scholarly journals The Role of the Local Hadley Circulation over the Western Pacific on the Zonally Asymmetric Anomalies over the Indian Ocean

2003 ◽  
Vol 81 (2) ◽  
pp. 259-276 ◽  
Author(s):  
Yoshiyuki KAJIKAWA ◽  
Tetsuzo YASUNARI ◽  
Ryuichi KAWAMURA
Keyword(s):  
Indian Ocean ◽  
Hadley Circulation ◽  
Western Pacific ◽  
The Indian Ocean ◽  
The Western Pacific

scholarly journals Convective activities associated with intraseasonal variation over Sumatera, Indonesia, observed with the equatorial atmosphere radar

2004 ◽  
Vol 22 (11) ◽  
pp. 3899-3916 ◽  
Author(s):  
T. H. Seto ◽  
M. K. Yamamoto ◽  
H. Hashiguchi ◽  
S. Fukao
Keyword(s):  
Indian Ocean ◽  
Active Phase ◽  
Western Pacific ◽  
Mountainous Area ◽  
Local Circulation ◽  
Intraseasonal Variation ◽  
Cloud Clusters ◽  
Inactive Phase ◽  
The Indian Ocean ◽  
The Western Pacific

Abstract. The influence of intraseasonal variation (ISV) on convective activities over Sumatera (or Sumatra) is studied by using data derived from the Equatorial Atmosphere Radar (EAR), the Boundary Layer Radar (BLR), the surface weather station, the Geostationary Meteorological Satellite (GMS), and NCEP/NCAR reanalysis. In June 2002, convective activities over the Indian Ocean, the maritime continent, and the western Pacific were significantly modulated by the ISV. Blackbody brightness temperature observed by GMS (TBB) showed that two super cloud clusters (SCCs) developed over the Indian Ocean (70-90° E) in the first half of June 2002, and propagated eastward from the Indian Ocean to the western Pacific. Convective activities were enhanced over the western Pacific (130-160° E) in the latter half of June 2002. Convergence at 1000hPa, which prevailed over the Indian Ocean in the first half of June 2002, propagated eastward to the western Pacific in the latter half of June 2002. Zonal wind observed by EAR and surface pressure observed at the observation site suggested the existence of a Kelvin-wave-like structure of ISV. From temporal variations of TBB, zonal wind at 850hPa, and vertical shear of horizontal wind between 700 and 150hPa, we classified the observation periods into the inactive phase (1-9 June), active phase (10-19 June), and postwesterly wind burst phase of ISV (20-26 June). During the inactive phase of ISV, convective activities caused by local circulation were prominent over Sumatera. Results of radar observations indicated the dominance of convective rainfall events over the mountainous area of Sumatera during the inactive phase of ISV. During the active phase of the ISV, cloud clusters (CCs), which developed in the convective envelope of SCC with a period of 1-2 days, mainly induced the formation of convective activities over Sumatera. Results of radar observations indicated that both convective and stratiform rainfall events occurred over the mountainous area of Sumatera during the active phase of ISV. In the postwesterly wind burst phase of ISV, convective activities were suppressed over Sumatera. Features of convective activities found over Sumatera generally agreed well with those found in Tropical Ocean and Global Atmosphere/Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). However, local circulation played an important role in the formation of convective activities over Sumatera in the inactive phase of ISV.

scholarly journals Impact of the Madden–Julian Oscillation on Summer Rainfall in Southeast China

2009 ◽  
Vol 22 (2) ◽  
pp. 201-216 ◽  
Author(s):  
Lina Zhang ◽  
Bizheng Wang ◽  
Qingcun Zeng
Keyword(s):  
Indian Ocean ◽  
Tropical Indian Ocean ◽  
Summer Rainfall ◽  
Western Pacific ◽  
Madden Julian Oscillation ◽  
Energy Propagation ◽  
Southeast China ◽  
The Indian Ocean ◽  
The Impact ◽  
The Western Pacific

Abstract The impact of the Madden–Julian oscillation (MJO) on summer rainfall in Southeast China is investigated using the Real-time Multivariate MJO (RMM) index and the observational rainfall data. A marked transition of rainfall patterns from being enhanced to being suppressed is found in Southeast China (east of 105°E and south of 35°N) on intraseasonal time scales as the MJO convective center moves from the Indian Ocean to the western Pacific Ocean. The maximum positive and negative anomalies of regional mean rainfall are in excess of 10% relative to the climatological regional mean. Such different rainfall regimes are associated with the corresponding changes in physical fields such as the western Pacific subtropical high (WPSH), moisture, and vertical motions. When the MJO is mainly over the Indian Ocean, the WPSH shifts farther westward, and the moisture and upward motions in Southeast China are increased. In contrast, when the MJO enters the western Pacific, the WPSH retreats eastward, and the moisture and upward motions in Southeast China are decreased. It is suggested that the MJO may influence summer rainfall in Southeast China through remote and local dynamical mechanisms, which correspond to the rainfall enhancement and suppression, respectively. The remote role is the energy propagation of the Rossby wave forced by the MJO-related heating over the Indian Ocean through the low-level westerly waveguide from the tropical Indian Ocean to Southeast China. The local role is the northward shift of the upward branch of the anomalous meridional circulation when the MJO is over the western Pacific, which causes eastward retreat of the WPSH and suppressed moisture transport toward Southeast China.

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.

scholarly journals Maritime Security and Geopolitics in the Indo-Pacific Region

2019 ◽  
Vol 18 (4) ◽  
pp. 71-86
Author(s):  
Gurpreet Singh Khurana
Keyword(s):  
Indian Ocean ◽  
National Security ◽  
Maritime Security ◽  
Western Pacific ◽  
Economic Power ◽  
Centre Of Gravity ◽  
Security Environment ◽  
The Us ◽  
The Indian Ocean ◽  
The Western Pacific

The centre-of-gravity of world‘s economic power is shifting eastwards to the ‗Indo-Pacific‘, a maritime-configured macro-region that spans the maritime underbelly of Asia connecting the Indian and the western Pacific oceans. The security environment in the Indian Ocean and the western Pacific are different; nonetheless, strong maritime security linkages emerging between the two oceans has led to the reincarnation of the concept of ‗Indo-Pacific‘. Since the turn of the 21st century, new maritime insecurities have taken root, including in terms of China‘s revisionist positions on the established maritime order. Notwithstanding the US response in the western Pacific and the recent articulation of its ‗Indo-Pacific‘ strategy, it is unclear how the regional countries and the major regional stakeholders willmanage to address the emerging maritime insecurities in the Indian Ocean, including in terms of China‘s expanding politico-military footprint. This paper attempts to examine the security environment and geopolitics in the Indo-Pacific in context of India‘s national security interests.

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