scholarly journals Extratropical Response to the MJO: Nonlinearity and Sensitivity to the Initial State

2018 ◽  
Vol 75 (1) ◽  
pp. 219-234 ◽  
Author(s):  
Hai Lin ◽  
Gilbert Brunet
Keyword(s):  
Indian Ocean ◽  
Wave Train ◽  
Circulation Model ◽  
Mirror Image ◽  
Western Pacific ◽  
Eastern Indian Ocean ◽  
Initial Condition ◽  
Initial State ◽  
Westerly Jet ◽  
The Western Pacific

Previous studies have shown that the Madden–Julian oscillation (MJO) has a global impact that may provide an important source of skill for subseasonal predictions. The extratropical response was found to be the strongest when the tropical diabatic heating has a dipole structure with convection anomaly centers of opposite sign in the eastern Indian Ocean and the western Pacific. A positive (negative) MJO dipole heating refers to that with heating (cooling) in the eastern Indian Ocean and cooling (heating) in the western Pacific. In this study, two aspects of the extratropical response to the MJO are examined: 1) nonlinearity, which answers the question of whether the response to a positive MJO dipole heating is the mirror image of that to a negative MJO, and 2) sensitivity to the initial state, which explores the dependence of the extratropical response on the initial condition of the westerly jet. Ensemble integrations using a primitive-equation global atmospheric circulation model are performed with anomalous tropical thermal forcings that resemble a positive MJO (+MJO) and a negative MJO (−MJO). The response in the first week is largely linear. After that, significant asymmetry is found between the response in the positive MJO and the negative MJO. The 500-hPa negative geopotential height response in the North Pacific of the −MJO run is located about 30° east of the positive height response of the +MJO run. There is also an eastward shift of the extratropical wave train in the Pacific–North American region. This simulated nonlinearity is in agreement with the observations. The two leading response patterns among the ensemble members are identified by an empirical orthogonal function (EOF) analysis. EOF1 represents an eastward shift of the wave train, which is positively correlated with strengthening of the East Asian subtropical upper-troposphere westerly jet in the initial condition. On the other hand, EOF2 represents an amplification of the response, which is associated with a southward shift of the westerly jet in the initial state.

scholarly journals Seasonality and Dynamics of Atmospheric Teleconnection from the Tropical Indian Ocean and the Western Pacific to West Antarctica

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 849
Author(s):  
Hyun-Ju Lee ◽  
Emilia-Kyung Jin
Keyword(s):  
Indian Ocean ◽  
Rossby Wave ◽  
Tropical Indian Ocean ◽  
Western Pacific ◽  
Tropical Region ◽  
Formation Mechanisms ◽  
West Antarctica ◽  
Background Flow ◽  
The Impact ◽  
The Western Pacific

The global impact of the tropical Indian Ocean and the Western Pacific (IOWP) is expected to increase in the future because this area has been continuously warming due to global warming; however, the impact of the IOWP forcing on West Antarctica has not been clearly revealed. Recently, ice loss in West Antarctica has been accelerated due to the basal melting of ice shelves. This study examines the characteristics and formation mechanisms of the teleconnection between the IOWP and West Antarctica for each season using the Rossby wave theory. To explicitly understand the role of the background flow in the teleconnection process, we conduct linear baroclinic model (LBM) simulations in which the background flow is initialized differently depending on the season. During JJA/SON, the barotropic Rossby wave generated by the IOWP forcing propagates into the Southern Hemisphere through the climatological northerly wind and arrives in West Antarctica; meanwhile, during DJF/MAM, the wave can hardly penetrate the tropical region. This indicates that during the Austral winter and spring, the IOWP forcing and IOWP-region variabilities such as the Indian Ocean Dipole (IOD) and Indian Ocean Basin (IOB) modes should paid more attention to in order to investigate the ice change in West Antarctica.

India and the Allure of the ‘Indo-Pacific’

2012 ◽  
Vol 49 (3-4) ◽  
pp. 165-188 ◽  
Author(s):  
David Scott
Keyword(s):  
Pacific Ocean ◽  
Indian Ocean ◽  
Think Tanks ◽  
Western Pacific ◽  
Eastern Indian Ocean ◽  
Western Pacific Ocean ◽  
Indian Government ◽  
The Us ◽  
Inherent Part

This article looks at the attraction that the term ‘Indo-Pacific’ has gained in strategic discourse in and around the Indian government since 2010. A strong geopolitical and geo-economic sense of the Indo-Pacific has become apparent in this emergent Indo-Pacific discourse, which combines elements of India’s ‘Look South’ and ‘Look East’ policies, and in which a core Indo-Pacific of the eastern Indian Ocean and western Pacific Ocean has particular strategic coherence. Not only have government leaders adopted the term Indo-Pacific at various times, diplomats, navy service chiefs, influential think tanks and persuasive voices like Shyam Saran and C. Raja Mohan have also been noticeable in their use of the term. India’s bilateral and trilateral relations with Japan, Australia and the US have attracted particular Indo-Pacific associations in India. While a criticism of the term Indo-Pacific is that it has negative China-centric, balancing undertones, the article finds that although China-centric balancing frequently accompanies Indo-Pacific discourse, this is not an inherent part of the concept.

scholarly journals Impacts of the Tropical Pacific–Indian Ocean Associated Mode on Madden–Julian Oscillation over the Maritime Continent in Boreal Winter

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1049
Author(s):  
Xin Li ◽  
Ming Yin ◽  
Xiong Chen ◽  
Minghao Yang ◽  
Fei Xia ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Kinetic Energy ◽  
Tropical Pacific ◽  
Western Pacific ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Madden Julian Oscillation ◽  
Maritime Continent ◽  
The Western Pacific ◽  
The Tropical Pacific

Based on the observation and reanalysis data, the relationship between the Madden–Julian Oscillation (MJO) over the Maritime Continent (MC) and the tropical Pacific–Indian Ocean associated mode was analyzed. The results showed that the MJO over the MC region (95°–150° E, 10° S–10° N) (referred to as the MC–MJO) possesses prominent interannual and interdecadal variations and seasonally “phase-locked” features. MC–MJO is strongest in the boreal winter and weakest in the boreal summer. Winter MC–MJO kinetic energy variation has significant relationships with the El Niño–Southern Oscillation (ENSO) in winter and the Indian Ocean Dipole (IOD) in autumn, but it correlates better with the tropical Pacific–Indian Ocean associated mode (PIOAM). The correlation coefficient between the winter MC–MJO kinetic energy index and the autumn PIOAM index is as high as −0.5. This means that when the positive (negative) autumn PIOAM anomaly strengthens, the MJO kinetic energy over the winter MC region weakens (strengthens). However, the correlation between the MC–MJO convection and PIOAM in winter is significantly weaker. The propagation of MJO over the Maritime Continent differs significantly in the contrast phases of PIOAM. During the positive phase of the PIOAM, the eastward propagation of the winter MJO kinetic energy always fails to move across the MC region and cannot enter the western Pacific. However, during the negative phase of the PIOAM, the anomalies of MJO kinetic energy over the MC is not significantly weakened, and MJO can propagate farther eastward and enter the western Pacific. It should be noted that MJO convection is more likely to extend to the western Pacific in the positive phases of PIOAM than in the negative phases. This is significant different with the propagation of the MJO kinetic energy.

Role of Abnormally Enhanced MJO over the Western Pacific in the Formation and Subseasonal Predictability of the Record-Breaking Northeast Asian Heatwave in the Summer of 2018

2020 ◽  
Vol 33 (8) ◽  
pp. 3333-3349 ◽  
Author(s):  
Pang-Chi Hsu ◽  
Yitian Qian ◽  
Yu Liu ◽  
Hiroyuki Murakami ◽  
Yingxia Gao
Keyword(s):  
Real Time ◽  
Time Scale ◽  
Wave Train ◽  
Northeast Asia ◽  
Warm Pool ◽  
Western Pacific ◽  
Western Pacific Warm Pool ◽  
Pacific Warm Pool ◽  
Northeast Asian ◽  
The Western Pacific

AbstractIn the summer of 2018, Northeast Asia experienced a heatwave event that broke the existing high-temperature records in several locations in Japan, the Korean Peninsula, and northeastern China. At the same time, an unusually strong Madden–Julian oscillation (MJO) was observed to stay over the western Pacific warm pool. Based on reanalysis diagnosis, numerical experiments, and assessments of real-time forecast data from two subseasonal-to-seasonal (S2S) models, we discovered the importance of the western Pacific MJO in the generation of this heatwave event, as well as its predictability at the subseasonal time scale. During the prolonged extreme heat period (11 July–14 August), a high pressure anomaly with variability at the intraseasonal (30–90 days) time scale appeared over Northeast Asia, causing persistent adiabatic heating and clear skies in this region. As shown in the composites of MJO-related convection and circulation anomalies, the occurrence of this 30–90-day high anomaly over Northeast Asia was linked with an anomalous wave train induced by tropical heating associated with the western tropical Pacific MJO. The impact of the MJO on the heatwave was further confirmed by sensitivity experiments with a coupled GCM. As the western Pacific MJO-related components were removed by nudging prognostic variables over the tropics toward their annual cycle and longer time scales (>90 days) in the coupled GCM, the anomalous wave train along the East Asian coast disappeared and the surface air temperature in Northeast Asia lowered. The MJO over the western Pacific warm pool also influenced the predictability of the extratropical heatwave. Our assessments of two S2S models’ real-time forecasts suggest that the extremity of this Northeast Asian heatwave can be better predicted 1–4 weeks in advance if the enhancement of MJO convection over the western Pacific warm pool is predicted well.

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.

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