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National Science Foundation Award #0553111

The Role of Extratropical Cooling in Determining the Level of El Nino-Southern Oscillation (ENSO) Activity

Investigator(s):

De-Zheng Sun (PI) ; Sang-Ik Shin (Co-PI) ; Amy Solomon (Co-PI)

Sponsor:

University of Colorado at Boulder, CO 80309 3034926221

Start Date/Expiration Date

2006-04-01 to 2007-03-31 (amended 2006-03-21)

Awarded Amount to Date:

$117,521

Abstract: This study addresses the question of how the level of El Nino-Southern Oscillation (ENSO) activity responds to cooling/warming over the extratropical Pacific. The possibility for a fundamental role of extratropical cooling/warming in determining the level of ENSO activity is raised by recent studies of the role of ENSO in the heat balance of the tropical Pacific. These studies suggest that ENSO acts as a heat pump--a downward and poleward heat transfer mechanism--that regulates the stability of the time-mean state of the coupled tropical ocean/atmosphere. Cooling/warming over the extratropical Pacific can modify the heat balance of the tropical Pacific and perturb the stability of the coupled tropical ocean-atmosphere system through either the "ocean tunnel" or the "atmospheric bridge"--circulations in the atmosphere and in the ocean that connect the tropical region with the extratropical region. The working hypothesis is that an extratropical cooling results in stronger ENSO activity and conversely an extratropical warming weakens ENSO variability. Such extratropical perturbations trigger a response in the level of ENSO activity as ENSO acts as a heat pump that regulates the long-term stability of the equatorial Pacific region. The PIs plan to test this hypothesis by conducting numerical experiments with varying complexity. The intellectual merit of the activity: The research will help to understand global forces controlling the level of ENSO activity, identify causes of variability of ENSO on decadal and longer time-scales, and shed light on the interaction between ENSO and the mean climate. The broader impacts resulting from the activity: Through the principal investigator's supervising graduate and postdoctoral students and participating with teaching in the University of Colorado, the research is expected to contribute significantly to the education and training of interested citizens as well as future scientists. Whether ENSO will become more energetic in response to global warming is an issue of high societal concern. The research will help to address this issue by delineating the fundamental forces controlling the level of ENSO activity.

NSF Org:

ATM - Division of Atmospheric Sciences

Award Number:

0553111

Award Instrument:

Continuing grant

Program Manager:

Jay S. Fein
ATM Division of Atmospheric Sciences
GEO Directorate for Geosciences

NSF Program(s):

CLIMATE & LARGE-SCALE DYNAMICS, PHYSICAL OCEANOGRAPHY

Field Application(s):

Climate Related Activities

Program Reference Code(s):

CLIMATE MODELING & PREDICTION, 1303
CLIMATE VARIABILITY AND PREDICTABILITY, 1324
INTERDISCIPLINARY PROPOSALS, 4444

Program Element Code(s):

5740
PHYSICAL OCEANOGRAPHY, 1610