
The strengthening and westward shift of Pacific Walker Circulation (PWC) is observed during the recent decades. However, the relative roles of global warming and natural variability on the change in PWC unclearly remain. By conducting numerical atmospheric general circulation model (AGCM) experiments using the spatial SST patterns in the global warming and natural modes which are obtained by the multi-variate EOF analysis from three variables including precipitation, sea surface temperature (SST), and divergent zonal wind, we indicated that the westward shift and strengthening of PWC are caused by the global warming SST pattern in the global warming mode and the negative Interdecadal Pacific Oscillation-like SST pattern in the natural mode. The SST distribution of the Pacific Ocean (PO) has more influence on the changes in equatorial zonal circulations and tropical precipitation than that of the Indian Ocean (IO) and Atlantic Ocean (AO). The change in precipitation is also related to the equatorial zonal circulations variation through the upward and downward motions of the circulations. The IO and AO SST anomalies in the global warming mode can affect on the changes in equatorial zonal circulations, but the influence of PO SST disturbs the changes in Indian Walker Circulation and Atlantic Walker Circulation which are affected by the anomalous SST over the IO and AO. The zonal shift of PWC is found to be highly associated with a zonal gradient of SST over the PO through the idealized numerical AGCM experiments and predictions of CMIP5 models.
KeywordsEquatorial zonal circulations Global warming Interdecadal Pacific Oscillation Pacific Walker Circulation
This work was supported by the National Research Foundation of Korea (NRF) through a Global Research Laboratory (GRL) grant (MEST 2011-0021927).
- Kousky VE, Kagano MT, Cavalcanti IF (1984) A review of the Southern Oscillation: oceanic-atmosphric circulation changes and related rainfall anomalies. Tellus A 36:490–504Google Scholar
- Luo JJ, Sasaki W, Masumoto Y (2012) Indian Ocean warming modulates Pacific climate change. Proc Natl Acad Sci 109:18701–18706Google Scholar
- McGregor S, Timmermann A, Stuecker MF et al (2014) Recent Walker circulation strengthening and Pacific cooling amplified by Atlantic warming. Nat Clim Change 4:888–892Google Scholar
- Moon HJ, Kim BH, Oh HE, Lee JY, Ha KJ (2014) Future change using the CMIP5 MME and best models: I. near and long term future change of temperature and precipitation over East Asia. Atmos Korean Meteorol Soc 24(3):403–417 (Korean)Google Scholar
- Parker DE, Rayner NA, Horton EB, Folland CK (1999) Development of the Hadley Center sea ice and sea surface temperature data sets (HadISST). WMO workshop on advances in marine climatology-CLIMAR99. Environment Canada, Vancouver, BC, pp 194–203Google Scholar
- Philander S (1990) El Niño, La Niña, and the southern oscillation. Academic, San DiegoGoogle Scholar
- Roeckner E et al (1996) The atmospheric general circulation model ECHAM-4: Model description and simulation of present-day climate. Rep. 218, 99 pp. Max Planck Inst. For Meteorol, Hamburg, GermanyGoogle Scholar
- Tokinaga H, Xie S, Deser C, Kosaka Y, Okumura YM (2012a) Slowdown of the Walker circulation driven by tropical Indo-Pacific warming. Nat Res Lett 491:439–443Google Scholar
- Yu B, Zwiers FW (2010) Changes in equatorial atmospheric zonal circulations in recent decades. Geophys Res Lett 37:L05701Google Scholar
- Zhang L (2016) The roles of external forcing and natural variability in global warming hiatuses. Clim Dyn 47:3157–3169. doi: 10.1007/s00382-016-3018-6