scholarly journals Recent Intensification of the Western Pacific Subtropical High Associated with the East Asian Summer Monsoon

2015 ◽  
Vol 28 (7) ◽  
pp. 2873-2883 ◽  
Author(s):  
Shinji Matsumura ◽  
Shiori Sugimoto ◽  
Tomonori Sato
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Western Pacific Subtropical High ◽  
Western Pacific ◽  
Subtropical High ◽  
The Past ◽  
The North ◽  
Asian Summer

Abstract The summer western Pacific subtropical high (WPSH) has intensified during the past three decades. However, the underlying mechanism is not yet well understood. Here, it is shown that baiu rainband activity in midsummer, which is part of the East Asian summer monsoon, plays an important role in recent intensification in the WPSH along the baiu rainband. In contrast with the WPSH, the summer Okhotsk high, which is located to the north of the baiu rainband, has weakened during the past three decades. The north–south contrasting changes between the two highs reflect a response to northward-moved and enhanced baiu heating, which intensifies the upper-tropospheric ridge, resulting in the baroclinic intensification of the WPSH. Regional climate model experiments also support the observational analysis. Therefore, baiu convective activity in midsummer can act as a major driver for the WPSH intensification. The results here suggest that the mechanism intensifying the summer North Pacific subtropical high clearly differs between the western and eastern Pacific.

scholarly journals 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

2016 ◽  
Vol 29 (13) ◽  
pp. 5027-5040 ◽  
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.

scholarly journals Assessing Future Changes in the East Asian Summer Monsoon Using CMIP5 Coupled Models

2013 ◽  
Vol 26 (19) ◽  
pp. 7662-7675 ◽  
Author(s):  
Kyong-Hwan Seo ◽  
Jung Ok ◽  
Jun-Hyeok Son ◽  
Dong-Hyun Cha
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Moisture Flux ◽  
Moisture Convergence ◽  
Cmip5 Models ◽  
Moisture Flux Convergence ◽  
The North ◽  
Asian Summer

Abstract Future changes in the East Asian summer monsoon (EASM) are estimated from historical and Representative Concentration Pathway 6.0 (RCP6) experiments of the fifth phase of the Coupled Model Intercomparison Project (CMIP5). The historical runs show that, like the CMIP3 models, the CMIP5 models produce slightly smaller precipitation. A moisture budget analysis illustrates that this precipitation deficit is due to an underestimation in evaporation and ensuing moisture flux convergence. Of the two components of the moisture flux convergence (i.e., moisture convergence and horizontal moist advection), moisture convergence associated with mass convergence is underestimated to a greater degree. Precipitation is anticipated to increase by 10%–15% toward the end of the twenty-first century over the major monsoonal front region. A statistically significant increase is predicted to occur mostly over the Baiu region and to the north and northeast of the Korean Peninsula. This increase is attributed to an increase in evaporation and moist flux convergence (with enhanced moisture convergence contributing the most) induced by the northwestward strengthening of the North Pacific subtropical high (NPSH), a characteristic feature of the future EASM that occurred in CMIP5 simulations. Along the northern and northwestern flank of the strengthened NPSH, intensified southerly or southwesterly winds lead to the increase in moist convergence, enhancing precipitation over these areas. However, future precipitation over the East China Sea is projected to decrease. In the EASM domain, a local mechanism prevails, with increased moisture and moisture convergence leading to a greater increase in moist static energy in the lower troposphere than in the upper troposphere, reducing tropospheric stability.

Decadal- to Centennial-Scale East Asian Summer Monsoon Variability Over the Past Millennium: An Oceanic Perspective

2018 ◽  
Vol 45 (15) ◽  
pp. 7711-7718 ◽  
Author(s):  
Richard Ching Wa Cheung ◽  
Moriaki Yasuhara ◽  
Briony Mamo ◽  
Kota Katsuki ◽  
Koji Seto ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
The Past ◽  
Monsoon Variability ◽  
Asian Summer ◽  
Past Millennium

scholarly journals Climatic Effects of China Large-Scale Urbanization on East Asian Summer Monsoon under Different Phases of Pacific Decadal Oscillation

Atmosphere ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 90
Author(s):  
Yongxiao Liang ◽  
Pengfeng Xiao
Keyword(s):  
Summer Monsoon ◽  
Pacific Decadal Oscillation ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Eastern China ◽  
Vertical Motion ◽  
Positive Phase ◽  
The North ◽  
Asian Summer

The effects of urbanization over eastern China on the East Asian summer monsoon (EASM) under different sea surface temperature background are compared using a Community Atmosphere Model (CAM5.1). Experiments of urbanization investigated by comparing two climate simulations with and without urban land cover under both positive and negative phases of Pacific Decadal Oscillation (PDO) show the spatial distribution of precipitation with ‘southern flood and northern drought’ and weakening status of EASM. The climate effect of urbanization in eastern China is significantly different from north to south. Anomalous vertical ascending motion due to the role of urbanization in the south of 30° N have induced an increase in convective available potential energy (CAPE) and precipitation increase over southern China. At the same time, the downward vertical motion occurs in the north of 30° N which cause warming over northern China. Due to the anti-cyclonic anomalies in the upper and lower layers of the north, the monsoon circulation is weakened which can reduce the precipitation. However, urbanization impact under various phases of PDO show different effect. In the 1956–1970 urbanization experiments of negative PDO phase, the downward vertical motion and anti-cyclonic anomalies in the north of 30° N are also weaker than that of positive phase of PDO in 1982–1996. In terms of this situation, the urbanization experiments of negative phase of PDO reveal that the range of the warming area over the north of 40° N is small, and the warming intensity is weak, but the precipitation change is more obvious compared with the background of positive phase of PDO.

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