The Response of a Stochastically Forced ENSO Model to Observed Off-Equatorial Wind Stress Forcing

McGregor, Shayne and Holbrook, Neil J. and Power, Scott B. (2009) The Response of a Stochastically Forced ENSO Model to Observed Off-Equatorial Wind Stress Forcing. Journal of Climate, 22 (10). pp. 2512-2525. ISSN 0894-8755


This study investigates the response of a stochastically forced coupled atmosphere-ocean model of the equatorial Pacific to off-equatorial wind stress anomaly forcing. The intermediate-complexity coupled ENSO model comprises a linear, first baroclinic mode, ocean shallow water model with a steady-state, two-pressure level (250 and 750 mb) atmospheric component that has been linearized about a state of rest on the β plane. Estimates of observed equatorial region stochastic forcing are calculated from NCEP-NCAR reanalysis surface winds for the period 1950-2006 using singular value decomposition. The stochastic forcing is applied to the model both with and without off-equatorial region wind stress anomalies (i.e., poleward of 12.5° latitude). It is found that the multiyear changes in the equatorial Pacific thermocline depth 'background state' induced by off-equatorial forcing can affect the amplitude of modeled sea surface temperature anomalies by up to 1°C. Moreover, off-equatorial wind stress anomalies increased the modeled amplitude of the two biggest El Niño events in the twentieth century (1982/83 and 1997/98) by more than 0.5°C, resulting in a more realistic modeled response. These equatorial changes driven by off-equatorial region wind stress anomalies are highly predictable to two years in advance and may be useful as a physical basis to enhance multiyear probabilistic predictions of ENSO indices. © 2009 American Meteorological Society.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 05 Jan 2022 23:12
Last Modified: 05 Jan 2022 23:12
Uncontrolled Keywords: Probability Theory; Applied Mathematics; Inorganic Compounds; Organic Compounds; Ocean Engineering; Oceanography, General; Atmospheric Properties; Strength of Building Materials; Mechanical Properties; Buildings and Towers; Air-sea interaction; Air-sea interaction; THE ATMOSPHERE; Atmospheric components; Baroclinic mode; ENSO models; Equatorial forcing; Equatorial Pacific; Equatorial regions; Equatorial winds; Multiyear changes; Ocean model; Pressure level; Probabilistic prediction; Reanalysis; Sea surface temperature anomalies; Shallow water model; Stochastic forcing; Surface winds; Thermocline depth; Twentieth century;
Fields of Research (2008): 04 Earth Sciences > 0401 Atmospheric Sciences > 040105 Climatology (excl.Climate Change Processes)
Fields of Research (2020): 37 EARTH SCIENCES > 3702 Climate change science > 370202 Climatology
Socio-Economic Objectives (2008): D Environment > 96 Environment > 9603 Climate and Climate Change > 960304 Climate Variability (excl. Social Impacts)
Socio-Economic Objectives (2020): 19 ENVIRONMENTAL POLICY, CLIMATE CHANGE AND NATURAL HAZARDS > 1905 Understanding climate change > 190502 Climate variability (excl. social impacts)
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