scholarly journals Relationship between Ural–Siberian Blocking and the East Asian Winter Monsoon in Relation to the Arctic Oscillation and the El Niño–Southern Oscillation

2012 ◽  
Vol 25 (12) ◽  
pp. 4242-4257 ◽  
Author(s):  
Ho Nam Cheung ◽  
Wen Zhou ◽  
Hing Yim Mok ◽  
Man Chi Wu
Keyword(s):  
Arctic Oscillation ◽  
East Asian Winter Monsoon ◽  
Southern Oscillation ◽  
Wave Train ◽  
East Asian ◽  
Winter Monsoon ◽  
The Arctic ◽  
Asian Winter Monsoon ◽  
Blocking Activity ◽  
The Arctic Oscillation

Abstract This study attempts to assess the possible linkage between Ural–Siberian blocking and the East Asian winter monsoon (EAWM). During the boreal winter, the dominance of blocking thermally enhances cold advection downstream. The frequent occurrence of Ural–Siberian blocking potentially promotes a cold EAWM and vice versa. The seasonal blocking activity can be regarded as the combined effect of the Arctic Oscillation (AO) and the El Niño–Southern Oscillation (ENSO). Weakened (strengthened) meridional flow in the positive (negative) phase of the AO is unfavorable (favorable) for the formation of blocking highs. Because the AO shows a close relationship with the North Atlantic Oscillation (NAO), its teleconnection with Ural–Siberian blocking may exist in the form of an eastward-propagating wave train. Be that as it may, the wave train signal across East Asia may be disturbed by the external effect of a strong ENSO event, which probably enhances (weakens) the westerlies near Siberia in its warm (cold) phase. Consequently, the blocking–EAWM relationship is stronger (weaker) when the AO and ENSO are in phase (out of phase). If both AO and ENSO attain the positive (negative) phase, the Siberian high tends to be weaker (stronger) and the temperature tends to be higher (lower) in East Asia, with less (more) Ural–Siberian blocking. On the other hand, if they are out of phase, they are not strongly linked to the intensity of the Siberian high, and the blocking activity over Ural–Siberia is unclear.

scholarly journals Distinct Modes of the East Asian Winter Monsoon

2006 ◽  
Vol 134 (8) ◽  
pp. 2165-2179 ◽  
Author(s):  
Bingyi Wu ◽  
Renhe Zhang ◽  
Rosanne D’Arrigo
Keyword(s):  
East Asia ◽  
Atmospheric Circulation ◽  
East Asian Winter Monsoon ◽  
Southern Oscillation ◽  
East Asian ◽  
Winter Monsoon ◽  
The Arctic ◽  
East Asian Trough ◽  
Siberian High ◽  
Asian Winter Monsoon

Abstract Two distinct modes of the East Asian winter monsoon (EAWM) have been identified, and they correspond to real and imaginary parts of the leading mode of the EAWM, respectively. Analyses of these modes used the National Centers for Environment Prediction (NCEP) and National Center for Atmospheric Research (NCAR) monthly mean reanalysis datasets for the period 1968–2003, as well as the Southern Oscillation index (SOI), North Atlantic Oscillation index, and eastern equatorial Pacific sea surface temperature (SST) data. Results were obtained by resolving a complex Hermite matrix derived from 850-hPa anomalous wind fields, and determining the resulting modes’ associations with several climate variables. The first distinct mode (M1) is characterized by an anomalous meridional wind pattern over East Asia and the western North Pacific. Mode M1 is closely related to several features of the atmospheric circulation, including the Siberian high, East Asian trough, East Asian upper-tropospheric jet, and local Hadley circulation over East Asia. Thus, M1 reflects the traditional EAWM pattern revealed in previous studies. The second distinct EAWM mode (M2), which was not identified previously, displays dominant zonal wind anomalies over the same area. Mode M2 exhibits a closer relation than M1 to sea level pressure anomalies over the northwestern Pacific southeast of Japan and with the SOI and equatorial eastern Pacific SST. Unlike M1, M2 does not show coherent relationships with the Siberian high, East Asian trough, and East Asian upper-tropospheric jet. Since atmospheric circulation anomalies relevant to M2 exhibit a quasi-barotropic structure, its existence cannot simply be attributed to differential land–sea heating. El Niño events tend to occur in the negative phase of M1 and the positive phase of M2, both corresponding to a weakened EAWM. The Arctic Oscillation does not appear to impact the EAWM on interannual time scales. Although the spatial patterns for the two modes are very different, the two distinct modes are complementary, with the leading EAWM mode being a linear combination of the two. The results herein therefore demonstrate that a single EAWM index may be inappropriate for investigating and predicting the EAWM.

scholarly journals An Intensity Index for the East Asian Winter Monsoon

2014 ◽  
Vol 27 (6) ◽  
pp. 2361-2374 ◽  
Author(s):  
Lin Wang ◽  
Wen Chen
Keyword(s):  
Indian Ocean ◽  
East Asia ◽  
East Asian Winter Monsoon ◽  
Southern Oscillation ◽  
East Asian ◽  
Tropical Indian Ocean ◽  
Winter Monsoon ◽  
The Arctic ◽  
Asian Winter Monsoon ◽  
The North

Abstract The thermal contrast between the Asian continent and the adjacent oceans is the primary aspect of the East Asian winter monsoon (EAWM) that can be well represented in the sea level pressure (SLP) field. Based on this consideration, a new SLP-based index measuring the intensity of the EAWM is proposed by explicitly taking into account both the east–west and the north–south pressure gradients around East Asia. The new index can delineate the EAWM-related circulation anomalies well, including the deepened (shallow) midtropospheric East Asian trough, sharpened and accelerated (widened and decelerated) upper-tropospheric East Asian jet stream, and enhanced (weakened) lower-tropospheric northerly winds in strong (weak) EAWM winters. Compared with previous indices, the new index has a very good performance describing the winter-mean surface air temperature variations over East Asia, especially for the extreme warm or cold winters. The index is strongly correlated with several atmospheric teleconnections including the Arctic Oscillation, the Eurasian pattern, and the North Pacific Oscillation/western Pacific pattern, implying the possible internal dynamics of the EAWM variability. Meanwhile, the index is significantly linked to El Niño–Southern Oscillation (ENSO) and the sea surface temperature (SST) over the tropical Indian Ocean. Moreover, the SST anomalies over the tropical Indian Ocean are more closely related to the index than ENSO as an independent predictor. This adds further knowledge to the prediction potentials of the EAWM apart from ENSO. The predictability of the index is high in the hindcasts of the Centre National de Recherches Météorologiques (CNRM) model from Development of a European Multimodel Ensemble System for Seasonal-to-Interannual Prediction (DEMETER). Hence, it would be a good choice to use this index for the monitoring, prediction, and research of the EAWM.

scholarly journals East Asian Winter Monsoon and Arctic Oscillation

2001 ◽  
Vol 28 (10) ◽  
pp. 2073-2076 ◽  
Author(s):  
Dao-Yi Gong ◽  
Shao-Wu Wang ◽  
Jin-Hong Zhu
Keyword(s):  
Arctic Oscillation ◽  
East Asian Winter Monsoon ◽  
East Asian ◽  
Winter Monsoon ◽  
Asian Winter Monsoon

Changes in the relationship between the East Asian winter monsoon and ENSO under global warming

2020 ◽  
Author(s):  
Zixuan Jia ◽  
Massimo Bollasina ◽  
Chaofan Li ◽  
Ruth Doherty ◽  
Oliver Wild
Keyword(s):  
Global Warming ◽  
East Asian Winter Monsoon ◽  
Southern Oscillation ◽  
East Asian ◽  
Winter Monsoon ◽  
Pacific Region ◽  
Anthropogenic Aerosols ◽  
Asian Winter Monsoon ◽  
Asian Pacific Region ◽  
Asian Pacific

<p>The East Asian winter monsoon (EAWM) is a prominent feature of the northern hemisphere atmospheric circulation during boreal winter, which has a large influence on weather and climate of the Asian-Pacific region. At interannual time scales, the strength of the EAWM is strongly influenced by the El Niño-Southern Oscillation (ENSO), while the ENSO-EAWM relationship displays pronounced interdecadal variations associated with changes in the ENSO teleconnection pathways to East Asia. Using future transient simulations from the Max Planck Institute-Grand Ensemble (MPI-GE), changes in the ENSO-EAWM relationship are examined at various global warming levels during the 21<sup>st</sup>-century. Results indicate that this relationship will enhance from present-day to +1.5°C, and then weaken until +3°C, strongly impacted by changes in anthropogenic forcing with internal variability playing a negligible role. The ENSO-EAWM relationship is strongly related to the background mean state of both the EAWM and ENSO under global warming. Both the climatological EAWM strength and the ENSO-related anomalies across the Asian-Pacific region contribute to changes in the ENSO-EAWM relationship. Furthermore, anthropogenic aerosols are also found to play a major role in influencing the ENSO-EAWM relationship under moderate warming (up to 1.5°C).</p>

scholarly journals Biases and Improvements of the ENSO- East Asian Winter Monsoon Teleconnection in CMIP5 and CMIP6 Models

2021 ◽  
Author(s):  
Wenping Jiang ◽  
Hainan Gong ◽  
Ping Huang ◽  
Lin Wang ◽  
Gang Huang ◽  
...  
Keyword(s):  
East Asian Winter Monsoon ◽  
Southern Oscillation ◽  
East Asian ◽  
Winter Monsoon ◽  
Western Pacific ◽  
Cmip5 Models ◽  
Northwest Pacific ◽  
Cold Tongue ◽  
Asian Winter Monsoon ◽  
Mean State

Abstract The influence of El Niño–Southern Oscillation (ENSO) on the East Asian winter monsoon (EAWM) is investigated based on the outputs of phase 6 of the Coupled Model Intercomparison Project (CMIP6) models and compared to that in phase 5 (CMIP5). Results show that the CMIP6 models generally reproduce the ENSO-EAWM teleconnection more realistically than the CMIP5 models, although they still somewhat underestimate the ENSO-EAWM teleconnection than observed. Based on the inter-model spread of ENSO-EAWM teleconnection simulated in the CMIP5/CMIP6 models, we reveal that the commonly underestimated ENSO-EAWM teleconnection among the models can be traced back to the excessive cold tongue bias in the equatorial western Pacific. A model with a stronger climatological cold tongue favors generating a more westward extension of the ENSO-related SST anomaly pattern, which in turn forces an anomalous cyclonic circulation over the Northwest Pacific (NWP). It offsets the anticyclonic anomalies in the NWP triggered by the warm ENSO-related SST anomalies in the tropical Indian Ocean and the central-eastern Pacific and weakens the ENSO-EAWM teleconnection. Compared with the CMIP5 models, CMIP6 models better simulate SST mean state and the resultant ENSO-EAWM teleconnection. The present results suggest that substantial efforts should be made to reduce the bias in the mean-state SST for further improving the simulation and projection of the East Asian-western Pacific winter climate.

scholarly journals On the Strengthened Relationship between the East Asian Winter Monsoon and Arctic Oscillation: A Comparison of 1950–70 and 1983–2012

2014 ◽  
Vol 27 (13) ◽  
pp. 5075-5091 ◽  
Author(s):  
Fei Li ◽  
Huijun Wang ◽  
Yongqi Gao
Keyword(s):  
Arctic Oscillation ◽  
East Asian Winter Monsoon ◽  
East Asian ◽  
Winter Monsoon ◽  
Arctic Sea Ice ◽  
Northern Eurasia ◽  
Tropical Region ◽  
Horizontal Structure ◽  
Near Surface ◽  
Asian Winter Monsoon

In this paper, the authors use NCEP reanalysis and 40-yr ECMWF Re-Analysis (ERA-40) data to document the strengthened relationship between the East Asian winter monsoon (EAWM) and winter Arctic Oscillation (AO) on the interannual time scale with a comparison of 1950–70 and 1983–2012. Their connection was statistically insignificant during 1950–70, whereas it was statistically significant during 1983–2012. The latter significant connection might be attributed to the East Asian jet stream (EAJS) upstream extension: the EAJS signal is relatively confined to the western North Pacific before the 1970s, whereas it extends westward toward East Asia after the 1980s. This upstream extension leads to the rearrangement of eastward-propagating Rossby waves with a much wider horizontal structure, thereby bonding the EAWM and the AO. Furthermore, the authors present observational evidence and model simulations demonstrating that the reduction of autumn Arctic sea ice cover (ASIC) is responsible for the strengthened EAWM–AO relationship after the 1980s by producing the EAJS upstream extension. After the 1980s, a strong anticyclonic anomaly over the polar ocean and anomalous easterly advection over northern Eurasia are generated by the near-surface heating over the Barents–Kara (B–K) Seas caused by the reduction of ASIC. This further induces cold anomalies over northern Eurasia, altering the meridional temperature gradient between the midlatitude and tropical region and consequently leading to westward penetration of the EAJS.

scholarly journals A Dynamical Index for the East Asian Winter Monsoon

2010 ◽  
Vol 23 (15) ◽  
pp. 4255-4262 ◽  
Author(s):  
Yueqing Li ◽  
Song Yang
Keyword(s):  
East Asia ◽  
East Asian Winter Monsoon ◽  
East Asian ◽  
Winter Monsoon ◽  
The Arctic ◽  
Tropospheric Temperature ◽  
Physical Processes ◽  
Asian Winter Monsoon ◽  
Monsoon Index ◽  
Wind Shears

Abstract A new index measuring the East Asian winter monsoon is defined using the mean wind shears of upper-tropospheric zonal wind based on the belief that the physical processes of both higher and lower latitudes, and at both lower and upper troposphere, should be considered to depict the variability of monsoon. When the index is high (low), the westerly jet is strong (weak), the East Asian trough is deep (shallow), the Siberian high is strong (weak), and anomalous low-level northerlies (southerlies) prevail over East Asia. As a result, the surface and lower-tropospheric temperature over East Asia decreases (increases) and the cold surges over Southeast Asia and tropical western Pacific are more (less) active. The index, which exhibits distinct interannual variations, is also strongly correlated with the Arctic Oscillation and Niño-3.4 sea surface temperature (SST) index. Compared to previous indexes, this index takes into account more influencing factors and better elucidates the physical processes associated with monsoon, enhancing interpretations of the variability of monsoon and its effects on regional weather and climate. Furthermore, the monsoon index is significantly linked to antecedent tropical Pacific SST and is highly predictable in the NCEP Climate Forecast System, indicating the advantage of the index for operational predictions of monsoon.

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