scholarly journals Distinct effects of winter monsoon and westerly circulation on dust aerosol transport over East Asia

2021 ◽  
Author(s):  
Liu Yang ◽  
Zhengguo Shi ◽  
Hui Sun ◽  
Xiaoning Xie ◽  
Xiaodong Liu ◽  
...  
Keyword(s):  
East Asia ◽  
Lower Layer ◽  
East Asian ◽  
Asian Dust ◽  
Winter Monsoon ◽  
Dust Aerosol ◽  
Tibet Plateau ◽  
Particle Sizes ◽  
Westerly Jet ◽  
Westerly Winds

Abstract The transport of dust aerosol in East Asia is affected by the East Asian winter monsoon (EAWM) and westerly circulation both for modern and geological periods. There are obvious seasonal changes in the intensity and range of EAWM and westerly jet; however, their impacts and relative contributions to East Asian dust transmission are still unclear. In this study, we use Regional Climate Model 4 (RegCM4) to simulate the changes in the East Asian dust cycle under present conditions, assessing the effects of EAWM and westerly jet on dust transport. The results show that the dust at the upper level is mainly transported by the westerly circulation, while that of the lower layer is mainly transported by the EAWM. In March, the westerly jet is located on the south side of the Tibet Plateau and the high-level dust aerosol is transmitted eastward to the northern Pacific. Low-level dust is transmitted to the southeastern China with the influence of EAWM. With the northward shift of the westerly jet, the control range of the westerly winds increases in May and their correlations are weakened. In contrary, the impact of EAWM on the lower layer dust is enhanced. Due to the strengthened interaction between the westerly winds and the EAWM, they can both affect the middle-level dust transmission. The effect of EAWM is sensitive to the dust particle sizes. Under the action of EAWM, fine-grained dust is transmitted far away, while coarse-grained dust is limited to the vicinity of the source area. Once the dust is carried to the westerly layer, the influence of westerly winds on the transmission of different particle sizes dust is similar.

scholarly journals Comparison of East Asian winter monsoon indices

2007 ◽  
Vol 10 ◽  
pp. 31-37 ◽  
Author(s):  
Keyword(s):  
East Asia ◽  
East Asian Winter Monsoon ◽  
East Asian ◽  
Summer Precipitation ◽  
Circulation Pattern ◽  
Winter Monsoon ◽  
Significance Level ◽  
Asian Winter Monsoon ◽  
Westerly Jet ◽  
Northwesterly Wind

Abstract. Four East Asian winter monsoon (EAWM) indices are compared in this paper. In the research periods, all the indices show similar interannual and decadal-interdecadal variations, with predominant periods centering in 3–4 years, 6.5 years and 9–15 years, respectively. Besides, all the indices show remarkable weakening trends since the 1980s. The correlation coefficient of each two indices is positive with a significance level of 99%. Both the correlation analyses and the composites indicate that in stronger EAWM years, the Siberian high and the higher-level subtropical westerly jet are stronger, and the Aleutian low and the East Asia trough are deeper. This circulation pattern is favorable for much stronger northwesterly wind and lower air temperature in the subtropical regions of East Asia, while it is on the opposite in weaker EAWM years. Besides, EAWM can also exert a remarkable leading effect on the summer monsoon. After stronger (weaker) EAWM, less (more) summer precipitation is seen over the regions from the Yangtze River valley of China to southern Japan, while more (less) from South China Sea to the tropical western Pacific.

scholarly journals Numerical Simulation of the Direct Radiative Effects of Dust Aerosol on the East Asian Winter Monsoon

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Hui Sun ◽  
Xiaodong Liu
Keyword(s):  
East Asian Winter Monsoon ◽  
East Asian ◽  
Northern China ◽  
Winter Monsoon ◽  
Dust Aerosol ◽  
Central China ◽  
The Tibetan Plateau ◽  
Asian Winter Monsoon ◽  
Radiation Change ◽  
Cooling Effects

Variations of the East Asian winter monsoon (EAWM) induced by dust aerosol are studied by using a regional climate model (RegCM4/Dust). Dust coupled and uncoupled experiments are carried out for the past decade (2000–2009). The coupled RegCM4 captures three centers of dust mixing ratio (DMR) located in the Taklamakan Desert, western Inner Mongolia, and northern Xinjiang, respectively, with maximum values greater than 500 µg kg−1in winter. The surface total radiation change induced by dust is negative, and its central value of −8 W m−2results in surface temperature cooling by 1.5°C in winter. Dust induced radiation change at the top of the atmosphere (TOA) is also negative in Northern China, except over the Tibetan Plateau (TP), and up to −5 W m−2in Central China. Dust cooling effects increase the sea level pressure (SLP) gradient between land and ocean, the cold surge frequency, and the East Asian jet stream (EAJ) intensity and then enhance the EAWM. The dry and cold wind pervade most areas of East Asia, suppressing large-scale precipitation and eventually leading to a rainfall decrease of about 10–30% in Northern China and the middle Yangtze River Valley.

scholarly journals Rapid transport of East Asian pollution to the deep tropics

2015 ◽  
Vol 15 (6) ◽  
pp. 3565-3573 ◽  
Author(s):  
M. J. Ashfold ◽  
J. A. Pyle ◽  
A. D. Robinson ◽  
E. Meneguz ◽  
M. S. M. Nadzir ◽  
...  
Keyword(s):  
East Asia ◽  
East Asian ◽  
Atmospheric Dispersion ◽  
Atmospheric Composition ◽  
Meridional Transport ◽  
Air Masses ◽  
The North ◽  
Westerly Winds ◽  
Modelling Environment ◽  
Cold Surges

Abstract. Anthropogenic emissions from East Asia have increased over recent decades. These increases have led to changes in atmospheric composition as far afield as North America under the prevailing westerly winds. Here we show that, during Northern Hemisphere (NH) winter, pollution originating in East Asia also directly affects atmospheric composition in the deep tropics. We present observations of marked intra-seasonal variability in the anthropogenic tracer perchloroethene (C2Cl4) collected at two locations in Borneo (117.84° E, 4.98° N and 118.00° E, 4.22° N) during the NH winter of 2008/2009. We use trajectories calculated with the Numerical Atmospheric-dispersion Modelling Environment to show that the observed enhancements in C2Cl4 mixing ratio are caused by rapid meridional transport, in the form of "cold surges", from the relatively polluted East Asian land mass. In these events air masses can move from ~35° N to Borneo in 4 days. We then present data from the Monitoring Atmospheric Composition and Climate reanalysis which suggest that air masses high in C2Cl4 may also contain levels of the pollutants carbon monoxide and ozone that are approximately double the typical "background" levels in Borneo. In addition to strengthening the meridional transport from the north, cold surges can enhance convection in Southeast Asia, and further trajectory calculations indicate that the polluted air masses can subsequently be lifted to the tropical upper troposphere. This suggests a potentially important connection between midlatitude pollution sources and the very low stratosphere.

The teleconnection between the Siberian snow-albedo feedback and the spring East Asian dust cycle : based on Last Millennium Ensemble

2020 ◽  
Author(s):  
Heng Liu
Keyword(s):  
East Asian ◽  
Lower Troposphere ◽  
Reanalysis Data ◽  
Asian Dust ◽  
Shortwave Radiation ◽  
Last Millennium ◽  
Albedo Feedback ◽  
Snow Albedo ◽  
The Past ◽  
Westerly Winds

<p>According to the reanalysis data of recent years, the Siberian snow-albedo feedback is found to play a crucial role on the spring East Asian dust cycle by influence local energy budget and circulation. By analyzing the CESM Last Millennium Ensemble conducted by National Center for Atmospheric Research (NCAR), we found that the spring East Asian dust burden is significantly correlated with the snow-albedo over Siberia during the past millennium. The correlation coefficient between the snow depth over Siberia and the East Asian dust burden reaches to 0.56. The cloud fraction over Siberia is also correlated with the dust burden with a coefficient of 0.40. The Siberian snow cover reflects shortwave radiation and cools down the lower and middle troposphere, which leads to more clouds and snows occurring over Siberia. The increased cloud cover therefore reflects more shortwave to cool down the surface as a positive feedback. The cooling of lower troposphere over Siberia induces cyclonic wind anomalies around the region, enhances the westerly winds over the East Asian deserts which locate on the south side of Siberia and finally promotes the East Asian dust cycle.</p>

scholarly journals Tree ring-based February–April temperature reconstruction for Changbai Mountain in Northeast China and its implication for East Asian Winter Monsoon

2009 ◽  
Vol 5 (2) ◽  
pp. 1215-1229
Author(s):  
H. F. Zhu ◽  
X. Q. Fang ◽  
X. M. Shao ◽  
Z. Y. Yin
Keyword(s):  
East Asia ◽  
Tree Ring ◽  
Northeast China ◽  
East Asian Winter Monsoon ◽  
East Asian ◽  
Temperature Reconstruction ◽  
Winter Monsoon ◽  
Changbai Mountain ◽  
Asian Winter Monsoon ◽  
Instrumental Period

Abstract. Long-term climatic records are scarce in the northeast Asia for understanding the behavior of the East Asian Winter Monsoon. Here we describe a 250-year February–April temperature reconstruction (TCBM) based on tree-ring widths of Korean Pines from the Changbai Mountain area, Northeast China. The reconstruction can account for 45.7% of the temperature variance in the instrumental period (1953 to 2001). Four cold events including 1784–1815, 1827–1851, 1878–1889 and 1911–1945, and two warm events of 1750–1783 and 1855–1877 were identified before the instrumental period. Four regime shifts were also detected at 1781, 1857, 1878 and 1989. Good agreements between TCBM and other temperature records of East Asia suggest that the reconstruction is of good reliability and captures the regional cold/warm events of East Asia. Moreover, TCBM shows negative correlations with the instrumental or proxy-based EAWM intensity records. The known weakening of the EAWM in the late 1980s is in agreement with the regime shift at 1989 in TCBM. These comparisons suggest that the February–April temperature reconstruction may be a good indicator of the EAWM intensity.

scholarly journals Quantifying the contribution of anthropogenic influence to the East Asian winter monsoon in 1960–2012

2019 ◽  
Author(s):  
Xin Hao ◽  
Shengping He ◽  
Huijun Wang ◽  
Tingting Han
Keyword(s):  
East Asia ◽  
Air Temperature ◽  
General Circulation ◽  
East Asian Winter Monsoon ◽  
East Asian ◽  
Surface Air Temperature ◽  
Winter Monsoon ◽  
Anthropogenic Influence ◽  
Anthropogenic Forcing ◽  
Asian Winter Monsoon

Abstract. The East Asian winter monsoon (EAWM) can be greatly influenced by many factors that can be classified as anthropogenic forcing and natural forcing. Here we explore the contribution of anthropogenic influence to the change in the EAWM over the past decades. Under all forcings observed during 1960–2013 (All-Hist run), the atmospheric general circulation model is able to reproduce the climatology and variability of the EAWM-related surface air temperature and 500 hPa geopotential height, and shows a statistically significant decreasing EAWM intensity with a trend coefficient of ∼−0.04 yr−1 which is close to the observed trend. By contrast, the simulation, which is driven by the same forcing as All-Hist run but with the anthropogenic contribution to them removed, shows no decreasing trend in the EAWM intensity. By comparing the simulations under two different forcing scenarios, we further reveal that the responses of the EAWM to the anthropogenic forcing include a rise of 0.6 ° in surface air temperature over the East Asia as well as weakening of the East Asia trough, which may result from the poleward expansion and intensification of the East Asian jet forced by the change of temperature gradient in the troposphere. Additionally, compared with the simulation without anthropogenic forcing, the frequency of strong (weak) EAWM occurrence is reduced (increased) by 45 % (from 0 to 10/7). These results indicate that the weakening of the EAWM during 1960–2013 may be mainly attributed to the anthropogenic influence.

scholarly journals Combined Effect of ENSO-Like and Atlantic Multidecadal Oscillation SSTAs on the Interannual Variability of the East Asian Winter Monsoon

2017 ◽  
Vol 30 (7) ◽  
pp. 2697-2716 ◽  
Author(s):  
Xin Hao ◽  
Shengping He
Keyword(s):  
Numerical Model ◽  
East Asia ◽  
Interannual Variability ◽  
East Asian Winter Monsoon ◽  
East Asian ◽  
Atlantic Multidecadal Oscillation ◽  
Winter Monsoon ◽  
Temperature Anomalies ◽  
Asian Winter Monsoon ◽  
Numerical Model Experiments

Using long-term observational data and numerical model experiments, this study found that the Atlantic multidecadal oscillation (AMO) affects the influence of ENSO-like sea surface temperature anomalies (SSTAs, which contain the variability of both El Niño–Southern Oscillation and Pacific decadal oscillation) on the interannual change in the East Asian winter monsoon (EAWM). In the observations, the out-of-phase relationship between the variations in ENSO and the EAWM was significantly intensified when the AMO and ENSO-like SSTAs were in phase. Warmer-than-normal winters occurred across East Asia when the ENSO-like SSTAs and AMO were positively in phase, with a significantly weakened Siberian high and anomalous anticyclones over the western North Pacific. The opposite patterns occurred under negative in-phase conditions. In contrast, when the ENSO-like and AMO SSTAs were out of phase, the anomalies related to the EAWM tended to exhibit relatively weaker features. Numerical model experiments confirmed these observational results. When the models were perturbed with warm ENSO-like SSTAs and warm AMO SSTAs, the atmosphere showed a weakened Siberian high, strong anticyclonic anomalies over the Philippine Sea, a weakened East Asian trough, and dominant positive temperature anomalies over East Asia, implying a weaker EAWM. Reverse responses to negative in-phase temperature anomalies were observed. However, the atmospheric signals that responded to the out-of-phase conditions were less robust. This phenomenon may be attributed to the superposition of the interannual variability of the EAWM caused by ENSO-like SSTAs upon the influence of AMO on background Eurasian climate and the Walker circulation response to the heating source provided by the AMO, which induced changes in ENSO-like variability through the surface wind anomalies and modulated the anomalous anticyclone/cyclone over the Philippine Sea in warm–cold ENSO-like events.

scholarly journals Potential Influence of Arctic Sea Ice to the Interannual Variations of East Asian Spring Precipitation*

2016 ◽  
Vol 29 (8) ◽  
pp. 2797-2813 ◽  
Author(s):  
Zhiwei Wu ◽  
Xinxin Li ◽  
Yanjie Li ◽  
Yun Li
Keyword(s):  
Sea Ice ◽  
East Asia ◽  
Wave Train ◽  
East Asian ◽  
Arctic Sea Ice ◽  
Interannual Variations ◽  
Spring Precipitation ◽  
Westerly Jet ◽  
Arctic Sea ◽  
Subtropical Westerly Jet

Abstract Arctic sea ice (ASI) and its potential climatic impacts have received increasing attention during the past decades, yet the relevant mechanisms are far from being understood, particularly how anomalous ASI affects climate in midlatitudes. The spring precipitation takes up as much as 30% of the annual total and significantly influences agriculture in East Asia. Here, observed evidence and numerical experiment results show that the ASI variability in the Norwegian Sea and the Barents Sea in the preceding winter is intimately connected with interannual variations of the East Asian spring precipitation (EAP). The former can explain about 14% of the total variance of the latter. The ASI anomalies persist from winter through the ensuing spring and excite downstream teleconnections of a distinct Rossby wave train prevailing over the Eurasian continent. For the reduced ASI, such a wave train pattern is usually associated with an anomalous low pressure center over the Mongolian plateau, which accelerates the East Asian subtropical westerly jet. The intensified subtropical westerly jet, concurrent with lower-level convergence and upper-level divergence, enhances the local convection and consequently favors rich spring precipitation over East Asia. For the excessive ASI, the situation tends to be opposite. Given that seasonal prediction of the EAP remains a challenging issue, the winter ASI variability may provide another potential predictability source besides El Niño–Southern Oscillation.

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