Is there interdecadal variation in the South Asian High?

2021 ◽  
pp. 1-46
Author(s):  
Dapeng Zhang ◽  
Yanyan Huang ◽  
BoTao Zhou ◽  
Huijun Wang
Keyword(s):  
South Asian ◽  
Geopotential Height ◽  
Yangtze River ◽  
North China ◽  
East Asian ◽  
Northwest Pacific ◽  
South Asian High ◽  
The Yangtze River ◽  
The South ◽  
Upper Troposphere

AbstractThe decadal intensification of the South Asian High (SAH) after the late 1970s, which is determined based on the geopotential height (H), is suspicious due to the lifting effect upon H caused by global warming. The updated reanalysis datasets of ERA5 and JRA55 indicate that the anticyclone in the upper troposphere over the Tibetan Plateau is relatively weak during 1980–2018 compared to that during 1950–1979. This decadal weakening of the SAH after 1979 can also be observed in the radiosonde observation data. Correspondingly, the SAH defined by eddy geopotential height (H’) reflects a consistent decadal weakening variation. The decadal weakening of SAH detected from H’ after the late 1970s matches with a decadal southward shift of the East Asian Westerly Jet, causing ascending motions over the Yangtze River Valley and descending motions over North China. Moreover, the decadal weakening and westward shift of the SAH is accompanied with the positive relative vorticity anomalies over the Northwest Pacific in the upper troposphere, which implies a declining and eastward shift of the western Pacific subtropical high (WPSH) and a weakened East Asian Summer Monsoon (EASM). Hence, the decadal weakening of the SAH after the late 1970s may contribute to the Yangtze-River-flooding-and-North-China-drought pattern through its connection with other circulation systems of EASM.

Impact of East Asian Summer Monsoon Heating on the Interannual Variation of the South Asian High

2015 ◽  
Vol 29 (1) ◽  
pp. 159-173 ◽  
Author(s):  
Pengfei Zhang ◽  
Yimin Liu ◽  
Bian He
Keyword(s):  
Middle East ◽  
South Asian ◽  
East Asian Summer Monsoon ◽  
Geopotential Height ◽  
Interannual Variation ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
South Asian High ◽  
Upper Troposphere ◽  
Asian Summer

Abstract Occupying the upper troposphere over subtropical Eurasia during boreal summer, the South Asian high (SAH) is thought to be a regulator of the East Asian summer monsoon (EASM), which is particularly important for regional climate over Asia. However, there is feedback of the condensational heating associated with EASM precipitation to SAH variability. In this study, interannual variation of SAH intensity and the mechanisms are investigated. For strong SAH cases, the high pressure system intensifies and expands. Significant positive anomalies of the geopotential height and upper-tropospheric temperature were found over the Middle East and to the east of the Tibetan Plateau (TP), namely, the western and the eastern flanks of the SAH. The dynamical diagnosis and the numerical experiments consistently show that the interannual variation of SAH intensity is strongly affected by EASM precipitation over the eastern TP–Yangtze River valley. The feedback of the condensational heating anomaly to the SAH is summarized as follows: Excessive EASM heating excites a local anticyclone in the upper troposphere and warms the upper troposphere, leading to the eastward extension of the SAH’s eastern edge and reinforcing geopotential height anomalies over East Asia. Furthermore, the monsoonal heating excites a westward-propagating Rossby wave that increases the upper-tropospheric geopotential height and warms the upper troposphere over the Middle East. In conclusion, this study suggests a mechanistic paradigm in which the EASM may also be a modulator of SAH variation rather than just a passive result of the latter as traditionally thought. The results suggest that the EASM and the SAH are a tightly interactive system.

scholarly journals Foreign influences on tropospheric ozone over East Asia through global atmospheric transport

2019 ◽  
Author(s):  
Han Han ◽  
Jane Liu ◽  
Huiling Yuan ◽  
Tijian Wang ◽  
Bingliang Zhuang ◽  
...  
Keyword(s):  
East Asia ◽  
South Asian ◽  
North American ◽  
Tropospheric Ozone ◽  
Surface Ozone ◽  
East Asian ◽  
South Asian High ◽  
Interannual Variations ◽  
Upper Troposphere ◽  
Strong Seasonality

Abstract. Tropospheric ozone in East Asia is influenced by the transport of ozone from foreign regions around the world. However, the magnitudes and variations of such influences remain unclear. This study was performed to investigate this influence and its variations with space and time using a global chemical transport model, GEOS-Chem, for emission zero-out and tagged ozone simulations. The results show that foreign ozone varies significantly with latitude, altitude, and season in the East Asian troposphere. The transport of foreign ozone to East Asia occurs primarily through the middle and upper troposphere, where the concentration of foreign ozone (32–65 ppbv) in East Asia is 0.5–6 times higher than that of native ozone (11–18 ppbv) and has strong seasonality, being largest in spring and lowest in winter. Foreign ozone in East Asia increases rapidly with altitude. At the surface, the annual average foreign ozone concentration is ~ 22.2 ppbv, which is comparable to its native counterpart of ~ 20.4 ppbv. The annual mean concentration of anthropogenic ozone from foreign regions is ~ 4.7 ppbv at the East Asian surface, and half of it comes from North America (1.3 ppbv) and Europe (1.0 ppbv). The presence of foreign ozone at the East Asian surface is highest in winter (27.1 ppbv) and lowest in summer (16.5 ppbv). This strong seasonality is largely modulated by the East Asian monsoon (EAM) via its influence on vertical motion. The large-scale subsidence prevailing during the East Asian winter monsoon (EAWM) favours the downdraft of foreign ozone to the surface, while widespread convection in the East Asian summer monsoon (EASM) blocks such transport. In summer, the South Asian High facilitates the build-up of South Asian ozone in the East Asian upper troposphere and constrains North American, European, and African ozone to the regions north of 35° N. The interannual variations of foreign ozone at the East Asian surface have been found to be closely related to the EAM. When the EAWM is strong, North American and European ozone are enhanced at the East Asian surface, as the subsidence behind the East Asian trough becomes stronger. In strong EASM years, South and Southeast Asian ozone is reduced at the East Asian surface due to weakened south-westerly monsoon wind. This study suggests substantial foreign influences on tropospheric ozone in East Asia and underscores the importance of the EAM in the seasonal and interannual variations of foreign influences on surface ozone in East Asia.

scholarly journals The Global Warming–Induced South Asian High Change and Its Uncertainty

2016 ◽  
Vol 29 (6) ◽  
pp. 2259-2273 ◽  
Author(s):  
Xia Qu ◽  
Gang Huang
Keyword(s):  
Global Warming ◽  
Indian Ocean ◽  
South Asian ◽  
Geopotential Height ◽  
General Circulation ◽  
South Asian High ◽  
Latent Heating ◽  
The South ◽  
Northern Indian Ocean ◽  
Circulation Change

Abstract Based on models from phase 5 of the Coupled Model Intercomparison Project (CMIP5), the present study investigates the South Asian high (SAH) change in response to global warming. Under global warming, the selected 16 coupled general circulation models all feature an elevation of geopotential height at 100 hPa to the south of the SAH climatological position; an easterly response is found over the northern Indian Ocean in all the models, while a westerly response is found over subtropical Asia. The ridges of the SAH shift equatorward in 75% of models. Using the linear baroclinic model, it is found that the combined effects of latent heating and the mean advection of stratification change (MASC) are mainly responsible for those responses. The MASC mainly leads to the aforementioned easterly and westerly responses; the latent heating contributes to the geopotential height response and the easterly response over the northern Indian Ocean. The most important intermodel diversity is found in the 100-hPa circulation change under global warming, accounting for more than half of the total intermodel variance. The intermodel spread of latent heating and the MASC are important factors in driving the 100-hPa circulation diversity. Furthermore, analysis shows that the projected uncertainties in humidity, vertical velocity, and global mean temperature change are the three most important sources of intermodel diversity for the 100-hPa circulation change.

Quasi‐Biweekly Oscillation of the South Asian High and Its Role in Connecting the Indian and East Asian Summer Rainfalls

2019 ◽  
Vol 46 (24) ◽  
pp. 14742-14750 ◽  
Author(s):  
Wei Wei ◽  
Renhe Zhang ◽  
Song Yang ◽  
Wenhong Li ◽  
Min Wen
Keyword(s):  
South Asian ◽  
East Asian ◽  
South Asian High ◽  
The South ◽  
Asian Summer

scholarly journals Connection between Anomalous Zonal Activities of the South Asian High and Eurasian Summer Climate Anomalies

2016 ◽  
Vol 29 (22) ◽  
pp. 8249-8267 ◽  
Author(s):  
Jian Shi ◽  
Weihong Qian
Keyword(s):  
South Asian ◽  
Surface Air Temperature ◽  
Northern China ◽  
Boreal Summer ◽  
South Asian High ◽  
The South ◽  
Climate Anomalies ◽  
Precipitation Anomalies ◽  
Air Column ◽  
Air Temperature Anomalies

Abstract Using the daily mean anomalies of atmospheric variables from the NCEP Reanalysis-1 (NCEP R1), this study reveals the connection between anomalous zonal activities of the South Asian high (SAH) and Eurasian climate anomalies in boreal summer. An analysis of variance identifies two major domains with larger geopotential height variability located in the eastern and western flanks of the SAH at around 100 and 150 hPa, respectively. For both eastern and western domains, extreme events are selected during 1981–2014 when normalized height anomalies are greater than 1.0 (less than −1.0) standard deviation for at least 10 consecutive days. Based on these events, four SAH modes that include strong and weak Tibetan modes (STM and WTM, respectively) and strong and weak Iranian modes (SIM and WIM, respectively) are defined to depict the zonal SAH features. The positive composite in the eastern (western) domain indicates the STM (SIM) manifests a robust wavelike pattern with an anomalous low at 150 hPa, and surface cold and wet anomalies over Mongolia and northern China (Kazakhstan and western Siberia) are surrounded by three anomalous highs at 150 hPa and surface warm and dry anomalies over Eurasia. Opposite distributions are also evident in the negative composites of the two domains (WTM and WIM). The surface air temperature anomalies are the downward extension of an anomalous air column aloft while the precipitation anomalies are directly associated with the height anomalies above the air column.

Economic Implications of Asian Integration

2008 ◽  
Vol 8 (3) ◽  
pp. 1850139 ◽  
Author(s):  
Joseph F. Francois ◽  
Ganeshan Wignaraja
Keyword(s):  
East Asia ◽  
South Asian ◽  
Regional Integration ◽  
East Asian ◽  
The South ◽  
Economic Implications ◽  
Spider Web ◽  
Integration Schemes ◽  
Asian Economies ◽  
Northeast Asian

The Asian countries are once again focused on options for large, comprehensive regional integration schemes. In this paper we explore the implications of such broad-based regional trade initiatives in Asia, highlighting the bridging of the East and South Asian economies. We place emphasis on the alternative prospects for insider and outsider countries. We work with a global general equilibrium model of the world economy, benchmarked to a projected 2017 sets of trade and production patterns. We also work with gravity-model based estimates of trade costs linked to infrastructure, and of barriers to trade in services. Taking these estimates, along with tariffs, into our CGE model, we examine regionally narrow and broad agreements, all centered on extending the reach of ASEAN to include free trade agreements with combinations of the northeast Asian economies (PRC, Japan, Korea) and also the South Asian economies. We focus on a stylized FTA that includes goods, services, and some aspects of trade cost reduction through trade facilitation and related infrastructure improvements. What matters most for East Asia is that China, Japan, and Korea be brought into any scheme for deeper regional integration. This matter alone drives most of the income and trade effects in the East Asia region across all of our scenarios. The inclusion of the South Asian economies in a broader regional agreement sees gains for the East Asian and South Asian economies. Most of the East Asian gains follow directly from Indian participation. The other South Asian players thus stand to benefit if India looks East and they are a part of the program, and to lose if they are not. Interestingly, we find that with the widest of agreements, the insiders benefit substantively in terms of trade and income while the aggregate impact on outside countries is negligible. Broadly speaking, a pan-Asian regional agreement would appear to cover enough countries, with a great enough diversity in production and incomes, to actually allow for regional gains without substantive third-country losses. However, realizing such potential requires overcoming a proven regional tendency to circumscribe trade concessions with rules of origin, NTBs, and exclusion lists. The more likely outcome, a spider web of bilateral agreements, carries with it the prospect of significant outsider costs (i.e. losses) both within and outside the region.

Identification of Yangtze River and Yellow River Paleochannels in South Yellow Sea Shelf

2013 ◽  
Vol 664 ◽  
pp. 27-31
Author(s):  
Zhao Jun Song ◽  
Jin Zhou ◽  
Qiao Chen ◽  
Zhen Kui Gu
Keyword(s):  
Continental Shelf ◽  
Yellow Sea ◽  
Yangtze River ◽  
Yellow River ◽  
River Sediments ◽  
The Yangtze River ◽  
South Yellow Sea ◽  
The South ◽  
Research Results ◽  
The South Yellow Sea

research of submarine paleochannels has not only a great significance in exploring the evolution of palaeoenvironment of continental shelf but also a practical application value in solving problems on disaster geology and environmental geology in the continental shelf development. Yellow River and Yangtze River both were concentrated in the northern Jiangsu to enter the South Yellow Sea Basin in the Last Glacial, playing an important role in the palaeoenvironment evolution of the South Yellow Sea. On the basis of integrating previous research results and researching a large number of shallow stratigraphic sections of paleochannels in the South Yellow Sea Shelf in detail, identification and research of Yangtze River and Yellow River paleochannels in the South Yellow Sea Shelf are carried out in this paper. Research results show that: the Yangtze River and Yellow River paleochannels in the South Yellow Sea continental shelf are significantly different in the river section, river pattern, major elements, as well as trace elements, clay minerals, carbonate content and heavy mineral assemblages in the river sediments and other aspects. These differences can be used as the evidence for identification of the Yangtze River and Yellow River paleochannels.

scholarly journals Provenance Shift during the Plio-Pleistocene in the Vertex of Yangtze Delta and Its Geomorphological Implications

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 996
Author(s):  
Junjie Yu ◽  
Wei Yue ◽  
Ping Liu ◽  
Bo Peng ◽  
Jie Zhang ◽  
...  
Keyword(s):  
Yangtze River ◽  
River Channel ◽  
Heavy Minerals ◽  
Tectonic Subsidence ◽  
Zircon Geochronology ◽  
The Yangtze River ◽  
Yangtze Delta ◽  
The South ◽  
Source To Sink ◽  
Regional Tectonic

One of the key issues of the Source-to-Sink process is revealing the geomorphological evolutions of large rivers from the perspective of river sink areas. This study aims to reveal the provenance change near the vertex of the Yangtze delta during the late Cenozoic and provide insight into the Yangtze channelization into the sea due to regional tectonic subsidence. Heavy minerals and zircon geochronology in the Plio-Pleistocene sediments of the vertex of the modern Yangtze delta (core RGK15) reveal that a significant provenance shift occurred at ~2.6 Ma (the beginning of the Pleistocene). During the Pliocene, ultra-stable heavy minerals and pre-Mesozoic zircon grains predominated in the sediments, probably derived from contemporary outcrops of sedimentary rock that were widely distributed in the delta and its surrounding area. They are completely different from those in the Pliocene sediments of the south delta, indicating that decentralized, local, small watersheds dominated the Yangtze delta during the Pliocene. This resulted from the relatively elevated terrain of this region due to the adjacent ancient Zhejiang–Fujian Uplift (ZFU) at that time. However, diversified heavy minerals and zircon geochronology similar to those of the modern upper Yangtze fingerprints occur in the Pleistocene sediments of core RGK15, implying that a significant provenance shift to the Yangtze River occurred here at ~2.6 Ma. The provenance shift recorded by the cores in the south delta mainly occurred at ~1.2 Ma, indicating that the Yangtze River channel was dragged southward with the further subsidence of the ancient Zhejiang–Fujian Uplift. This study reveals the southward migration process of the Yangtze River channel with the regional tectonic subsidence from the perspective of provenance evolution, which contributes to an understanding of when the Yangtze River channelized into the sea.

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