Different Enhancement of the East Asian Summer Monsoon under Global Warming and Interglacial Epochs Simulated by CMIP6 Models: Role of the Subtropical High

2020 ◽  
Vol 33 (22) ◽  
pp. 9721-9733
Author(s):  
Chao He ◽  
Wen Zhou
Keyword(s):  
Global Warming ◽  
Summer Monsoon ◽  
North Pacific ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Subtropical High ◽  
The Tibetan Plateau ◽  
Southerly Wind ◽  
Asian Summer

AbstractSoutherly wind in the lower troposphere is an essential feature of East Asian summer monsoon (EASM) circulation, which is reported to be enhanced under global warming scenarios and interglacial epochs. Based on an analysis of an ensemble of CMIP6 models, this study shows that the magnitude of intensification of the EASM circulation is much smaller under global warming scenarios than during interglacial epochs. Distinct changes in the western North Pacific subtropical high (WNPSH) are responsible for the different responses of the EASM circulation. The WNPSH is substantially enhanced during interglacial epochs, which acts to strengthen the southerly wind associated with the EASM on the western flank of the WNPSH. However, the change in the WNPSH is insignificant and cannot strengthen the EASM under global warming scenarios, and the weakly enhanced EASM circulation may be a direct response to intensified heating over the Tibetan Plateau. The land–ocean thermal contrast explains the different responses of the WNPSH. During interglacial epochs, the summertime surface warming over the subtropical North Pacific is much weaker than over Eurasia due to the large thermal inertia of the ocean to increased insolation, and the WNPSH is intensified as a response to the suppressed latent heating over the subtropical North Pacific. The fast response of the WNPSH to abrupt quadrupling of CO2 without sufficient ocean warming is an analog to the interglacial epochs, but it is offset by the effect of slow oceanic warming, resulting in an insignificant change of the WNPSH under global warming scenarios.

Spring Arctic Oscillation-East Asian summer monsoon connection through circulation changes over the western North Pacific

2011 ◽  
Vol 37 (11-12) ◽  
pp. 2199-2216 ◽  
Author(s):  
Dao-Yi Gong ◽  
Jing Yang ◽  
Seong-Joong Kim ◽  
Yongqi Gao ◽  
Dong Guo ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
North Pacific ◽  
East Asian Summer Monsoon ◽  
Western North Pacific ◽  
Arctic Oscillation ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Asian Summer ◽  
Circulation Changes

scholarly journals Interannual Seesaw between the Somali and the Australian Cross-Equatorial Flows and its Connection to the East Asian Summer Monsoon

2014 ◽  
Vol 27 (11) ◽  
pp. 3966-3981 ◽  
Author(s):  
Chen Li ◽  
Shuanglin Li
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Yellow River ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Significant Negative Correlation ◽  
Subtropical High ◽  
Yellow River Valley ◽  
Asian Summer

Abstract The correlations among the summer, low-level, cross-equatorial flows (CEFs) over the Indian–west Pacific Ocean region on the interannual time scale are investigated by using both the NCEP–NCAR reanalysis and 40-yr ECMWF Re-Analysis (ERA-40) datasets. A significant negative correlation (seesaw) has been illustrated between the Somali CEF and the three CEFs north of Australia (the South China Sea, Celebes Sea, and New Guinea; they are referred to in combination as the Australian CEF). A seesaw index is thus defined with a higher (lower) value representing an intensified (weakened) Somali CEF but a weakened (intensified) Australian CEF. The connection of the seesaw with the East Asian summer monsoon (EASM) is then investigated. The results suggest that an enhanced seesaw corresponds to an intensified EASM with more rainfall in north China, the Yellow River valley, and the upper reach of the Yangtze River. The seesaw reflects the opposite covariability between the two atmospheric action centers in the Southern Hemisphere, Mascarene subtropical high, and Australian subtropical high. Whether the seesaw–EASM connection is influenced by El Niño–Southern Oscillation (ENSO) or the Indian Ocean SST dipole mode (IOD) is analyzed. The results remain unchanged when the ENSO- or IOD-related signals are excluded, although ENSO exerts a significant influence. This implies an additional predictability for the EASM from the CEF seesaw.

scholarly journals Decadal Variations of the East Asian Summer Monsoon Forced by the 11-Year Insolation Cycle

2019 ◽  
Vol 32 (10) ◽  
pp. 2735-2745 ◽  
Author(s):  
Chunhan Jin ◽  
Jian Liu ◽  
Bin Wang ◽  
Mi Yan ◽  
Liang Ning
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Summer Monsoon ◽  
North Pacific ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Decadal Variation ◽  
Solar Forcing ◽  
Asian Summer

Statistical evidence suggests that solar activity may affect the atmospheric circulation over East Asia (EA), but the way in which the 11-yr solar radiation cycle affects the East Asian summer monsoon (EASM) remains unexplained. Based on one control experiment and four solar-only forcing experiments performed during the Community Earth System Model–Last Millennium Ensemble (CESM-LME) model project, we explore the potential impacts of the 11-yr solar cycle on EASM variability and the physical processes through which solar forcing influences EASM decadal variability. The model results show that the warm season [May–September (MJJAS)] mean precipitation over EA exhibits significant decadal variation with a “northern wet–southern dry” pattern during peak years in the strong 11-yr solar cycle epoch (AD 900–1285), which is in contrast to the absence of decadal signals during the weak 11-yr solar cycle epoch (AD 1400–1535). For the four-member ensemble averaged solar-only forcing experiment, the summer mean precipitation over northern EA is significantly correlated with the solar forcing ( r = 0.414, n = 68, p < 0.05) on a decadal time scale during the strong cycle epoch, whereas there is no statistical link between the EASM and solar activity during the weak cycle epoch ( r = 0.002, n = 24). A strong, 11-yr solar cycle is also shown to excite an anomalous sea surface temperature (SST) pattern that resembles a cool Pacific decadal oscillation (PDO) phase, which has a significant 11-yr periodicity. The associated anomalous North Pacific anticyclone dominates the entire extratropical North Pacific and enhances the southerly monsoon over EA, which results in abundant rainfall over northern EA. We argue that the 11-yr solar cycle affects the EASM decadal variation through excitation of a coupled decadal mode in the Asia–North Pacific region.

Sensitivity of East Asian summer monsoon precipitation to the location of the Tibetan Plateau

2021 ◽  
pp. 1-36
Author(s):  
Soo-Hyun Seok ◽  
Kyong-Hwan Seo
Keyword(s):  
Tibetan Plateau ◽  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
General Circulation ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Circulation Model ◽  
Dynamical Response ◽  
The Tibetan Plateau ◽  
Asian Summer

AbstractRecent studies have highlighted that a primary mechanism of the East Asian summer monsoon (EASM) is the fluid dynamical response to the Tibetan Plateau (TP), that is, orographically forced Rossby waves. With this mechanism in mind, this study explores how changes in the location of the TP affect the EASM precipitation. Specifically, the TP is moved in the four cardinal directions using idealized general circulation model experiments. The results show that the monsoon aspects are entirely determined by the location of the TP. Interestingly, the strongest EASM precipitation occurs when the TP is situated near its current location, a situation in which downstream southerlies are well developed from the surface to aloft. However, southerlies into the EASM region weaken as the TP moves, which in turn reduces the precipitation. Nevertheless, as long as it moves in the east–west direction, the TP is likely to force the stationary waves that induce precipitation over the mid-latitudes (not necessarily over East Asia). In contrast, moving the TP well north of its original location does not induce strong monsoon flows over the EASM region, resulting in the driest case. Meanwhile, although the southward movement of the TP triggers downstream southerlies to some extent, it does not lead to an increase in the precipitation. Overall, these results show that the location of the TP is crucial in determining the EASM precipitation, and the latter is much more sensitive to the displacement of the TP in the meridional direction than in the zonal direction.

The interaction of tropical and extratropical airmass controlling East Asian summer monsoon progression

2021 ◽  
Author(s):  
Ambrogio Volonté ◽  
Reinhard Schiemann ◽  
Andrew Turner ◽  
Pier Luigi Vidale
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Potential Temperature ◽  
The Tibetan Plateau ◽  
Primary Role ◽  
Air Masses ◽  
Multi Scale ◽  
Asian Summer

&lt;p&gt;China receives most of its rainfall during the East Asian summer monsoon (EASM). The EASM is a complex, multi-phase and multi-scale phenomenon, influenced by both tropical and mid-latitude dynamics and by the presence of major orography, such as the Tibetan Plateau. The EASM front, displaying a steep gradient in equivalent potential temperature, neatly separates tropical and extratropical air masses as the monsoon marches northwards, particularly in the &lt;em&gt;Mei Yu&lt;/em&gt; stage. Many questions are still open on the dynamics of EASM evolution. Recent work on the Indian monsoon has indicated a new approach, focusing on the interaction between competing air masses that shapes monsoon progression. Drawing from that approach, we apply Eulerian and Lagrangian methods to the ERA5 reanalysis dataset to provide a comprehensive study of the seasonal evolution of the EASM and of its front.&amp;#160;&lt;/p&gt;&lt;p&gt;A new frontal detection algorithm is used to perform a front-centred analysis of EASM evolution, allowing to clearly identify and depict the four main stages of evolution of the EASM, in agreement with recent studies. The dynamics of interaction between monsoon and mid-latitude air masses at the EASM front are then investigated, highlighting the key tropical and extratropical processes, at both upper and lower levels. The sub-tropical westerly jet (STWJ) over east Asia has a primary role in controlling the strength and the poleward progression of the EASM front, in particular during &lt;em&gt;Mei Yu&lt;/em&gt;. This upper-level mid-latitude forcing acts in conjunction with the low-level moist-air advection from the tropics, modulated by the seasonal cycle of the South Asian monsoon and by the location of the Western North Pacific subtropical high. The &lt;em&gt;Mei Yu&lt;/em&gt; stage is distinguished by an especially clear interaction between tropical and extratropical air masses that converge at the EASM front, with the importance of remote moisture sources for the advection of moist tropical air also highlighted. Composites of the years with highest and lowest latitude of the EASM front at &lt;em&gt;Mei Yu&lt;/em&gt; are also assessed, outlining the processes behind the interannual variability of the poleward progression of the EASM front. Their analysis reveals the influence of the STWJ on the strength of the mid-latitude flow impacting on the northern side of the EASM front. In turns, this affects the extent of the warm moist advection on the southern side and the distribution and intensity of resultant rainfall over China.&lt;/p&gt;&lt;p&gt;Thus, using a mix of diagnostics tools and methods of analysis, in this study we identify the key airmasses, and related processes, that characterise seasonal EASM progression and variability. Clarifying their roles and joint influences in the evolution of this complex, multi-scale and multi-stage phenomenon we also highlight the dynamics of the tropical-extratropical interaction that occurs at the front, particularly during its &lt;em&gt;Mei Yu&lt;/em&gt; northward migration.&lt;/p&gt;

Deficiencies and possibilities for long-lead coupled climate prediction of the Western North Pacific-East Asian summer monsoon

2010 ◽  
Vol 36 (5-6) ◽  
pp. 1173-1188 ◽  
Author(s):  
Sun-Seon Lee ◽  
June-Yi Lee ◽  
Kyung-Ja Ha ◽  
Bin Wang ◽  
Jae Kyung E. Schemm
Keyword(s):  
Summer Monsoon ◽  
North Pacific ◽  
East Asian Summer Monsoon ◽  
Western North Pacific ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Climate Prediction ◽  
Asian Summer

scholarly journals Can Global Warming Strengthen the East Asian Summer Monsoon?

2010 ◽  
Vol 23 (24) ◽  
pp. 6696-6705 ◽  
Author(s):  
Jianping Li ◽  
Zhiwei Wu ◽  
Zhihong Jiang ◽  
Jinhai He
Keyword(s):  
Global Warming ◽  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Eastern Asia ◽  
Position Change ◽  
The Past ◽  
Southward Shift ◽  
Asian Summer

Abstract The Indian summer monsoon (ISM) tends to be intensified in a global-warming scenario, with a weakened linkage with El Niño–Southern Oscillation (ENSO), but how the East Asian summer monsoon (EASM) responds is still an open question. This study investigates the responses of the EASM from observations, theoretical, and modeling perspectives. Observational and theoretical evidence demonstrates that, in contrast to the dramatic global-warming trend within the past 50 years, the regional-mean EASM rainfall is basically dominated by considerable interannual-to-decadal fluctuations, concurrent with enhanced precipitation over the middle and lower reaches of the Yangtze River and over southern Japan and suppressed rainfall amount over the South China and Philippine Seas. From 1958 through 2008, the EASM circulation exhibits a southward shift in its major components (the subtropical westerly jet stream, the western Pacific Ocean subtropical high, the subtropical mei-yu–baiu–changma front, and the tropical monsoon trough). Such a southward shift is very likely or in part due to the meridional asymmetric warming with the most prominent surface warming in the midhigh latitudes (45°–60°N), which induces a weakened meridional thermal contrast over eastern Asia. Another notable feature is the enhanced ENSO–EASM relationship within the past 50 years, which is opposite to the ISM. Fourteen state-of-the-art coupled models from the Intergovernmental Panel on Climate Change show that the EASM strength does not respond with any pronounced trend to the global-warming “A1B” forcing scenario (with an atmospheric CO2 concentration of 720 ppm) but shows interannual-to-decadal variations in the twenty-first century (2000–99). These results indicate that the primary response of the EASM to a warming climate may be a position change instead of an intensity change, and such position change may lead to spatial coexistence of floods and droughts over eastern Asia as has been observed in the past 50 years.

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