scholarly journals Mode of precipitation variability generated by coupling of ENSO with seasonal cycle in the tropical Pacific

2021 ◽  
Author(s):  
Yoshihiro Fukuda ◽  
Masahiro Watanabe ◽  
Fei‐Fei Jin
Keyword(s):  
Seasonal Cycle ◽  
Precipitation Variability ◽  
Tropical Pacific ◽  
The Tropical Pacific

scholarly journals Early and mid-Holocene climate in the tropical Pacific: seasonal cycle and interannual variability induced by insolation changes

2012 ◽  
Vol 8 (1) ◽  
pp. 505-555 ◽  
Author(s):  
Y. Luan ◽  
P. Braconnot ◽  
Y. Yu ◽  
W. Zheng ◽  
O. Marti
Keyword(s):  
Interannual Variability ◽  
Radiative Forcing ◽  
Seasonal Cycle ◽  
Tropical Pacific ◽  
Shortwave Radiation ◽  
Orbital Parameter ◽  
Sensitivity Experiment ◽  
The Mean ◽  
Mean Climate ◽  
The Tropical Pacific

Abstract. Using a coupled atmosphere-ocean model we analyze the responses of the mean climate and interannual variations in the tropical Pacific to the changes in insolation during the early and middle Holocene, for which only the variations of Earth's orbital configuration are considered. Comparison of the early and mid-Holocene with pre-industrial climate shows that both the mean climate and the characteristics of the interannual variability are altered by the changes in insolation. In particular, there is a decrease of the annual mean SST, which is characterized by a "U" shape across the tropical Pacific. The changes of the SST seasonal cycle are consistent with the changes in insolation, with the SST amplitudes weakening in the tropics. However, the larger changes in seasonality are found in the eastern Pacific, where thermodynamics and dynamical processes strengthen the SST response. The cloud radiative forcing largely reduces the shortwave radiation in the western tropical Pacific in winter causing a zonally asymmetric heat flux response. Simulations also show that ENSO strengthens across the Holocene, as suggested by coral data or lake sediments. The role of the obliquity is examined by a sensitivity experiment and we find that the obliquity change affects the seasonal displacement of ITCZ related to strength of SST meridional gradients. However, the obliquity change has little effect on SST seasonal cycle and interannual variability in eastern tropical Pacific. The precession of the orbital parameter is more important in effecting the tropical climate.

Correlative Evolutions of ENSO and the Seasonal Cycle in the Tropical Pacific Ocean

2009 ◽  
Vol 66 (4) ◽  
pp. 1041-1049 ◽  
Author(s):  
Heng Xiao ◽  
Carlos R. Mechoso
Keyword(s):  
Pacific Ocean ◽  
Seasonal Cycle ◽  
General Circulation ◽  
Tropical Pacific ◽  
Tropical Pacific Ocean ◽  
Mean Flow ◽  
Data Set ◽  
Enso Variability ◽  
Equatorial Wave ◽  
The Tropical Pacific

Abstract This study examines whether shifts between the correlative evolutions of ENSO and the seasonal cycle in the tropical Pacific Ocean can produce effects that are large enough to alter the evolution of the coupled atmosphere–ocean system. The approach is based on experiments with an ocean general circulation model (OGCM) of the Pacific basin, in which the seasonal and nonseasonal (interannually varying) components of the surface forcing are prescribed with different shifts in time. The shift would make no difference in terms of ENSO variability if the system were linear. The surface fluxes of heat and momentum used to force the ocean are taken from 1) simulations in which the OGCM coupled to an atmospheric GCM produces realistic ENSO variability and 2) NCEP reanalysis data corrected by Comprehensive Ocean–Atmosphere Data Set climatology for the 20-yr period 1980–99. It is found that the response to the shifts in terms of eastern basin heat content can be 20%–40% of the maximum interannual anomaly in the first experiment, whereas it is 10%–20% in the second experiment. In addition, the response to the shift is event dependent. A response of this magnitude can potentially generate coupled atmosphere–ocean interactions that alter subsequent event evolution. Analysis of a selected event shows that the major contribution to the response is provided by the anomalous zonal advection of seasonal mean temperature in the equatorial band. Additional OGCM experiments suggest that both directly forced and delayed signals provide comparable contributions to the response. An interpretation of the results based on the “delayed oscillator” paradigm and on equatorial wave–mean flow interaction is given. It is argued that the same oceanic ENSO anomalies in different times of the oceanic seasonal cycle can result in different ENSO evolutions because of nonlinear interactions between equatorially trapped waves at work during ENSO and the seasonally varying upper-ocean currents and thermocline structure.

scholarly journals A delay differential model of ENSO variability – Part 2: Phase locking, multiple solutions and dynamics of extrema

2010 ◽  
Vol 17 (2) ◽  
pp. 123-135 ◽  
Author(s):  
I. Zaliapin ◽  
M. Ghil
Keyword(s):  
Multiple Solutions ◽  
Seasonal Cycle ◽  
El Nino ◽  
Dimensional Space ◽  
Phase Locking ◽  
Tropical Pacific ◽  
Model Parameters ◽  
Enso Variability ◽  
Delay Differential ◽  
The Tropical Pacific

Abstract. We consider a highly idealized model for El Niño/Southern Oscillation (ENSO) variability, as introduced in an earlier paper. The model is governed by a delay differential equation for sea-surface temperature T in the Tropical Pacific, and it combines two key mechanisms that participate in ENSO dynamics: delayed negative feedback and seasonal forcing. We perform a theoretical and numerical study of the model in the three-dimensional space of its physically relevant parameters: propagation period τ of oceanic waves across the Tropical Pacific, atmosphere-ocean coupling κ, and strength of seasonal forcing b. Phase locking of model solutions to the periodic forcing is prevalent: the local maxima and minima of the solutions tend to occur at the same position within the seasonal cycle. Such phase locking is a key feature of the observed El Niño (warm) and La Niña (cold) events. The phasing of the extrema within the seasonal cycle depends sensitively on model parameters when forcing is weak. We also study co-existence of multiple solutions for fixed model parameters and describe the basins of attraction of the stable solutions in a one-dimensional space of constant initial model histories.

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