A Numerical Study on the Formation Mechanism of a Mesoscale Low during East-Asia Winter Monsoon

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.

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Comments on "Interannual variation of aerosol pollution in East Asia and its relation with strong/weak East Asian winter monsoon"

10.5194/acp-2017-500-rc3 ◽

2017 ◽

Author(s):

Anonymous

Keyword(s):

East Asia ◽

Interannual Variation ◽

East Asian Winter Monsoon ◽

East Asian ◽

Winter Monsoon ◽

Asian Winter Monsoon ◽

Aerosol Pollution

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

Climate of the Past Discussions ◽

10.5194/cpd-5-1215-2009 ◽

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.

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

10.5194/acp-2019-99 ◽

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.

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East Asia summer and winter monsoon evolution during the past 50 ka inferred from size-specific flux of mineral particles of the Lake Biwa sediment

Quaternary International ◽

10.1016/j.quaint.2012.08.1018 ◽

2012 ◽

Vol 279-280 ◽

pp. 345

Author(s):

Shigenobu Nagasawa

Keyword(s):

East Asia ◽

Lake Biwa ◽

Winter Monsoon ◽

The Past ◽

Mineral Particles

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

Journal of Climate ◽

10.1175/jcli-d-16-0118.1 ◽

2017 ◽

Vol 30 (7) ◽

pp. 2697-2716 ◽

Cited By ~ 14

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.

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Southward cold airmass flux associated with the East Asian winter monsoon: Diversity and impacts

Journal of Climate ◽

10.1175/jcli-d-20-0319.1 ◽

2021 ◽

pp. 1-37

Author(s):

Qian Liu ◽

Guixing Chen ◽

Lin Wang ◽

Yuki Kanno ◽

Toshiki Iwasaki

Keyword(s):

East Asia ◽

High Latitude ◽

Large Scale ◽

Southern China ◽

Temperature Drop ◽

Warming Trend ◽

Winter Monsoon ◽

Northeastern Asia ◽

Northerly Wind ◽

Low Latitudes

AbstractThe winter monsoon has strong impacts on East Asia via latitude-crossing southward cold airmass fluxes called cold air outbreaks (CAOs). CAOs have a high diversity in terms of meridional extent and induced weather. Using the daily cold airmass flux normalized at 50°N and 30°N during 1958–2016, we categorize the CAOs into three groups: high–middle (H–M), high–low (H–L) and middle–low (M–L) latitude events. The H–L type is found to have the longest duration, and the M–L type is prone to the strong CAOs regarding normalized intensity. The H–L and H–M events feature a large-scale dipole pattern of cold airmass flux over high-latitude Eurasia, and the former (latter) events feature relatively strong anticyclonic circulation over Siberia (cyclonic circulation over northeastern Asia). In contrast, the M–L events are characterized by a cyclonic anomaly over northeastern Asia but no obvious high-latitude precursor. The H–L events have the greatest coldness anomaly in airmasses near the surface, and the M–L events mainly feature a strong northerly wind. As a result, the H–L events induce widespread long-lasting low temperatures over East Asia, while the M–L events induce a sharp temperature drop at mainly low latitudes. Both H–L and M–L events coupling with the MJO enhance rainfall over the South China Sea, while H–M events increase rainfall over southern China. Moreover, the occurrences of H–L and M–L events experience a long-term decrease since the 1980s, which induce a stronger warming trend in the cold extremes than in the winter mean temperature at mid-low latitudes over East Asia.

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