Distinct Modes of the East Asian Summer Monsoon*

Abstract Resolution of a complex Hermitian matrix derived from monthly mean 850-hPa wind fields during the summer season (June–August) from 1968 to 2004 revealed four different modes of East Asian summer monsoon (EASM) variability. The leading EASM mode, accounting for 19.6% of the variance, is characterized by two different modes (M11 and M12) or their combination. Both portray a closed cyclonic or anticyclonic circulation anomaly over the western North Pacific (WNP), South China Sea (SCS), and southeastern China; corresponding anomalous geopotential height fields show a wave train structure from the WNP across Japan, the Okhotsk Sea, and Alaska to North America. Thus, the leading EASM mode characterizes the teleconnection pattern of the WNP-EASM. The correlation between M11 (M12) and the dynamic index for the WNP-EASM is 0.85 (0.51). M11 has leading spectral peaks at 15 and 3 yr, whereas M12 displays a predominant peak at 2 yr. It is found that M11 has interdecadal variations, with the transition years being circa 1973 and 1989, respectively. M11 is closely related to air–sea interactions in the SCS and the northwestern Pacific, and its association with the convective heat source over the northwestern Pacific is secondary. In contrast, M12 is closely related to the tropical convective heat source rather than tropical western Pacific sea surface temperature (SST). The second EASM mode, accounting for 12.8% of the variance, is identified and characterized by two distinct and alternating modes or their linear combination (M21 and M22). One mode (M21) closely relates to the dual blocking high pattern detected in anomalous sea level pressure (SLP) and 500-hPa geopotential heights over the Ural Mountains and the Okhotsk Sea. The other (M22) corresponds to a dipole blocking anomaly in anomalous SLP and geopotential heights, with opposing anomalous centers in the south of Japan and the Korean peninsula, and the area between Lake Baikal and the Okhotsk Sea. M22 shows significant correlations with summer mean rainfall in southern and southeastern China. Thus, a single index of EASM is inappropriate for investigating and predicting the EASM.

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Changing character of rainfall in eastern China, 1951–2007

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1715386115 ◽

2018 ◽

Vol 115 (9) ◽

pp. 2016-2021 ◽

Cited By ~ 20

Author(s):

Jesse A. Day ◽

Inez Fung ◽

Weihan Liu

Keyword(s):

Summer Monsoon ◽

East Asian Summer Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Eastern China ◽

East China ◽

Northwestern Pacific ◽

Rain Event ◽

Asian Summer ◽

Rain Events

The topography and continental configuration of East Asia favor the year-round existence of storm tracks that extend thousands of kilometers from China into the northwestern Pacific Ocean, producing zonally elongated patterns of rainfall that we call “frontal rain events.” In spring and early summer (known as “Meiyu Season”), frontal rainfall intensifies and shifts northward during a series of stages collectively known as the East Asian summer monsoon. Using a technique called the Frontal Rain Event Detection Algorithm, we create a daily catalog of all frontal rain events in east China during 1951–2007, quantify their attributes, and classify all rainfall on each day as either frontal, resulting from large-scale convergence, or nonfrontal, produced by local buoyancy, topography, or typhoons. Our climatology shows that the East Asian summer monsoon consists of a series of coupled changes in frontal rain event frequency, latitude, and daily accumulation. Furthermore, decadal changes in the amount and distribution of rainfall in east China are overwhelmingly due to changes in frontal rainfall. We attribute the “South Flood–North Drought” pattern observed beginning in the 1980s to changes in the frequency of frontal rain events, while the years 1994–2007 witnessed an uptick in event daily accumulation relative to the rest of the study years. This particular signature may reflect the relative impacts of global warming, aerosol loading, and natural variability on regional rainfall, potentially via shifting the East Asian jet stream.

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Preliminary Study of Land–Sea Microphysics Associated with the East Asian Summer Monsoon Rainband and Its Application to GPM DPR

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-19-0059.1 ◽

2020 ◽

Vol 37 (7) ◽

pp. 1231-1249

Author(s):

Yun Zhang ◽

Zuhang Wu ◽

Lifeng Zhang ◽

Yanqiong Xie ◽

Yanbin Huang ◽

...

Keyword(s):

Summer Monsoon ◽

East Asian Summer Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Northwestern Pacific ◽

Dual Frequency ◽

Tropical Ocean ◽

Raindrop Size Distribution ◽

Asian Summer ◽

Raindrop Size

AbstractRaindrop size distribution (DSD) characteristics during the East Asian summer monsoon (EASM) were studied, using measurements from three OTT Particle Size Velocity (Parsivel) disdrometers in Nanjing, Chuzhou, and the northwestern Pacific (NWP), respectively. Western and eastern parts of the monsoon rainband were separated for a comparative study of the DSD variability. Along with disdrometer data, GPM Dual-Frequency Precipitation Radar (DPR), Fengyun-2E (FY-2E), MODIS, GPCP, ERA-Interim, and in situ radiosonde datasets are combined to illustrate the possible microphysical mechanisms for the significant DSD variability in two parts, in terms of convective intensity, cloud structure, and aerosol effects. The DSD characteristics of six rain-rate classes and two rainfall categories (convective and stratiform) were studied. The western part has larger mass-weighted mean diameter Dm while smaller normalized intercept log10(Nw) than the eastern part, and the convective clusters of the western part (land) could be identified more maritime-like than continental-like due to moisture transport from the tropical ocean, while that of the eastern part (sea) is between maritime-like and continental-like. Cross validation of GPM rainfall products are implemented based on surface disdrometer observations. DPR products manifest better performance over sea than land areas of the EASM rainband. Empirical Dm–Ze and Nw–Dm relations were also derived preliminarily to improve the GPM rain-retrieval algorithms in the EASM season.

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The Tropospheric Energy Budgets of two Heat Source Regions within the Southwest-East Asian Summer Monsoon System: the Arabian Desert Empty Quarter and the Qinghai-Xizang Plateau

Proceedings of International Symposium on the Qinghai-Xizang Plateau and Mountain Meteorology ◽

10.1007/978-1-935704-19-5_45 ◽

1986 ◽

pp. 777-818

Author(s):

Eric A. Smith

Keyword(s):

Heat Source ◽

Summer Monsoon ◽

East Asian Summer Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Energy Budgets ◽

Source Regions ◽

Monsoon System ◽

Xizang Plateau ◽

Asian Summer

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Numerical Modeling of Topography-Modulated Dust Aerosol Distribution and Its Influence on the Onset of East Asian Summer Monsoon

Advances in Meteorology ◽

10.1155/2016/6951942 ◽

2016 ◽

Vol 2016 ◽

pp. 1-15 ◽

Cited By ~ 2

Author(s):

Hui Sun ◽

Xiaodong Liu

Keyword(s):

Heat Source ◽

East Asia ◽

Summer Monsoon ◽

East Asian Summer Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Dust Aerosol ◽

Summer Monsoon Onset ◽

Aerosol Distribution ◽

Asian Summer

A regional climate model coupled with a dust module was used to simulate dust aerosol distribution and its effects on the atmospheric heat source over the TP, East Asian summer monsoon onset, and precipitation in East Asia modulated by the uplift of the northern TP. We carried out four experiments, including a modern (i.e., high-mountain) experiment with (HMD) and without (HM) the major deserts in Northwest China and a low-mountain experiment with (LMD) and without (LM) the deserts. The results show that dust greatly increases in the Taklamakan Desert accompanied with the uplift of the northern TP, and the increase exceeds 150 µg kg−1in spring. A strong cyclone in the Tarim Basin produced by the uplifted northern TP enhances dust emissions in the Taklamakan Desert in summer. Meanwhile, the dust loading over the TP also increases induced by the uplift of the northern TP, causing the heat source over the TP decreased. Under the condition of the northern TP uplift to present altitude, dust delays the East Asia summer monsoon onset by two pentads and one pentad, respectively, in the southern and northern monsoon regions and greatly suppresses precipitation in East Asia compared with results in the low terrain experiments.

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Orbital and Millennial Variations in Sea Ice in the Southwestern Okhotsk Sea Since the Last Interglacial Period and Their Implications

Frontiers in Earth Science ◽

10.3389/feart.2021.710797 ◽

2021 ◽

Vol 9 ◽

Author(s):

Anqi Wang ◽

Zhengquan Yao ◽

Xuefa Shi ◽

Kunshan Wang ◽

Jianjun Zou ◽

...

Keyword(s):

Sea Ice ◽

Summer Monsoon ◽

East Asian Summer Monsoon ◽

Arctic Oscillation ◽

Asian Summer Monsoon ◽

East Asian ◽

The Arctic ◽

Okhotsk Sea ◽

Asian Summer ◽

Millennial Scale

Sea ice in the Okhotsk Sea plays a significant role in global climate change. However, the history and mechanism of changes in sea ice spanning the last glacial cycle remain controversial. In this study, an 8.8 m core (LV55-40-1) was recovered from the southwestern Okhotsk Sea that contains a continuous sea ice record over the past ∼110 kyr. The sand fraction and dropstones were used as ice-rafted debris proxies to reconstruct the history of sea ice variations over the last ∼110 kyr and to determine the underlying causes on orbital and millennial timescales. Sea ice expansions occurred during MIS 5b, MIS 4, mid-MIS 3, and early MIS 1, which were controlled mainly by decreased autumn insolation on an orbital timescale. Superimposed on the orbital-scale changes, millennial-scale variations in sea ice were also observed, with 19 expansion events that coincided with cold Dansgaard-Oeschger stadials. Millennial scale sea ice variations were most likely controlled by both the Arctic oscillation and the East Asian summer monsoon. During periods of negative Arctic oscillation patterns, decreased air temperatures over the Okhotsk Sea caused more active sea ice formation. Such conditions could have been reinforced, by a reduced influence of warm advection at the surface of the Okhotsk Sea caused by decreased discharge from the Amur River that resulted from a weakened East Asian summer monsoon during cold stadials.

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Efficient transport of atmospheric microplastics onto the continent via the East Asian summer monsoon

Journal of Hazardous Materials ◽

10.1016/j.jhazmat.2021.125477 ◽

2021 ◽

Vol 414 ◽

pp. 125477

Author(s):

Xiaohui Wang ◽

Kai Liu ◽

Lixin Zhu ◽

Changjun Li ◽

Zhangyu Song ◽

...

Keyword(s):

Summer Monsoon ◽

East Asian Summer Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Asian Summer ◽

Efficient Transport

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Holocene variability of East Asian summer monsoon as viewed from the speleothem δ18O records in central China

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2021.116758 ◽

2021 ◽

Vol 558 ◽

pp. 116758

Author(s):

Yanjun Cai ◽

Xing Cheng ◽

Le Ma ◽

Ruixue Mao ◽

Sebastian F.M. Breitenbach ◽

...

Keyword(s):

Summer Monsoon ◽

East Asian Summer Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Central China ◽

Asian Summer

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Nonlinear, Intraseasonal Phases of the East Asian Summer Monsoon: Extraction and Analysis Using Self-Organizing Maps

Journal of Climate ◽

10.1175/jcli-d-11-00512.1 ◽

2012 ◽

Vol 25 (20) ◽

pp. 6975-6988 ◽

Cited By ~ 40

Author(s):

Jung-Eun Chu ◽

Saji N. Hameed ◽

Kyung-Ja Ha

Keyword(s):

Time Scales ◽

Summer Monsoon ◽

East Asian Summer Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Self Organizing Maps ◽

Dry Spell ◽

Asian Summer ◽

Upper Level ◽

Self Organizing

Abstract The hypothesis that regional characteristics of the East Asian summer monsoon (EASM) result from the presence of nonlinear coupled features that modulate the seasonal circulation and rainfall at the intraseasonal time scale is advanced in this study. To examine this hypothesis, the authors undertake the analysis of daily EASM variability using a nonlinear multivariate data classifying algorithm known as self-organizing mapping (SOM). On the basis of various SOM node analyses, four major intraseasonal phases of the EASM are identified. The first node describes a circulation state corresponding to weak tropical and subtropical pressure systems, strong upper-level jets, weakened monsoonal winds, and cyclonic upper-level vorticity. This mode, related to large rainfall anomalies in southeast China and southern Japan, is identified as the mei-yu–baiu phase. The second node represents a distinct circulation state corresponding to a strengthened subtropical high, monsoonal winds, and anticyclonic upper-level vorticity in southeast Korea, which is identified as the changma phase. The third node is related to copious rain over Korea following changma, which we name the postchangma phase. The fourth node is situated diagonally opposite the changma mode. Because Korea experiences a dry spell associated with this SOM node, it is referred to as the dry-spell phase. The authors also demonstrate that a strong modulation of the changma and dry-spell phases on interannual time scales occurs during El Niño and La Niña years. Results imply that the key to predictability of the EASM on interannual time scales may lie with analysis and exploitation of its nonlinear characteristics.

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The Variability of the Indian–East Asian Summer Monsoon Interface in Relation to the Spring Seesaw Mode between the Indian Ocean and the Central-Western Pacific

Journal of Climate ◽

10.1175/jcli-d-15-0839.1 ◽

2016 ◽

Vol 29 (13) ◽

pp. 5027-5040 ◽

Cited By ~ 7

Author(s):

Jie Cao ◽

Shu Gui ◽

Qin Su ◽

Yali Yang

Keyword(s):

Indian Ocean ◽

Summer Monsoon ◽

East Asian Summer Monsoon ◽

General Circulation ◽

Asian Summer Monsoon ◽

East Asian ◽

Western Pacific ◽

Observational Analysis ◽

Westerly Winds ◽

Asian Summer

Abstract The interannual zonal movement of the interface between the Indian summer monsoon and the East Asian summer monsoon (IIE), associated with the spring sea surface temperature (SST) seesaw mode (SSTSM) over the tropical Indian Ocean (TIO) and the tropical central-western Pacific (TCWP), is studied for the period 1979–2008. The observational analysis is based on Twentieth Century Reanalysis data (version 2) of atmospheric circulations, Extended Reconstructed SST data (version 3), and the Climate Prediction Center Merged Analysis of Precipitation. The results indicate that the IIE’s zonal movement is significantly and persistently correlated with the TIO–TCWP SSTSM, from spring to summer. The results of two case studies resemble those obtained by regression analysis. Experiments using an atmospheric general circulation model (ECHAM6) substantiate the key physical processes revealed in the observational analysis. When warmer (colder) SSTs appear in the TIO and colder (warmer) SSTs occur in the TCWP, the positive (negative) SSTSM forces anomalous easterly (westerly) winds over the Bay of Bengal (BOB), South China Sea (SCS), and western North Pacific (WNP). The anomalous easterly (westerly) winds further result in a weakened (strengthened) southwest summer monsoon over the BOB and a strengthened (weakened) southeast summer monsoon over the SCS and WNP. This causes the IIE to shift farther eastward (westward) than normal.

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