Indo-Pacific warm pool expansion modulates MJO lifecycle

2020 ◽  
Author(s):  
Panini Dasgupta ◽  
Roxy Mathew Koll ◽  
Michael J. McPhaden ◽  
Tamaki Suematsu ◽  
Chidong Zhang ◽  
...  
Keyword(s):  
Life Cycle ◽  
Indian Ocean ◽  
Southern Oscillation ◽  
Average Rate ◽  
Warm Pool ◽  
Dominant Mode ◽  
Maritime Continent ◽  
Pacific Warm Pool ◽  
The Indian Ocean ◽  
The Impact

<p>The Madden–Julian Oscillation (MJO) is the most dominant mode of intraseasonal<br>variability in the tropics, characterized by an eastward propagating zonal circulation pattern<br>and rain bands. MJO is very crucial phenomenon due to its interactions with other<br>timescales of ocean-atmosphere like El Niño Southern Oscillation, tropical cyclones,<br>monsoons, and the extreme rainfall events all across the globe. MJO events travel almost<br>half of the globe along the tropical oceans, majorly over the Indo-Pacific Warm Pool<br>(IPWP) region. This IPWP region has been warming during the twentieth and early twenty-<br>first centuries in response to increased anthropogenic emissions of greenhouse gases and<br>is projected to warm further. However, the impact of the warming of the IPWP region on<br>the MJO life cycle is largely unknown. Here we show that rapid warming over the IPWP<br>region during 1981–2018 has significantly changed the MJO life cycle, with its residence<br>time decreasing over the Indian Ocean by 3–4 days, and increasing over the Indo-Pacific<br>Maritime Continent by 5–6 days. We find that these changes in the MJO life cycle are<br>associated with a twofold expansion of the Indo-Pacific warm pool. The warm pool has<br>been expanding on average by 2.3 × 105 km2 per year during 1900–2018 and at an<br>accelerated average rate of 4 × 105 km2 per year during 1981–2018. The accelerated<br>warm pool expansion has increased moisture in the lower and middle troposphere over<br>IPWP and thereby increased the gradient of lower-middle tropospheric moisture between<br>the Indian Ocean and western Pacific. This zonal gradient of moisture between the Indian Ocean<br>and west Pacific and the increased subsidence over the Indian ocean due to increased<br>convective duration of MJO over maritime continent are likely the reasons behind the<br>changing lifecycle of MJO.</p>

Recent Atmospheric Variability at Kibo Summit, Kilimanjaro, and Its Relation to Climate Mode Activity

2018 ◽  
Vol 31 (10) ◽  
pp. 3875-3891 ◽  
Author(s):  
Emily Collier ◽  
Thomas Mölg ◽  
Tobias Sauter
Keyword(s):  
Indian Ocean ◽  
Current Knowledge ◽  
Southern Oscillation ◽  
Strong Association ◽  
Atmospheric Modeling ◽  
High Mountain ◽  
Atmospheric Variability ◽  
Rain Season ◽  
The Indian Ocean ◽  
The Impact

Abstract Accurate knowledge of the impact of internal atmospheric variability is required for the detection and attribution of climate change and for interpreting glacier records. However, current knowledge of such impacts in high-mountain regions is largely based on statistical methods, as the observational data required for process-based assessments are often spatially or temporally deficient. Using a case study of Kilimanjaro, 12 years of convection-permitting atmospheric modeling are combined with an 8-yr observational record to evaluate the impact of climate oscillations on recent high-altitude atmospheric variability during the short rains (the secondary rain season in the region). The focus is on two modes that have a well-established relationship with precipitation during this season, El Niño–Southern Oscillation and the Indian Ocean zonal mode, and demonstrate their strong association with local and mesoscale conditions at Kilimanjaro. Both oscillations correlate positively with humidity fluctuations, but the association is strongest with the Indian Ocean zonal mode in the air layers near and above the glaciers because of changes in zonal circulation and moisture transport, emphasizing the importance of the moisture signal from this basin. However, the most anomalous conditions are found during co-occurring positive events because of the combined effects of the (i) extended positive sea surface temperature anomalies, (ii) enhanced atmospheric moisture capacity from higher tropospheric temperatures, (iii) most pronounced weakening of the subsiding branch of the Indian Ocean Walker circulation over East Africa, and (iv) stronger monsoonal moisture fluxes upstream from Kilimanjaro. This study lays the foundation for unraveling the contribution of climate modes to observed changes in Kilimanjaro’s glaciers.

Impact of Indo-Pacific Feedback Interactions on ENSO Dynamics Diagnosed Using Ensemble Climate Simulations

2012 ◽  
Vol 25 (21) ◽  
pp. 7743-7763 ◽  
Author(s):  
A. Santoso ◽  
M. H. England ◽  
W. Cai
Keyword(s):  
Indian Ocean ◽  
Climate Model ◽  
Southern Oscillation ◽  
Ocean Basin ◽  
Climate Feedback ◽  
Enso Events ◽  
Thermocline Feedback ◽  
Enso Dynamics ◽  
The Indian Ocean ◽  
The Impact

The impact of Indo-Pacific climate feedback on the dynamics of El Niño–Southern Oscillation (ENSO) is investigated using an ensemble set of Indian Ocean decoupling experiments (DCPL), utilizing a millennial integration of a coupled climate model. It is found that eliminating air–sea interactions over the Indian Ocean results in various degrees of ENSO amplification across DCPL simulations, with a shift in the underlying dynamics toward a more prominent thermocline mode. The DCPL experiments reveal that the net effect of the Indian Ocean in the control runs (CTRL) is a damping of ENSO. The extent of this damping appears to be negatively correlated to the coherence between ENSO and the Indian Ocean dipole (IOD). This type of relationship can arise from the long-lasting ENSO events that the model simulates, such that developing ENSO often coincides with Indian Ocean basin-wide mode (IOBM) anomalies during non-IOD years. As demonstrated via AGCM experiments, the IOBM enhances western Pacific wind anomalies that counteract the ENSO-enhancing winds farther east. In the recharge oscillator framework, this weakens the equatorial Pacific air–sea coupling that governs the ENSO thermocline feedback. Relative to the IOBM, the IOD is more conducive for ENSO growth. The net damping by the Indian Ocean in CTRL is thus dominated by the IOBM effect which is weaker with stronger ENSO–IOD coherence. The stronger ENSO thermocline mode in DCPL is consistent with the absence of any IOBM anomalies. This study supports the notion that the Indian Ocean should be viewed as an integral part of ENSO dynamics.

Indian Ocean Variability in the GFDL Coupled Climate Model

2007 ◽  
Vol 20 (13) ◽  
pp. 2895-2916 ◽  
Author(s):  
Qian Song ◽  
Gabriel A. Vecchi ◽  
Anthony J. Rosati
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Deep Convection ◽  
Warm Pool ◽  
Surface Winds ◽  
Pacific Warm Pool ◽  
El Niño Events ◽  
The Indian Ocean ◽  
El Nino Events

Abstract The interannual variability of the Indian Ocean, with particular focus on the Indian Ocean dipole/zonal mode (IODZM), is investigated in a 250-yr simulation of the GFDL coupled global general circulation model (CGCM). The CGCM successfully reproduces many fundamental characteristics of the climate system of the Indian Ocean. The character of the IODZM is explored, as are relationships between positive IODZM and El Niño events, through a composite analysis. The IODZM events in the CGCM grow through feedbacks between heat-content anomalies and SST-related atmospheric anomalies, particularly in the eastern tropical Indian Ocean. The composite IODZM events that co-occur with El Niño have stronger anomalies and a sharper east–west SSTA contrast than those that occur without El Niño. IODZM events, whether or not they occur with El Niño, are preceded by distinctive Indo-Pacific warm pool anomaly patterns in boreal spring: in the central Indian Ocean easterly surface winds, and in the western equatorial Pacific an eastward shift of deep convection, westerly surface winds, and warm sea surface temperature. However, delayed onsets of the anomaly patterns (e.g., boreal summer) are often not followed by IODZM events. The same anomaly patterns often precede El Niño, suggesting that the warm pool conditions favorable for both IODZM and El Niño are similar. Given that IODZM events can occur without El Niño, it is proposed that the observed IODZM–El Niño relation arises because the IODZM and El Niño are both large-scale phenomena in which variations of the Indo-Pacific warm pool deep convection plays a central role. Yet each phenomenon has its own dynamics and life cycle, allowing each to develop without the other. The CGCM integration also shows substantial decadal modulation of the occurrence of IODZM events, which is found to be not in phase with that of El Niño events. There is a weak, though significant, negative correlation between the two. Moreover, the statistical relationship between the IODZM and El Niño displays strong decadal variability.

The Influence of Atmospheric Convection on the Interaction between the Indian Ocean and ENSO

2017 ◽  
Vol 30 (24) ◽  
pp. 10155-10178 ◽  
Author(s):  
Claudia E. Wieners ◽  
Henk A. Dijkstra ◽  
Will P. M. de Ruijter
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Western Pacific ◽  
Water Volume ◽  
Maritime Continent ◽  
Enso Events ◽  
The Indian Ocean ◽  
The Western Pacific

In recent years it has been proposed that a negative (positive) Indian Ocean dipole (IOD) in boreal autumn favors an El Niño (La Niña) at a lead time of 15 months. Observational analysis suggests that a negative IOD might be accompanied by easterly anomalies over the western Pacific. Such easterlies can enhance the western Pacific warm water volume, thus favoring El Niño development from the following boreal spring onward. However, a Gill-model response to a negative IOD forcing would lead to nearly zero winds over the western Pacific. The authors hypothesize that a negative IOD—or even a cool western Indian Ocean alone—leads to low-level air convergence and hence enhanced convectional heating over the Maritime Continent, which in turn amplifies the wind convergence so as to cause easterly winds over the western Pacific. This hypothesis is tested by coupling an idealized Indian Ocean model and a convective feedback model over the Maritime Continent to the Zebiak–Cane model. It is found that, for a sufficiently strong convection feedback, a negative (positive) IOD indeed forces easterlies (westerlies) over the western Pacific. The contribution from the eastern IOD pole dominates. IOD variability is found to destabilize the El Niño–Southern Oscillation (ENSO) mode, whereas Indian Ocean basinwide warming (IOB) variability dampens ENSO, even in the presence of convection. The influence of the Indian Ocean on the spectral properties of ENSO is dominated by the IOB, while the IOD is a better predictor for individual ENSO events.

Impact of the barotropic tides on the seasonal Indonesian Throughflow 

2021 ◽  
Author(s):  
Oceane Richet ◽  
Bernadette Sloyan ◽  
Bea Pena-Molino ◽  
Maxim Nikurashin
Keyword(s):  
Indian Ocean ◽  
Thermohaline Circulation ◽  
Vertical Mixing ◽  
Warm Pool ◽  
Ocean Basin ◽  
Indonesian Throughflow ◽  
Indonesian Seas ◽  
Pacific Waters ◽  
The Indian Ocean ◽  
The Impact

<p>The Indonesian seas play a fundamental role in the coupled climate system, featuring the only tropical exchange between ocean basins in the global thermohaline circulation. The Indonesian Throughflow (ITF) carries Pacific Ocean warm pool waters through the Indonesian Seas, where they are cooled and freshened. The incoming Pacific waters are strongly modified via vertical mixing driven by numerous ocean processes and ocean-atmosphere fluxes. The result is a unique water mass that can be tracked across the Indian Ocean basin and beyond. With our high-resolution regional model of the Indonesian Seas, designed with the MITgcm, we focus our study on the impact of the barotropic tides on the ITF. In fact, the strong tides coming from the Pacific and Indian Oceans enter in the Indonesian Seas through narrow straits and interact with the complex topography of the region (sills, islands, deep seas). This interaction between the tides and the topography impacts directly the ITF by modifying the transport toward the Indian Ocean.</p>

scholarly journals Mixed diversity of shifting IOD and El Niño dominates the location of Maritime Continent autumn drought

2020 ◽  
Vol 7 (7) ◽  
pp. 1150-1153 ◽  
Author(s):  
Chundi Hu ◽  
Tao Lian ◽  
Ho-Nam Cheung ◽  
Shaobo Qiao ◽  
Zhenning Li ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Heat Source ◽  
El Niño ◽  
El Nino ◽  
Source Region ◽  
Warm Pool ◽  
Climate Variations ◽  
Maritime Continent ◽  
Pacific Warm Pool ◽  
Forest Wildfires

Summary The Maritime Continent is a huge heat source region over the Indo-Pacific warm pool and it plays a key role in global weather/climate variations. The locations of Maritime Continent autumn droughts, linked to frequent rampant forest wildfires, are closely related to the mixed diversity of El Niño and Indian Ocean Dipole events.

scholarly journals Glacial changes in tropical climate amplified by the Indian Ocean

2018 ◽  
Vol 4 (12) ◽  
pp. eaat9658 ◽  
Author(s):  
Pedro N. DiNezio ◽  
Jessica E. Tierney ◽  
Bette L. Otto-Bliesner ◽  
Axel Timmermann ◽  
Tripti Bhattacharya ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Climate Changes ◽  
Equatorial Indian Ocean ◽  
Walker Circulation ◽  
Warm Pool ◽  
Pacific Warm Pool ◽  
The Indian Ocean ◽  
The Tropics ◽  
The Last Glacial Maximum ◽  
The Last Glacial

The mechanisms driving glacial-interglacial changes in the climate of the Indo-Pacific warm pool are poorly understood. Here, we address this question by combining paleoclimate proxies with model simulations of the Last Glacial Maximum climate. We find evidence of two mechanisms explaining key patterns of ocean cooling and rainfall change interpreted from proxy data. Exposure of the Sahul shelf excites a positive ocean-atmosphere feedback involving a stronger surface temperature gradient along the equatorial Indian Ocean and a weaker Walker circulation—a response explaining the drier/wetter dipole across the basin. Northern Hemisphere cooling by ice sheet albedo drives a monsoonal retreat across Africa and the Arabian Peninsula—a response that triggers a weakening of the Indian monsoon via cooling of the Arabian Sea and associated reductions in moisture supply. These results demonstrate the importance of air-sea interactions in the Indian Ocean, amplifying externally forced climate changes over a large part of the tropics.

scholarly journals Impact of the April–May SAM on Central Pacific Ocean sea temperature over the following three seasons

2021 ◽  
Author(s):  
Ting Liu ◽  
Jianping Li ◽  
Cheng Sun ◽  
Tao Lian ◽  
Yazhou Zhang
Keyword(s):  
Indian Ocean ◽  
Cold Water ◽  
Southern Oscillation ◽  
Equatorial Pacific ◽  
Boreal Winter ◽  
Central Pacific ◽  
Sea Temperature ◽  
Easterly Wind ◽  
The Indian Ocean ◽  
The Impact

AbstractAlthough the impact of the extratropical Pacific signal on the El Niño–Southern Oscillation has attracted increasing concern, the impact of Southern Hemisphere Annular Mode (SAM)-related signals from outside the southern Pacific Basin on the equatorial sea temperature has received less attention. This study explores the lead correlation between the April–May (AM) SAM and central tropical Pacific sea temperature variability over the following three seasons. For the positive AM SAM case, the related simultaneous warm SST anomalies in the southeastern Indian Ocean favor significant regulation of vertical circulation in the Indian Ocean with anomalous ascending motion in the tropics. This can further enhance convection over the Marine Continent, which induces a significant horizontal Kelvin response and regulates the vertical Walker circulation. These two processes both result in the anomalous easterlies east of 130° E in the equatorial Pacific during AM. These easterly anomalies favor oceanic upwelling and eastward propagation of the cold water into the central Pacific. The cold water in turn amplifies the development of the easterly wind and further maintains the cold water into the boreal winter. The results presented here not only provide a possible link between extratropical climate variability in the Indian Ocean and climate variation in the equatorial Pacific, but also shed new light on the short-term prediction of tropical central Pacific sea temperature.

scholarly journals Seasonal and Interannual Variability of the Indo-Pacific Warm Pool and its Associated Climate Factors Based on Remote Sensing

2020 ◽  
Vol 12 (7) ◽  
pp. 1062 ◽  
Author(s):  
Zi Yin ◽  
Qing Dong ◽  
Fanping Kong ◽  
Dan Cao ◽  
Shuang Long
Keyword(s):  
Pacific Ocean ◽  
Indian Ocean ◽  
Time Scale ◽  
Warm Pool ◽  
Ocean Basin ◽  
The Pacific ◽  
Pacific Warm Pool ◽  
The Indian Ocean ◽  
The Pacific Ocean ◽  
Ocean Sector

With satellite observed Sea Surface Temperature (SST) accumulated for multiple decades, multi-time scale variabilities of the Indo-Pacific Warm Pool are examined and contrasted in this study by separating it into the Indian Ocean sector and the Pacific Ocean sector. Surface size, zonal center, meridional center, maximum SST and mean SST as the practical warm pool properties are chosen to investigate the warm pool variations for the period 1982–2018. On the seasonal time scale, the oscillation of the Indian Warm Pool is found much more vigorous than the Pacific Warm Pool on size and intensity, yet the interannual variabilities of the Indian Warm Pool and the Pacific Warm Pool are comparable. The Indian Warm Pool has weak interannual variations (3–5 years) and the Pacific Warm Pool has mighty interdecadal variations. The size, zonal movement and mean SST of the Indian Ocean Warm Pool (IW) are more accurate to depict the seasonal variability, and for the Pacific Ocean Warm Pool (PW), the size, zonal and meridional movements and maximum SST are more suitable. On the interannual scale, except for the meridional movements, all the other properties of the same basin have similar interannual variation signals. Following the correlation analysis, it turns out that the Indian Ocean basin-wide index (IOBW) is the most important contributor to the variabilities of both sectors. Lead-lag correlation results show that variation of the Pacific Ocean Warm Pool leads the IOBW and variation of the Indian Ocean Warm Pool is synchronous with the IOBW. This indicates that both sectors of the Indo-Pacific Warm Pool are significantly correlated with basin-wide warming or cooling.

scholarly journals The Curious Case of Indian Ocean Warming*,+

2014 ◽  
Vol 27 (22) ◽  
pp. 8501-8509 ◽  
Author(s):  
Mathew Koll Roxy ◽  
Kapoor Ritika ◽  
Pascal Terray ◽  
Sébastien Masson
Keyword(s):  
Indian Ocean ◽  
Southern Oscillation ◽  
Tropical Indian Ocean ◽  
Western Indian Ocean ◽  
Warming Trend ◽  
Warm Pool ◽  
Sea Surface ◽  
Monsoon Circulation ◽  
Mean Sea Surface ◽  
The Indian Ocean

Abstract Recent studies have pointed out an increased warming over the Indian Ocean warm pool (the central-eastern Indian Ocean characterized by sea surface temperatures greater than 28.0°C) during the past half-century, although the reasons behind this monotonous warming are still debated. The results here reveal a larger picture—namely, that the western tropical Indian Ocean has been warming for more than a century, at a rate faster than any other region of the tropical oceans, and turns out to be the largest contributor to the overall trend in the global mean sea surface temperature (SST). During 1901–2012, while the Indian Ocean warm pool went through an increase of 0.7°C, the western Indian Ocean experienced anomalous warming of 1.2°C in summer SSTs. The warming of the generally cool western Indian Ocean against the rest of the tropical warm pool region alters the zonal SST gradients, and has the potential to change the Asian monsoon circulation and rainfall, as well as alter the marine food webs in this biologically productive region. The current study using observations and global coupled ocean–atmosphere model simulations gives compelling evidence that, besides direct contribution from greenhouse warming, the long-term warming trend over the western Indian Ocean during summer is highly dependent on the asymmetry in the El Niño–Southern Oscillation (ENSO) teleconnection, and the positive SST skewness associated with ENSO during recent decades.

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