Intraseasonal Teleconnection between the Summer Eurasian Wave Train and the Indian Monsoon*

2007 ◽  
Vol 20 (15) ◽  
pp. 3751-3767 ◽  
Author(s):  
Qinghua Ding ◽  
Bin Wang
Keyword(s):  
High Pressure ◽  
Central Asia ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Wave Train ◽  
Intraseasonal Variability ◽  
The Other ◽  
Vertical Shear ◽  
Central Asian ◽  
Northeastern Atlantic

Abstract This study investigated the most recurrent coupled pattern of intraseasonal variability between midlatitude circulation and the Indian summer monsoon (ISM). The leading singular vector decomposition (SVD) pattern reveals a significant, coupled intraseasonal variation between a Rossby wave train across the Eurasian continent and the summer monsoon convection in northwestern India and Pakistan (hereafter referred to as NISM). The wave train associated with an active phase of NISM rainfall displays two high pressure anomalies, one located over central Asia and the other over northeastern Asia. They are accompanied by increased rainfall over the western Siberia plain and northern China and decreased rainfall over the eastern Mediterranean Sea and southern Japan. The circulation of the wave train shows a barotropic structure everywhere except the anomalous central Asian high, located to the northwest of India, where a heat-induced baroclinic circulation structure dominates. The time-lagged SVD analysis shows that the midlatitude wave train originates from the northeastern Atlantic and traverses Europe to central Asia. The wave train enhances the upper-level high pressure and reinforces the convection over the NISM region; meanwhile, it propagates farther toward East Asia along the waveguide provided by the westerly jet. After an outbreak of NISM convection, the anomalous central Asian high retreats westward. Composite analysis suggests a coupling between the central Asian high and the convective fluctuation in the NISM. The significance of the midlatitude–ISM interaction is also revealed by the close resemblance between the individual empirical orthogonal functions and the coupled (SVD) modes of the midlatitude circulation and the ISM. It is hypothesized that the eastward and southward propagation of the wave train originating from the northeastern Atlantic contributes to the intraseasonal variability in the NISM by changing the intensity of the monsoonal easterly vertical shear and its associated moist dynamic instability. On the other hand, the rainfall variations over the NISM reinforce the variations of the central Asian high through the “monsoon–desert” mechanism, thus reenergizing the downstream propagation of the wave train. The coupling between the Eurasian wave train and NISM may be instrumental for understanding their interaction and can provide a way to predict the intraseasonal variations of the Indian summer monsoon and East Asian summer monsoon.

scholarly journals Linking Stochasticity of Convection to Large-Scale Vertical Velocity to Improve Indian Summer Monsoon Simulation in the NCAR CAM5

2018 ◽  
Vol 31 (17) ◽  
pp. 6985-7002 ◽  
Author(s):  
Yong Wang ◽  
Guang J. Zhang ◽  
Yiquan Jiang
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Large Scale ◽  
Intraseasonal Variability ◽  
Intraseasonal Oscillation ◽  
Central India ◽  
The Other ◽  
Onset Date ◽  
Global Circulation Models ◽  
Budget Analysis

The Plant–Craig (PC) stochastic convective parameterization scheme is modified by linking the stochastic generation of convective clouds to the change of large-scale vertical pressure velocity at 500 hPa with time so as to better account for the relationship between convection and the large-scale environment. Three experiments using the National Center for Atmospheric Research (NCAR) Community Atmosphere Model, version 5 (CAM5), are conducted: one with the default Zhang–McFarlane deterministic convective scheme, another with the original PC stochastic scheme, and a third with the modified PC stochastic scheme. Evaluation is focused on the simulation of the Indian summer monsoon (ISM), which is a long-standing challenge for all current global circulation models. Results show that the modified stochastic scheme better represents the annual cycle of the climatological mean rainfall over central India and the mean onset date of ISM compared to other simulations. Also, for the simulations of ISM intraseasonal variability for quasi-biweekly and 30–60-day modes, the modified stochastic parameterization produces more realistic propagation and magnitude, especially for the observed northeastward movement of the 30–60-day mode, for which the other two simulations show the propagation in the opposite direction. Causes are investigated through a moisture budget analysis. Compared to the other two simulations, the modified stochastic scheme with an appropriate representation of convection better represents the patterns and amplitudes of large-scale dynamical convergence and moisture advection and thus corrects the monsoon cycle associated with their covariation during the peaks and troughs of intraseasonal oscillation.

Circumglobal Teleconnection in the Northern Hemisphere Summer*

2005 ◽  
Vol 18 (17) ◽  
pp. 3483-3505 ◽  
Author(s):  
Qinghua Ding ◽  
Bin Wang
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
Summer Monsoon ◽  
North Pacific ◽  
Wave Train ◽  
The Other ◽  
The North ◽  
Central Asian ◽  
Circumglobal Teleconnection ◽  
The North Pacific

Abstract Analysis of the 56-yr NCEP–NCAR reanalysis data reveals a recurrent circumglobal teleconnection (CGT) pattern in the summertime midlatitude circulation of the Northern Hemisphere. This pattern represents the second leading empirical orthogonal function of interannual variability of the upper-tropospheric circulation. The CGT, having a zonal wavenumber-5 structure, is primarily positioned within a waveguide that is associated with the westerly jet stream. The spatial phases of CGT tend to lock to preferred longitudes. The geographically phase-locked patterns bear close similarity during June, August, and September, but the pattern in July shows shorter wavelengths in the North Pacific–North America sector. The CGT is accompanied by significant rainfall and surface air temperature anomalies in the continental regions of western Europe, European Russia, India, east Asia, and North America. This implies that the CGT may be a source of climate variability and predictability in the above-mentioned midlatitude regions. The CGT has significant correlations with the Indian summer monsoon (ISM) and El Niño–Southern Oscillation (ENSO). However, in normal ISM years the CGT–ENSO correlation disappears; on the other hand, in the absence of El Niño or La Niña, the CGT–ISM correlation remains significant. It is suggested that the ISM acts as a “conductor” connecting the CGT and ENSO. When the interaction between the ISM and ENSO is active, ENSO may influence northern China via the ISM and the CGT. Additionally, the variability of the CGT has no significant association with the Arctic Oscillation and the variability of the western North Pacific summer monsoon. The circulation of the wave train shows a barotropic structure everywhere except the cell located to the northwest of India, where a baroclinic circulation structure dominates. Two possible scenarios are proposed. The abnormal ISM may excite an anomalous west-central Asian high and downstream Rossby wave train extending to the North Pacific and North America. On the other hand, a wave train that is excited in the jet exit region of the North Atlantic may affect the west-central Asian high and, thus, the intensity of the ISM. It is hypothesized that the interaction between the global wave train and the ISM heat source may be instrumental in maintaining the boreal summer CGT.

Modulation of coupled modes of Tibetan Plateau heating and Indian Summer Monsoon on summer rainfall over Central Asia

2021 ◽  
pp. 1-54
Keyword(s):  
Water Vapor ◽  
Tibetan Plateau ◽  
Central Asia ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Diabatic Heating ◽  
Summer Rainfall ◽  
Hadley Cell ◽  
Vapor Transport ◽  
Water Vapor Transport

Abstract It has been suggested that summer rainfall over Central Asia (CA) is significantly correlated with the summer thermal distribution of the Tibetan Plateau (TP) and the Indian summer monsoon (ISM). However, relatively few studies have investigated their synergistic effects of different distribution. This study documents the significant correlations between precipitation in CA and the diabatic heating of TP and the ISM based on the results of statistical analysis and numerical simulation. Precipitation in CA is is dominated by two water vapor transport branches from the south which are related to the two primary modes of anomalous diabatic heating distribution related to the TP and ISM precipitation, that is, the “+-” dipole mode in the southeastern TP and the Indian subcontinent (IS), and the “+-+” tripole mode in the southeastern TP, the IS, and southern India. Both modes exhibit obvious mid-latitude Silk Road pattern (SRP) wave trains with cyclone anomalies over CA, but with different transient and stationary eddies over south Asia. The different locations of anomalous anticyclones over India govern two water vapor transport branches to CA, which are from the Arabian Sea and the Bay of Bengal. The water vapor flux climbs while being transported northward and can be transported to CA with the cooperation of cyclonic circulation. The convergent water vapor and ascending motion caused by cyclonic anomalies favor the precipitation in CA. Further analysis corroborates the negative South Indian Ocean Dipole (NSIOD) in February could affect the tripole mode distribution of TP heating and ISM via the atmospheric circulation, water vapor transport and an anomalous Hadley cell circulation. The results indicate a reliable prediction reference for precipitation in CA.

Kazakstan and the Rest of Central Asia: Fifteen Shades of Difference

1998 ◽  
Vol 26 (3) ◽  
pp. 573-579 ◽  
Author(s):  
Michael Rywkin
Keyword(s):  
Central Asia ◽  
Past History ◽  
The Other ◽  
Geographic Position ◽  
Central Asian ◽  
Soviet Central Asia ◽  
Central Asian Republics

Kazakstan is both part of former Soviet Central Asia and yet stands apart in many respects. Its geographic position, past history and present development are unique for the area. It is significant that Soviet-era writings treated Kazakstan distinctly from the other four Central Asian republics. This essay is devoted to these differences.

Buddhism and Islam: Past to Present Encounters and Interfaith Lessons

Numen ◽  
1995 ◽  
Vol 42 (2) ◽  
pp. 141-155 ◽  
Author(s):  
David Scott
Keyword(s):  
Central Asia ◽  
Social Action ◽  
The Other ◽  
The West ◽  
Common Concern ◽  
Se Asia ◽  
Central Asian ◽  
Political Perspective ◽  
Negative Images ◽  
Positive Images

AbstractThe paper deals with the encounter and ensuing responses that can be traced between Buddhism and Islam, during their centuries of contact across Asia (Anatolia, Iran, Central Asia, India), and more recently in the West. Within this panorama of history certain immediate overtly negative images of the other can be perceived in both traditions, manifested in terms of actions and literature. However some more positive images seem to have crystallised in Islam, particularly and significantly within the mystical Sufi streams that emerged in the East Iranian and Central Asian lands. Such historical patterns of confrontation, convergence and mysticism lead into the more modern second part of the study. A geographical-political perspective is first used, as the variations in their relationship in the various countries of SE Asia, and the British situation are noted. This is followed by a review of potential approaches between Islam and Buddhism in the current inter-faith dialogue arena. Whilst some doctrinal areas may be reconcilable (according to Cleary), it is primarily in other areas that more promising avenues of approach may be discerned. One is the area of ethics and social action on issues of common concern, as suggested by figures like Badawi, Gilliat, Askari and Vajiragnana. Another one is in contemplational areas of mysticism, as acknowledged by figures like Idries Shah. In both areas this can be echoed in greater clarity in the Christian-Buddhist dialogue. A further implication may be to bring out the need to view religions in functionalist and transformational terms, rather than culture bound doctrinal norms.

Nomad Migration in Central Asia

2007 ◽  
Author(s):  
KAZIM ABDULLAEV
Keyword(s):  
Central Asia ◽  
Second Century ◽  
The Other ◽  
Cultural Identities ◽  
Migration Routes ◽  
Central Asian ◽  
History Of ◽  
And Migration

This chapter examines the ethnic and cultural identities and migration routes of nomadic tribes in Central Asia. It explains that the migration of Central Asian nomads, particularly into Transoxiana, can be divided into two categories. One is the long trans-regional route ascribable to the migration of the Yuezhi tribe from the valley of Gansu to the territory north of the Oxus River, and the other is the local migration attributed to the tribes such as the Dahae, Sakaraules, and Appasiakes. The chapter suggests that the events which determined nomad migration are connected with the history of the northern and western borders of Han China in the second century BC.

scholarly journals Meridionally Extending Anomalous Wave Train over Asia During Breaks in the Indian Summer Monsoon

2019 ◽  
Vol 3 (3) ◽  
pp. 353-366 ◽  
Author(s):  
Uppara Umakanth ◽  
Ramesh K. Vellore ◽  
R. Krishnan ◽  
Ayantika Dey Choudhury ◽  
Jagat S. H. Bisht ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
General Circulation ◽  
Wave Train ◽  
Eastern China ◽  
Circulation Model ◽  
Cyclonic Circulation ◽  
The Arctic ◽  
Indian Landmass ◽  
Central Eastern

Abstract Anomalous interactions between the Indian summer monsoon (ISM) circulation and subtropical westerlies are known to trigger breaks in the ISM on subseasonal time-scales, characterised by a pattern of suppressed rainfall over central-north India, and enhanced rainfall over the foothills of the central–eastern Himalayas (CEH). An intriguing feature during ISM breaks is the formation of a mid-tropospheric cyclonic circulation anomaly extending over the subtropical and mid-latitude areas of the Asian continent. This study investigates the mechanism of the aforesaid Asian continental mid-tropospheric cyclonic circulation (ACMCC) anomaly using observations and simplified model experiments. The results of our study indicate that the ACMCC during ISM breaks is part of a larger meridional wave train comprising of alternating anticyclonic and cyclonic anomalies that extend poleward from the monsoon region to the Arctic. A lead–lag analysis of mid-tropospheric circulation anomalies suggests that the meridional wave-train generation is linked to latent heating (LH) anomalies over the CEH foothills, Indo-China, and the Indian landmass during ISM breaks. By conducting sensitivity experiments using a simplified global atmospheric general circulation model forced with satellite-derived three-dimensional LH, it is demonstrated that the combined effects of the enhanced LH over the CEH foothills and Indo-China and decreased LH over the Indian landmass during ISM breaks are pivotal for generating the poleward extending meridional wave train and the ACMCC anomaly. At the same time, the spatial extent of the mid-latitude cyclonic anomaly over Far-East Asia is also influenced by the anomalous LH over central–eastern China. While the present findings provide interesting insights into the role of LH anomalies during ISM breaks on the poleward extending meridional wave train, the ACMCC anomaly is found to have important ramifications on the daily rainfall extremes over the Indo-China region. It is revealed from the present analysis that the frequency of extreme rainfall occurrences over Indo-China shows a twofold increase during ISM break periods as compared to active ISM conditions.

scholarly journals The role of potential vorticity anomalies in the Somali Jet on Indian Summer Monsoon Intraseasonal Variability

2017 ◽  
Vol 50 (11-12) ◽  
pp. 4149-4169 ◽  
Author(s):  
P. Rai ◽  
M. Joshi ◽  
A. P. Dimri ◽  
A. G. Turner
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Potential Vorticity ◽  
Intraseasonal Variability ◽  
Somali Jet
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