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 Genesis of the South Asian High and Its Impact on the Asian Summer Monsoon Onset

2013 ◽  
Vol 26 (9) ◽  
pp. 2976-2991 ◽  
Author(s):  
Boqi Liu ◽  
Guoxiong Wu ◽  
Jiangyu Mao ◽  
Jinhai He
Keyword(s):  
South Asian ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Lower Troposphere ◽  
Monsoon Onset ◽  
South Asian High ◽  
The South ◽  
Subtropical Anticyclone ◽  
Summer Monsoon Onset ◽  
Asian Summer

Abstract The formation of the South Asian high (SAH) in spring and its impacts on the Asian summer monsoon onset are studied using daily 40-yr ECMWF Re-Analysis (ERA-40) data together with a climate-mean composite technique and potential vorticity–diabatic heating (PV–Q) analysis. Results demonstrate that, about 2 weeks before the Asian summer monsoon onset, a burst of convection over the southern Philippines produces a negative vorticity source to its north. The SAH in the upper troposphere over the South China Sea is then generated as an atmospheric response to this negative vorticity forcing with the streamline field manifesting a Gill-type pattern. Afterward, the persistent rainfall over the northern Indochinese peninsula causes the SAH to move westward toward the peninsula. Consequently, a trumpet-shaped flow field is formed to its southwest, resulting in divergence pumping and atmospheric ascent just over the southeastern Bay of Bengal (BOB). Near the surface, as a surface anticyclone is formed over the northern BOB, an SST warm pool is generated in the central–eastern BOB. This, together with SAH pumping, triggers the formation of a monsoon onset vortex (MOV) with strong surface southwesterly developed over the BOB. Enhanced air–sea interaction promotes the further development and northward migration of the MOV. Consequently, the wintertime zonal-orientated subtropical anticyclone belt in the lower troposphere splits, abundant water vapor is transported directly from the BOB to the subtropical continent, and heavy rainfall ensues; the atmospheric circulation changes from winter to summer conditions over the BOB and Asian summer monsoon onset occurs.

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.

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.

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.

scholarly journals Interannual Variation of the South Asian High and Its Relation with Indian and East Asian Summer Monsoon Rainfall

2015 ◽  
Vol 28 (7) ◽  
pp. 2623-2634 ◽  
Author(s):  
Wei Wei ◽  
Renhe Zhang ◽  
Min Wen ◽  
Baek-Jo Kim ◽  
Jae-Cheol Nam
Keyword(s):  
Latent Heat ◽  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Monsoon Rainfall ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Summer Monsoon Rainfall ◽  
South Asian High ◽  
Asian Summer ◽  
Asian Summer Monsoon Rainfall

Abstract A diagnostic analysis reveals that on the interannual time scale the southeast–northwest movement is a dominant feature of the South Asian high (SAH), and it is closely related to the Indian and East Asian summer monsoon rainfall. The southeastward (northwestward) shift of the SAH is closely related to less (more) Indian summer monsoon rainfall and more (less) rainfall in the Yangtze River valley (YRV) over the East Asian summer monsoon region. An anomalous AGCM is utilized to examine the effect of latent heat anomalies associated with the Asian summer monsoon rainfall on the SAH. The negative latent heat anomalies over the northern Indian Subcontinent associated with a weak Indian summer monsoon stimulates an anomalous cyclone to its northwest and an anticyclone to its northeast over the eastern Tibetan Plateau and eastern China in the upper troposphere, which is responsible for the east–west shift of the SAH and more rainfall in the YRV. The positive latent heat release associated with rainfall anomalies in the YRV excites a southward-located anticyclone over eastern China, exerting a feedback effect on the SAH and leading to a southeast–northwest shift of the SAH.

scholarly journals Trapping, chemistry and export of trace gases in the South Asian summer monsoon observed during CARIBIC flights in 2008

2015 ◽  
Vol 15 (5) ◽  
pp. 6967-7018 ◽  
Author(s):  
A. Rauthe-Schöch ◽  
A. K. Baker ◽  
T. J. Schuck ◽  
C. A. M. Brenninkmeijer ◽  
A. Zahn ◽  
...  
Keyword(s):  
South Asian ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Trace Gases ◽  
Particle Dispersion ◽  
Atmospheric Pollutants ◽  
South Asian Summer Monsoon ◽  
The South ◽  
Air Masses ◽  
Asian Summer

Abstract. The CARIBIC (Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrument Container) passenger aircraft observatory performed in situ measurements at 10–12 km altitude in the South Asian summer monsoon anticyclone between June and September 2008. These measurements enable us to investigate this atmospheric region, which so far has mostly been observed from satellites, using the broad suite of trace gases and aerosols measured by CARIBIC. Elevated levels of a range of atmospheric pollutants were recorded e.g. carbon monoxide, total reactive nitrogen oxides, aerosol particles and several volatile organic compounds. The measurements provide detailed information about the chemical composition of air in different parts of the monsoon anticyclone, particularly of ozone precursors. While covering a range of 3500 km inside the monsoon anticyclone, CARIBIC observations show remarkable consistency, i.e. with regular latitudinal patterns of trace gases during the entire monsoon period. Trajectory calculations indicate that these air masses originated mainly from South Asia and Mainland Southeast Asia. Using the CARIBIC trace gas and aerosol measurements in combination with the Lagrangian particle dispersion model FLEXPART we investigated the characteristics of monsoon outflow and the chemical evolution of air masses during transport. Estimated photochemical ages of the air were found to agree well with transport times from a source region east of 95° E. The photochemical ages of the air in the southern part of the monsoon anticyclone were consistently younger (less than 7 days) and the air masses mostly in an ozone forming chemical regime. In its northern part the air masses were older (up to 13 days) and had unclear ozone formation or destruction potential. Based on analysis of forward trajectories several receptor regions were identified. In addition to predominantly westward transport, we found evidence for efficient transport (within 10 days) to the Pacific and North America, particularly during June and September, and also of cross-tropopause exchange, which was strongest during June and July. Westward transport to Africa and further to the Mediterranean was the main pathway during July.

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