scholarly journals Diversity of the Madden–Julian Oscillation: Initiation Region Modulated by the Interaction between the Intraseasonal and Interannual Variabilities

2021 ◽  
Vol 34 (6) ◽  
pp. 2297-2318
Author(s):  
Daisuke Takasuka ◽  
Masaki Satoh
Keyword(s):  
El Niño ◽  
El Nino ◽  
Eastern Pacific ◽  
Boreal Winter ◽  
Madden Julian Oscillation ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Sst Variability ◽  
Circulation Patterns ◽  
The Difference

AbstractAs one of the aspects of the diversity of the Madden–Julian oscillation (MJO), the modulation of initiation regions of the boreal-winter MJO is studied in terms of the relationship between intraseasonal and interannual variabilities. MJOs are categorized as those initiating in the Indian Ocean (IO), Maritime Continent (MC), and western Pacific (WP), referred to herein as IO-MJOs, MC-MJOs, and WP-MJOs, respectively. The composite analyses for each MJO category using observational data reveal that the diversity of MJO initiation regions directly results from the modulation of areas where horizontal advective premoistening efficiently occurs via intraseasonal/synoptic-scale winds. This is supported by the difference in the zonal location of equatorial intraseasonal circulations established before MJO initiation, which is related to a spatial change in background convection and associated Walker circulations forced by interannual sea surface temperature (SST) variability. Compared to IO-MJOs (favored in the climatological background on average), MC-MJOs tend to be realized under the eastern-Pacific El Niño–like condition, as a result of eastward-shifted intraseasonal convection and circulation patterns induced by background suppressed convection in the eastern MC. WP-MJOs are frequently initiated under the central-Pacific El Niño–like and positive IO dipole–like conditions, in which the WP is selectively moistened with the aid of background enhanced (suppressed) convection over the WP (the southeastern IO and the central-to-eastern Pacific). This major tendency derived from sample-limited observations is verified by a set of 15-yr numerical experiments with a global nonhydrostatic MJO-permitting model under a perpetual boreal-winter condition where observation-based SSTs are prescribed.

scholarly journals Seasonal Synchronization of a Simple Stochastic Dynamical Model Capturing El Niño Diversity

2017 ◽  
Vol 30 (24) ◽  
pp. 10047-10066 ◽  
Author(s):  
Sulian Thual ◽  
Andrew Majda ◽  
Nan Chen
Keyword(s):  
El Niño ◽  
Cloud Cover ◽  
El Nino ◽  
Southern Oscillation ◽  
Eastern Pacific ◽  
Dynamical Model ◽  
Boreal Winter ◽  
Convective Activity ◽  
Central Pacific ◽  
Central Pacific El Niño

Recently, a simple stochastic dynamical model was developed that automatically captures the diversity and intermittency of El Niño–Southern Oscillation (ENSO) in nature, where state-dependent stochastic wind bursts and nonlinear advection of sea surface temperature (SST) are coupled to simple ocean–atmosphere processes that are otherwise deterministic, linear, and stable. In the present article, it is further shown that the model can reproduce qualitatively the ENSO synchronization (or phase locking) to the seasonal cycle in nature. This goal is achieved by incorporating a cloud radiative feedback that is derived naturally from the model’s atmosphere dynamics with no ad hoc assumptions and accounts in simple fashion for the marked seasonal variations of convective activity and cloud cover in the eastern Pacific. In particular, the weak convective response to SSTs in boreal fall favors the eastern Pacific warming that triggers El Niño events while the increased convective activity and cloud cover during the following spring contributes to the shutdown of those events by blocking incoming shortwave solar radiations. In addition to simulating the ENSO diversity with realistic non-Gaussian statistics in different Niño regions, the eastern Pacific moderate and super El Niño and the central Pacific El Niño and La Niña show a realistic chronology with a tendency to peak in boreal winter as well as decreased predictability in spring consistent with the persistence barrier in nature. The incorporation of other possible seasonal feedbacks in the model is also documented for completeness.

scholarly journals Ocean Processes Affecting the Twenty-First-Century Shift in ENSO SST Variability

2016 ◽  
Vol 29 (19) ◽  
pp. 6861-6879 ◽  
Author(s):  
Cong Guan ◽  
Michael J. McPhaden
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
First Century ◽  
Eastern Pacific ◽  
Enso Cycle ◽  
Central Pacific ◽  
Temperature Variance ◽  
Sst Variability ◽  
Twenty First Century

Abstract Sea surface temperature (SST) variability associated with El Niño–Southern Oscillation (ENSO) slightly increased in the central Pacific Ocean but weakened significantly in the eastern Pacific at the beginning of twenty-first century relative to 1980–99. This decadal shift led to the greater prominence central Pacific (CP) El Niño events during the 2000s relative to the previous two decades, which were dominated by eastern Pacific (EP) events. To expand upon previous studies that have examined this shift in ENSO variability, temperature and temperature variance budgets are examined in the mixed layer of the Niño-3 (5°S–5°N, 150°–90°W) and Niño-4 (5°S–5°N, 160°E–150°W) regions from seven ocean model products spanning the period 1980–2010. This multimodel-product-based approach provides a robust assessment of dominant mechanisms that account for decadal changes in two key index regions. A temperature variance budget perspective on the role of thermocline feedbacks in the ENSO cycle based on recharge oscillator theory is also presented. As found in previous studies, thermocline and zonal advective feedbacks are the most important positive feedbacks for generating ENSO SST variance, and thermodynamic damping is the largest negative feedback for damping ENSO variance. Consistent with the shift toward more CP El Niños after 2000, thermocline feedbacks experienced a substantial reduction from 1980 to 1999 and into the 2000s, while zonal advective feedbacks were less affected. Negative feedbacks likewise weakened after 2000, particularly thermal damping in the Niño-3 region and the nonlinear sink of variance in both regions.

scholarly journals Impact of ENSO regimes on developing- and decaying-phase precipitation during rainy season in China

2017 ◽  
Vol 21 (11) ◽  
pp. 5415-5426 ◽  
Author(s):  
Qing Cao ◽  
Zhenchun Hao ◽  
Feifei Yuan ◽  
Zhenkuan Su ◽  
Ronny Berndtsson ◽  
...  
Keyword(s):  
El Niño ◽  
Rainy Season ◽  
El Nino ◽  
Southern Oscillation ◽  
Precipitation Anomaly ◽  
Eastern Pacific ◽  
Central Pacific ◽  
Enso Modoki ◽  
Average Precipitation ◽  
The Difference

Abstract. This study investigated the influence of five El Niño–Southern Oscillation (ENSO) types on rainy-season precipitation in China: central Pacific warming (CPW), eastern Pacific cooling (EPC), eastern Pacific warming (EPW), conventional ENSO and ENSO Modoki. The multi-scale moving t test was applied to determine the onset and withdrawal of rainy season. Results showed that the precipitation anomaly can reach up to 30 % above average precipitation during decaying CPW and EPW phases. Developing EPW could cause decreasing precipitation over large areas in China with 10–30 % lower than average precipitation in most areas. Conventional El Niño in the developing phase had the largest influence on ENSO-related precipitation among developing ENSO and ENSO Modoki regimes. Decaying ENSO also showed a larger effect on precipitation anomalies, compared to decaying ENSO Modoki. The difference between rainy-season precipitation under various ENSO regimes may be attributed to the combined influence of anti-cyclone in the western North Pacific and the Indian monsoon. Stronger monsoon and anti-cyclone are associated with enhanced rainy-season precipitation. The results suggest a certain predictability of rainy-season precipitation related to ENSO regimes.

scholarly journals Impact of ENSO regimes on developing and decaying phase precipitation during rainy season in China

2017 ◽  
Author(s):  
Qing Cao ◽  
Zhenchun Hao ◽  
Feifei Yuan ◽  
Zhenkuan Su ◽  
Ronny Berndtsson ◽  
...  
Keyword(s):  
El Niño ◽  
Rainy Season ◽  
El Nino ◽  
Southern Oscillation ◽  
Precipitation Anomaly ◽  
Eastern Pacific ◽  
Central Pacific ◽  
Enso Modoki ◽  
Average Precipitation ◽  
The Difference

Abstract. This study investigated the influence of five El Niño‐Southern Oscillation (ENSO) types (i.e., Central Pacific Warming (CPW), Eastern Pacific Cooling (EPC), Eastern Pacific Warming (EPW), conventional ENSO, and ENSO Modoki) on rainy-season precipitation in China. The multi-scale moving t-test was applied to determine the onset and withdrawal of rainy season. Results showed that there is a higher probability for flooding during decaying CPW and EPW phases in most parts of China with a largest precipitation anomaly reaching 30 % above average precipitation. Developing EPW could trigger droughts over large areas in China with 10–30 % lower than average precipitation in most areas. Conventional El Niño in the developing phase had the largest influence on ENSO-related precipitation among developing ENSO and ENSO Modoki regimes. Decaying ENSO also showed larger effect on the occurrence of drought and flood, compared to decaying ENSO Modoki. The difference between rainy-season precipitation under various ENSO regimes may be attributed to the combined influence of anti-cyclone in the western North Pacific and the Indian monsoon. Stronger monsoon and anti-cyclone are associated with enhanced rainy-season precipitation. The results suggest a certain predictability of rainy-season precipitation related to ENSO regimes.

scholarly journals Two-year consecutive concurrences of positive Indian Ocean Dipole and Central Pacific El Niño preconditioned the 2019/2020 Australian “black summer” bushfires

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Guojian Wang ◽  
Wenju Cai
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
El Nino ◽  
Greenhouse Warming ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Positive Indian Ocean Dipole ◽  
The Future ◽  
Rainfall Anomalies

Abstract The 2019/20 Australian black summer bushfires were particularly severe in many respects, including its early commencement, large spatial coverage, and large number of burning days, preceded by record dry and hot anomalies. Determining whether greenhouse warming has played a role is an important issue. Here, we examine known modes of tropical climate variability that contribute to droughts in Australia to provide a gauge. We find that a two-year consecutive concurrence of the 2018 and 2019 positive Indian Ocean Dipole and the 2018 and 2019 Central Pacific El Niño, with the former affecting Southeast Australia, and the latter influencing eastern and northeastern Australia, may explain many characteristics of the fires. Such consecutive events occurred only once in the observations since 1911. Using two generations of state-of-the-art climate models under historical and a business-as-usual emission scenario, we show that the frequency of such consecutive concurrences increases slightly, but rainfall anomalies during such events are stronger in the future climate, and there are drying trends across Australia. The impact of the stronger rainfall anomalies during such events under drying trends is likely to be exacerbated by greenhouse warming-induced rise in temperatures, making such events in the future even more extreme.

Sign in / Sign up

Export Citation Format

Share Document