scholarly journals A Wall-like Sharp Downward Branch of the Walker Circulation above the Western Indian Ocean

2021 ◽  
Author(s):  
Tsubasa Kohyama ◽  
Tamaki Suematsu ◽  
Hiroaki Miura ◽  
Daisuke Takasuka
Keyword(s):  
Indian Ocean ◽  
Walker Circulation ◽  
Western Indian Ocean ◽  
The Walker Circulation

scholarly journals A Wall-like Sharp Downward Branch of the Walker Circulation above the Western Indian Ocean

2021 ◽  
Author(s):  
Tsubasa Kohyama ◽  
Tamaki Suematsu ◽  
Hiroaki Miura ◽  
Daisuke Takasuka
Keyword(s):  
Indian Ocean ◽  
Walker Circulation ◽  
Western Indian Ocean ◽  
The Walker Circulation

scholarly journals Changes in the Eastward Movement Speed of the Madden–Julian Oscillation with Fluctuation in the Walker Circulation

2021 ◽  
pp. 1-50
Author(s):  
Tamaki Suematsu ◽  
Hiroaki Miura
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Lower Boundary ◽  
Low Frequency ◽  
Walker Circulation ◽  
Movement Speed ◽  
Madden Julian Oscillation ◽  
Lower Boundary Condition ◽  
The Indian Ocean ◽  
The Walker Circulation

AbstractThe eastward movement of a convectively active region is a distinguishing characteristic of the Madden–Julian oscillation (MJO). However, knowledge about the mechanisms that determine the eastward movement speed remains limited. This study investigates how the background environment modulates the speed of the boreal winter MJO and describes an intrinsic relationship between the MJO and background atmospheric circulation. We calculated the speed of the MJO events from the daily tracking of the locations of the minimum values of the outgoing longwave radiation anomaly in the time–longitude space. These speeds were then used to analyze systematic differences in the sea surface temperature (SST) distribution associated with the MJO speed. The analysis revealed a deceleration of the MJO under low-frequency (> 90 days) SST distributions that increased toward the western Pacific from both the Indian Ocean and the eastern Pacific. In contrast, the dependency on SST variability in intraseasonal frequencies (20–90 days) was small. Subsequently, the relationship between the MJO speed and background circulation, which is largely determined by the lower boundary condition set by the low-frequency SST distribution, was analyzed. The analysis counterintuitively revealed that the MJO tends to decelerate when the large-scale zonal circulation with low-level westerlies and upper-level easterlies from the Indian Ocean to the Maritime Continents is strong. The results suggest a novel view that the MJO is an integral component of the Walker circulation and that its eastward movement is modulated by the state of the large-scale flow of the Walker circulation.

scholarly journals Remote Tropical Western Indian Ocean Forcing on Changes in June Precipitation in South China and the Indochina Peninsula

2020 ◽  
Vol 33 (17) ◽  
pp. 7553-7566 ◽  
Author(s):  
Marco Y.-T. Leung ◽  
Wen Zhou ◽  
Dongxiao Wang ◽  
P. W. Chan ◽  
S. M. Lee ◽  
...  
Keyword(s):  
Indian Ocean ◽  
South China ◽  
Walker Circulation ◽  
Tropical Indian Ocean ◽  
Western Indian Ocean ◽  
Warming Trend ◽  
Monsoon Trough ◽  
Indochina Peninsula ◽  
Warm Anomaly ◽  
Long Term Trends

AbstractIn this study, remote influence originating from the tropical western Indian Ocean on June precipitation in South China and the Indochina Peninsula is documented. Based on numerical simulation and statistical analysis, it is noted that the warm anomaly in the tropical western Indian Ocean can induce a weaker-than-normal Walker circulation across the tropical Indian Ocean and western Pacific Ocean. This further leads to a northeast–southwest-oriented western North Pacific subtropical high and a weaker-than-normal monsoon trough in the South China Sea. In addition, the weak monsoon trough is concurrent with an anomalous rising motion in South China and a sinking motion in the Indochina Peninsula. This enhances precipitation in South China and suppresses precipitation in the Indochina Peninsula on an interannual time scale. On the other hand, the warming trend in the tropical western Indian Ocean also supports the long-term trends of precipitation in the two regions.

scholarly journals Sharp Downward Branch of the Walker Circulation above the Indian Ocean

2020 ◽  
Author(s):  
Tsubasa Kohyama ◽  
Tamaki Suematsu ◽  
Hiroaki Miura
Keyword(s):  
Indian Ocean ◽  
Walker Circulation ◽  
The Indian Ocean ◽  
The Walker Circulation

scholarly journals Decadal Variability of Asian–Australian Monsoon–ENSO–TBO Relationships

2011 ◽  
Vol 24 (18) ◽  
pp. 4925-4940 ◽  
Author(s):  
Gerald A. Meehl ◽  
Julie M. Arblaster
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Walker Circulation ◽  
Climate System ◽  
Asia Pacific ◽  
Pacific Region ◽  
Trade Winds ◽  
Australian Monsoon ◽  
The Walker Circulation ◽  
Sst Anomalies

Abstract A set of dynamically coupled ocean–atmosphere mechanisms has previously been proposed for the Asia–Pacific tropics to produce a dominant biennial component of interannual variability [the tropospheric biennial oscillation (TBO)]. Namely, a strong Asian–Australian monsoon is often associated with negative SST anomalies in the equatorial eastern Pacific and a negative Indian Ocean dipole in northern fall between the strong Indian monsoon and strong Australian monsoon, and tends to be followed by a weak monsoon and positive SST anomalies in the Pacific the following year and so on. These connections are communicated through the large-scale east–west (Walker) circulation that involves the full depth of the troposphere. However, the Asia–Pacific climate system is characterized by intermittent decadal fluctuations whereby the TBO during some time periods is more pronounced than others. Observations and models are analyzed to identify processes that make the system less biennial at certain times due to one or some combination of the following:increased latitudinal extent of Pacific trade winds and wider cold tongue;warmer tropical Pacific compared to tropical Indian Ocean that weakens trade winds and reduces coupling strength;eastward shift of the Walker circulation;reduced interannual variability of Pacific and/or Indian Ocean SSTs. Decadal time-scale SST variability associated with the interdecadal Pacific oscillation (IPO) has been shown to alter the TBO over the Indo-Pacific region by contributing changes in either some or all of the four factors listed above. Analysis of a multicentury control run of the Community Climate System Model, version 4 (CCSM4), shows that this decadal modulation of interannual variability is transferred via the Walker circulation to the Asian–Australian monsoon region, thus affecting the TBO and monsoon–Pacific connections. Understanding these processes is important to be able to evaluate decadal predictions and longer-term climate change in the Asia–Pacific region.

scholarly journals Regional Patterns of Tropical Indo-Pacific Climate Change: Evidence of the Walker Circulation Weakening

2012 ◽  
Vol 25 (5) ◽  
pp. 1689-1710 ◽  
Author(s):  
Hiroki Tokinaga ◽  
Shang-Ping Xie ◽  
Axel Timmermann ◽  
Shayne McGregor ◽  
Tomomichi Ogata ◽  
...  
Keyword(s):  
Climate Change ◽  
Indian Ocean ◽  
General Circulation ◽  
Surface Wind ◽  
Circulation Model ◽  
Walker Circulation ◽  
Tropical Eastern Pacific ◽  
Maritime Continent ◽  
Regional Patterns ◽  
The Walker Circulation

Regional patterns of tropical Indo-Pacific climate change are investigated over the last six decades based on a synthesis of in situ observations and ocean model simulations, with a focus on physical consistency among sea surface temperature (SST), cloud, sea level pressure (SLP), surface wind, and subsurface ocean temperature. A newly developed bias-corrected surface wind dataset displays westerly trends over the western tropical Pacific and easterly trends over the tropical Indian Ocean, indicative of a slowdown of the Walker circulation. This pattern of wind change is consistent with that of observed SLP change showing positive trends over the Maritime Continent and negative trends over the central equatorial Pacific. Suppressed moisture convergence over the Maritime Continent is largely due to surface wind changes, contributing to observed decreases in marine cloudiness and land precipitation there. Furthermore, observed ocean mixed layer temperatures indicate a reduction in zonal contrast in the tropical Indo-Pacific characterized by larger warming in the tropical eastern Pacific and western Indian Ocean than in the tropical western Pacific and eastern Indian Ocean. Similar changes are successfully simulated by an ocean general circulation model forced with the bias-corrected wind stress. Whereas results from major SST reconstructions show no significant change in zonal gradient in the tropical Indo-Pacific, both bucket-sampled SSTs and nighttime marine air temperatures (NMAT) show a weakening of the zonal gradient consistent with the subsurface temperature changes. All these findings from independent observations provide robust evidence for ocean–atmosphere coupling associated with the reduction in the Walker circulation over the last six decades.

Editorial Introduction

2020 ◽  
Vol 4 (1) ◽  
pp. 1
Author(s):  
Editors of the JIOWS
Keyword(s):  
Nineteenth Century ◽  
Indian Ocean ◽  
Western Indian Ocean ◽  
Late Nineteenth Century ◽  
Fourth Volume ◽  
History Of ◽  
The Indian Ocean ◽  
Complex Relationships ◽  
Indian Ocean World ◽  
Shed Light

The editors are proud to present the first issue of the fourth volume of the Journal of Indian Ocean World Studies. This issue contains three articles, by James Francis Warren (Murdoch University), Kelsey McFaul (University of California, Santa Cruz), and Marek Pawelczak (University of Warsaw), respectively. Warren’s and McFaul’s articles take different approaches to the growing body of work that discusses pirates in the Indian Ocean World, past and present. Warren’s article is historical, exploring the life and times of Julano Taupan in the nineteenth-century Philippines. He invites us to question the meaning of the word ‘pirate’ and the several ways in which Taupan’s life has been interpreted by different European colonists and by anti-colonial movements from the mid-nineteenth century to the present day. McFaul’s article, meanwhile, takes a literary approach to discuss the much more recent phenomenon of Somali Piracy, which reached its apex in the last decade. Its contribution is to analyse the works of authors based in the region, challenging paradigms that have mostly been developed from analysis of works written in the West. Finally, Pawelczak’s article is a legal history of British jurisdiction in mid-late nineteenth-century Zanzibar. It examines one of the facets that underpinned European influence in the western Indian Ocean World before the establishment of colonial rule. In sum, this issue uses two key threads to shed light on the complex relationships between European and other Western powers and the Indian Ocean World.

scholarly journals Factors influencing microbial mat composition, distribution and dinitrogen fixation in three western Indian Ocean coral reefs

2012 ◽  
Vol 47 (1) ◽  
pp. 51-66 ◽  
Author(s):  
Loïc Charpy ◽  
Katarzyna A. Palinska ◽  
Raeid M. M. Abed ◽  
Marie José Langlade ◽  
Stjepko Golubic
Keyword(s):  
Indian Ocean ◽  
Coral Reefs ◽  
Western Indian Ocean ◽  
Dinitrogen Fixation ◽  
Microbial Mat ◽  
Composition Distribution ◽  
Factors Influencing
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