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.

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>

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.

Influence of Global-Scale Variability on the Subtropical Ridge over Southeast Australia

2011 ◽  
Vol 24 (23) ◽  
pp. 6035-6053 ◽  
Author(s):  
Wenju Cai ◽  
Peter van Rensch ◽  
Tim Cowan
Keyword(s):  
Indian Ocean ◽  
Southern Oscillation ◽  
Climate Modes ◽  
Southeast Australia ◽  
The Indian Ocean ◽  
Wave Trains ◽  
The Impact ◽  
Austral Autumn ◽  
Subtropical Ridge

Abstract In recent decades, southeast Australia (SEA) has experienced a severe rainfall decline, with a maximum reduction in the austral autumn season. The cause(s) of this decline remain unclear. This study examines the interaction between remote large-scale climate modes and an atmospheric phenomenon known as the subtropical ridge (STR) at the local scale. A focus is placed on the utility of using the STR as a bridge for understanding how these remote climate drivers influence SEA rainfall through a response in local atmospheric conditions. Using observational data since 1979, it is found that a strong seasonality exists in the impact of the STR on SEA rainfall. In austral autumn, because SEA rainfall is poorly correlated with the STR intensity (STRI) and STR position (STRP) on an interannual basis, it follows that most of the autumn rainfall reduction cannot be explained by the STRI changes in this season. There is also no clear relationship between the autumn STR and known remote modes of variability. Reductions in SEA rainfall have occurred in the austral winter and spring seasons; however, neither is significant. During winter, although El Niño–Southern Oscillation (ENSO) has little impact on the STR, there is a significant influence from the Indian Ocean dipole (IOD) and the southern annular mode (SAM). The IOD impact is conducted through equivalent-barotropic Rossby wave trains stemming from the eastern Indian Ocean in response to the IOD-induced anomalous convection and divergence. These wave trains modify the intensity and position of the ridge over SEA. The impact from the SAM is similarly projected onto the STRI and STRP. The STR trend accounts for the entire observed decline in SEA winter rainfall, 80% of which is contributed by the upward trend of the IOD; the SAM exhibits virtually no trend over the 30-yr period in this season. In spring, SEA rainfall shows strong interannual variability and is well correlated with the STRI; the ridge itself is influenced by the IOD and ENSO but not by the SAM. The Indian Ocean is a major pathway for ENSO’s impact on SEA rainfall in this season, which is conducted by two wave trains emanating from the east and west poles of the IOD. These wave train patterns share an anomalously high surface pressure center south of Australia, which does not align with the STR over SEA. As such, only a small portion of the STRI variance is accounted for by fluctuations in ENSO and the IOD. Long-term changes in the STRI account for about 90% of the observed decline in SEA spring rainfall, all of which are due to a recent increased frequency in the number of positive IOD events (upward IOD trend); ENSO shows no long-term trend over the 30-yr period. In summary, variability and change in winter and spring rainfall across SEA can be understood through the impact of remote climate modes, such as ENSO, the IOD, and the SAM, on the STR. This approach, however, offers no utility for understanding what drives the long-term SEA autumn rainfall decline, the dynamics of which remain elusive.

scholarly journals Spatiotemporal Evolution and Determinant Factors of the Intra-Regional Trade Community Structures of the Indian Ocean Region

2021 ◽  
Vol 10 (4) ◽  
pp. 214
Author(s):  
Lihua Yuan ◽  
Xiaoqiang Chen ◽  
Changqing Song ◽  
Danping Cao ◽  
Hong Yi
Keyword(s):  
Indian Ocean ◽  
Explanatory Power ◽  
Community Structures ◽  
Indian Ocean Region ◽  
Spatiotemporal Evolution ◽  
Regional Trade ◽  
Determinant Factors ◽  
Ocean Region ◽  
The Indian Ocean ◽  
The Impact

The Indian Ocean Region (IOR) has become one of the main economic forces globally, and countries within the IOR have attempted to promote their intra-regional trade. This study investigates the spatiotemporal evolution of the community structures of the intra-regional trade and the impact of determinant factors on the formation of trade community structures of the IOR from 1996 to 2017 using the methods of social network analysis. Trade communities are groups of countries with measurably denser intra-trade ties but with extra-trade ties that are measurably sparser among different communities. The results show that the extent of trade integration and the trade community structures of the IOR changed from strengthening between 1996 and 2014 to weakening between 2015 and 2017. The largest explanatory power of the formation of the IOR trade community structures was the IOR countries’ economic size, indicating that market remained the strongest driver. The second-largest explanatory power was geographical proximity, suggesting that countries within the IOR engaged in intra-regional trade still tended to select geographically proximate trading partners. The third- and the fourth-largest were common civilization and regional organizational memberships, respectively. This indicates that sharing a common civilization and constructing intra-regional institutional arrangements (especially open trade policies) helped the countries within the IOR strengthen their trade communities.

scholarly journals Indian Ocean impact on ENSO evolution 2014–2016 in a set of seasonal forecasting experiments

2021 ◽  
Author(s):  
Michael Mayer ◽  
Magdalena Alonso Balmaseda
Keyword(s):  
Pacific Ocean ◽  
Indian Ocean ◽  
El Niño ◽  
Initial Conditions ◽  
El Nino ◽  
Southern Oscillation ◽  
Heat Content ◽  
Tropical Pacific ◽  
Decadal Variations ◽  
The Indian Ocean

AbstractThis study investigates the influence of the anomalously warm Indian Ocean state on the unprecedentedly weak Indonesian Throughflow (ITF) and the unexpected evolution of El Niño-Southern Oscillation (ENSO) during 2014–2016. It uses 25-month-long coupled twin forecast experiments with modified Indian Ocean initial conditions sampling observed decadal variations. An unperturbed experiment initialized in Feb 2014 forecasts moderately warm ENSO conditions in year 1 and year 2 and an anomalously weak ITF throughout, which acts to keep tropical Pacific ocean heat content (OHC) anomalously high. Changing only the Indian Ocean to cooler 1997 conditions substantially alters the 2-year forecast of Tropical Pacific conditions. Differences include (i) increased probability of strong El Niño in 2014 and La Niña in 2015, (ii) significantly increased ITF transports and (iii), as a consequence, stronger Pacific ocean heat divergence and thus a reduction of Pacific OHC over the two years. The Indian Ocean’s impact in year 1 is via the atmospheric bridge arising from altered Indian Ocean Dipole conditions. Effects of altered ITF and associated ocean heat divergence (oceanic tunnel) become apparent by year 2, including modified ENSO probabilities and Tropical Pacific OHC. A mirrored twin experiment starting from unperturbed 1997 conditions and several sensitivity experiments corroborate these findings. This work demonstrates the importance of the Indian Ocean’s decadal variations on ENSO and highlights the previously underappreciated role of the oceanic tunnel. Results also indicate that, given the physical links between year-to-year ENSO variations, 2-year-long forecasts can provide additional guidance for interpretation of forecasted year-1 ENSO probabilities.

scholarly journals The Impact of Parental Death on Child Well-being: Evidence from the Indian Ocean Tsunami

2013 ◽  
Author(s):  
Ava Cas ◽  
Elizabeth Frankenberg ◽  
Wayan Suriastini ◽  
Duncan Thomas
Keyword(s):  
Indian Ocean ◽  
Parental Death ◽  
Well Being ◽  
Indian Ocean Tsunami ◽  
The Indian Ocean ◽  
The Impact

scholarly journals Triggering the Indian Ocean Dipole from the Southern Hemisphere

2021 ◽  
Author(s):  
Lian-Yi Zhang ◽  
Yan Du ◽  
Wenju Cai ◽  
Zesheng Chen ◽  
Tomoki Tozuka ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Southern Hemisphere ◽  
Indian Ocean Dipole ◽  
Southern Oscillation ◽  
Southern Annular Mode ◽  
Triggering Mechanism ◽  
Phase Development ◽  
The Indian Ocean ◽  
High System ◽  
The Tropics

<p>This study identifies a new triggering mechanism of the Indian Ocean Dipole (IOD) from the Southern Hemisphere. This mechanism is independent from the El Niño/Southern Oscillation (ENSO) and tends to induce the IOD before its canonical peak season. The joint effects of this mechanism and ENSO may explain different lifetimes and strengths of the IOD. During its positive phase, development of sea surface temperature cold anomalies commences in the southern Indian Ocean, accompanied by an anomalous subtropical high system and anomalous southeasterly winds. The eastward movement of these anomalies enhances the monsoon off Sumatra-Java during May-August, leading to an early positive IOD onset. The pressure variability in the subtropical area is related with the Southern Annular Mode, suggesting a teleconnection between high-latitude and mid-latitude climate that can further affect the tropics. To include the subtropical signals may help model prediction of the IOD event.</p>

scholarly journals An integrated social response to disasters: the case of the Indian Ocean tsunami in Sri Lanka

2016 ◽  
Vol 25 (5) ◽  
pp. 595-610 ◽  
Author(s):  
Siri Hettige ◽  
Richard Haigh
Keyword(s):  
Sri Lanka ◽  
Indian Ocean ◽  
Disaster Recovery ◽  
Mode Of Delivery ◽  
Recovery Process ◽  
Qualitative Assessment ◽  
Indian Ocean Tsunami ◽  
Content Type ◽  
The Indian Ocean ◽  
The Impact

Purpose The impact of disasters caused by natural hazards on people in affected communities is mediated by a whole range of circumstances such as the intensity of the disaster, type and nature of the community affected and the nature of loss and displacement. The purpose of this paper is to demonstrate the need to adopt a holistic or integrated approach to assessment of the process of disaster recovery, and to develop a multidimensional assessment framework. Design/methodology/approach The study is designed as a novel qualitative assessment of the recovery process using qualitative data collection techniques from a sample of communities affected by the Indian Ocean tsunami in Eastern and Southern Sri Lanka. Findings The outcomes of the interventions have varied widely depending on such factors as the nature of the community, the nature of the intervention and the mode of delivery for donor support. The surveyed communities are ranked in terms of the nature and extent of recovery. Practical implications The indices of recovery developed constitute a convenient tool of measurement of effectiveness and limitations of external interventions. The assessment used is multidimensional and socially inclusive. Originality/value The approach adopted is new to post-disaster recovery assessments and is useful for monitoring and evaluation of recovery processes. It also fits into the social accountability model as the assessment is based on community experience with the recovery process.

scholarly journals The Linear Sensitivity of the North Atlantic Oscillation and Eddy-Driven Jet to SSTs

2019 ◽  
Vol 32 (19) ◽  
pp. 6491-6511 ◽  
Author(s):  
Hugh S. Baker ◽  
Tim Woollings ◽  
Chris E. Forest ◽  
Myles R. Allen
Keyword(s):  
Indian Ocean ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
High Sensitivity ◽  
Internal Variability ◽  
The North ◽  
The Indian Ocean ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
The Impact

Abstract The North Atlantic Oscillation (NAO) and eddy-driven jet contain a forced component arising from sea surface temperature (SST) variations. Due to large amounts of internal variability, it is not trivial to determine where and to what extent SSTs force the NAO and jet. A linear statistical–dynamic method is employed with a large climate ensemble to compute the sensitivities of the winter and summer NAO and jet speed and latitude to the SSTs. Key regions of sensitivity are identified in the Indian and Pacific basins, and the North Atlantic tripole. Using the sensitivity maps and a long observational SST dataset, skillful reconstructions of the NAO and jet time series are made. The ability to skillfully forecast both the winter and summer NAO using only SST anomalies is also demonstrated. The linear approach used here allows precise attribution of model forecast signals to SSTs in particular regions. Skill comes from the Atlantic and Pacific basins on short lead times, while the Indian Ocean SSTs may contribute to the longer-term NAO trend. However, despite the region of high sensitivity in the Indian Ocean, SSTs here do not provide significant skill on interannual time scales, which highlights the limitations of the imposed SST approach. Given the impact of the NAO and jet on Northern Hemisphere weather and climate, these results provide useful information that could be used for improved attribution and forecasting.

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