scholarly journals An off-line, numerically efficient initialization scheme in an oceanic general circulation model for El Niño–Southern Oscillation prediction

2004 ◽  
Vol 109 (C5) ◽  
Author(s):  
Youmin Tang
Keyword(s):  
General Circulation Model ◽  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Circulation Model ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Oceanic General Circulation Model ◽  
Initialization Scheme

scholarly journals Extratropical Influences on the El Niño–Southern Oscillation through the Late Quaternary

2007 ◽  
Vol 20 (5) ◽  
pp. 788-800 ◽  
Author(s):  
Andrew B. G. Bush
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Late Quaternary ◽  
Circulation Model ◽  
Linear Stability Theory ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Enso Events

Abstract A sequence of numerical simulations with a coupled atmosphere–ocean general circulation model configured for particular times during the late Quaternary shows that simulated El Niño–Southern Oscillation (ENSO) events decrease in frequency from the Last Glacial Maximum (LGM) to today, in accord with linear stability theory, but increase in amplitude. Diagnostic analyses indicate that altered momentum fluxes from midlatitude eddy activity caused by changes in orbital forcing (in the Holocene) and topographic forcing (at the LGM) regulate the strength of climatological easterlies and therefore affect both the tropical mean state and the characteristics of interannual variability. The fact that climatic teleconnections associated with paleo-ENSO are fundamentally different during these times suggests a way in which to reconcile some of the existing discrepancies amongst interpretations of proxy records and numerical paleoclimate simulations.

scholarly journals El Niño–Southern Oscillation Simulation at 6000 Years before Present with the MRI-CGCM2.3: Effect of Flux Adjustment

2007 ◽  
Vol 20 (11) ◽  
pp. 2484-2499 ◽  
Author(s):  
Akio Kitoh ◽  
Tatsuo Motoi ◽  
Shigenori Murakami
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Circulation Model ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Before Present ◽  
Equatorial Pacific Ocean ◽  
Flux Adjustment

Abstract Modulation of El Niño–Southern Oscillation at the mid-Holocene [6000 yr before present (6 ka)] is investigated with a coupled ocean–atmosphere general circulation model. The model is integrated for 300 yr with 6-ka and present (0 ka) insolation both with and without flux adjustment, and the effect of flux adjustment on the simulation of El Niño is investigated. The response in the equatorial Pacific Ocean in 6 ka is in favor of weaker El Niño variability resulting from lowered sea surface temperature (SST) and a more diffuse thermocline. Atmospheric sensitivity in 6 ka is larger than that in 0 ka because of increased trade winds, while oceanic sensitivity in 6 ka is weaker than that in 0 ka, resulting from destabilization of the upper ocean, both in the flux- and non-flux-adjusted experiments. However, the use of flux adjustment causes a difference in the total response. El Niño variability in 6 ka does not change much from that in 0 ka with the flux-adjusted case, while the 6-ka El Niño variability is weaker without flux adjustment. Because the observed proxy data suggest weaker El Niño variability in the mid-Holocene, the non-flux-adjusted version gives a more reasonable response despite a larger bias in its basic states, implying that nondistortion of sensitivity to forcing is more important.

scholarly journals Inferred changes in El Niño–Southern Oscillation variance over the past six centuries

2013 ◽  
Vol 9 (5) ◽  
pp. 2269-2284 ◽  
Author(s):  
S. McGregor ◽  
A. Timmermann ◽  
M. H. England ◽  
O. Elison Timm ◽  
A. T. Wittenberg
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Good Representation ◽  
Modeling Framework ◽  
Proxy Data ◽  
Proxy Reconstructions

Abstract. It is vital to understand how the El Niño–Southern Oscillation (ENSO) has responded to past changes in natural and anthropogenic forcings, in order to better understand and predict its response to future greenhouse warming. To date, however, the instrumental record is too brief to fully characterize natural ENSO variability, while large discrepancies exist amongst paleo-proxy reconstructions of ENSO. These paleo-proxy reconstructions have typically attempted to reconstruct ENSO's temporal evolution, rather than the variance of these temporal changes. Here a new approach is developed that synthesizes the variance changes from various proxy data sets to provide a unified and updated estimate of past ENSO variance. The method is tested using surrogate data from two coupled general circulation model (CGCM) simulations. It is shown that in the presence of dating uncertainties, synthesizing variance information provides a more robust estimate of ENSO variance than synthesizing the raw data and then identifying its running variance. We also examine whether good temporal correspondence between proxy data and instrumental ENSO records implies a good representation of ENSO variance. In the climate modeling framework we show that a significant improvement in reconstructing ENSO variance changes is found when combining information from diverse ENSO-teleconnected source regions, rather than by relying on a single well-correlated location. This suggests that ENSO variance estimates derived from a single site should be viewed with caution. Finally, synthesizing existing ENSO reconstructions to arrive at a better estimate of past ENSO variance changes, we find robust evidence that the ENSO variance for any 30 yr period during the interval 1590–1880 was considerably lower than that observed during 1979–2009.

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