Climate Dynamics

, Volume 44, Issue 1–2, pp 191–202 | Cite as

The influence of ENSO on the equatorial Atlantic precipitation through the Walker circulation in a CGCM

  • Wataru Sasaki
  • Takeshi Doi
  • Kelvin J. Richards
  • Yukio Masumoto
Article

Abstract

The link between El Niño/Southern Oscillation (ENSO) and the equatorial Atlantic precipitation during boreal spring (March–April–May) is explored using a coupled general circulation model (CGCM). Interannual variability of the equatorial Atlantic sea surface temperature (SST) in the CGCM is excluded by nudging the modeled SST toward the climatological monthly mean of observed SST in the equatorial Atlantic, but full air–sea coupling is allowed elsewhere. It is found that the equatorial Atlantic precipitation is reduced (increased) during El Niño (La Niña) in the case where the interannual variability of the equatorial Atlantic SST is disabled. The precipitation anomalies in the equatorial Atlantic during ENSO are not strongly associated with the meridional migration of the Atlantic inter-tropical convergence zone. We find the reduced precipitation in the equatorial Atlantic during El Niño is associated with an enhanced Atlantic Walker circulation characterized by strengthened low-level easterlies and anomalous dry, downward winds over the equatorial Atlantic, while the Pacific Walker circulation is weakened. The upper-level anomalous westerlies over the equatorial Atlantic are consistent with a Matsuno–Gill-type response to heating in the eastern equatorial Pacific. Our results of the CGCM experiments suggest that changes to the Walker circulation induced by ENSO contribute significantly to changes in precipitation over the equatorial Atlantic.

Keywords

ITCZ ENSO Equatorial Atlantic Coupled general circulation model 

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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Wataru Sasaki
    • 1
  • Takeshi Doi
    • 2
  • Kelvin J. Richards
    • 3
  • Yukio Masumoto
    • 2
    • 4
  1. 1.Center for Earth Information Science and TechnologyJapan Agency for Marine Earth Science and TechnologyYokohamaJapan
  2. 2.Application LaboratoryJapan Agency for Marine Earth Science and TechnologyYokohamaJapan
  3. 3.International Pacific Research Center/SOESTUniversity of Hawaii at ManoaHonoluluUSA
  4. 4.Department of Earth and Planetary ScienceThe University of TokyoTokyoJapan

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