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Geophysical Monograph Series

 

Keywords

  • Ocean-atmosphere interaction
  • Climatic changes

Article

GEOPHYSICAL MONOGRAPH SERIES, VOL. 147, PP. 71-83, 2004

The control of meridional differential surface heating over the level of ENSO activity: A heat-pump hypothesis

De-Zheng Sun

NOAA-CIRES/Climate Diagnostics Center, Boulder, Colorado


Numerical experiments with a coupled model have been carried out to test the heat-pump hypothesis for ENSO. The hypothesis states that the level of ENSO activity is controlled by the meridional differential surface heating over the Pacific: either an enhanced surface heating over the equatorial region or an enhanced cooling over the subtropical/extratropical ocean may result in a regime with stronger ENSO events. Moreover, ENSO may b e a mechanism that regulates the long-term stability of the coupled equatorial ocean-atmosphere system. The results from the numerical experiments are shown to b e consistent with this hypothesis. A stronger tropical heating or a stronger subtropical/extratropical cooling tends to increase the contrast between the SST in the tropical western Pacific warm-pool and the temperature of the equatorial thermocline water and thereby destabilize the coupled equatorial ocean-atmosphere system. In response, a regime with stronger ENSO events sets in. The stronger ENSO events transport more heat downward and poleward, cooling the warmpool SST and warming the equatorial thermocline water. In the presence of ENSO, the difference between the time-mean warm-pool SST and the time-mean temperature of the equatorial thermocline water is found to be insensitive to changes in the external forcing.

Citation: Sun, D.-Z. (2004), The control of meridional differential surface heating over the level of ENSO activity: A heat-pump hypothesis, in Earth's Climate: The Ocean-Atmosphere Interaction, Geophys. Monogr. Ser., vol. 147, edited by C. Wang, S.-P. Xie, and J. A. Carton, pp. 71–83, AGU, Washington, D. C., doi:10.1029/147GM04.

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