scholarly journals Reexamining the Mechanisms of East Asian Summer Monsoon Changes in Response to Non–East Asian Anthropogenic Aerosol Forcing

2020 ◽  
Vol 33 (8) ◽  
pp. 2929-2944 ◽  
Author(s):  
Zhili Wang ◽  
Junyu Mu ◽  
Meilin Yang ◽  
Xiaochao Yu
Keyword(s):  
East Asia ◽  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Eastern China ◽  
Fast Response ◽  
Anthropogenic Aerosol ◽  
Aerosol Forcing ◽  
Asian Summer

AbstractThis study examines the mechanisms by which the East Asian summer monsoon (EASM) changes in response to non–East Asian (NEA) anthropogenic aerosol forcing by distinguishing the fast direct atmospheric response and slow ocean-mediated response to forcing using a global aerosol–climate coupled model. The results show that NEA aerosol forcing significantly exacerbates the weakening of the EASM due to local aerosol forcing. The fast response is dominant in the weakening of the EASM and an anomalous precipitation pattern over eastern China resembling the “southern flood and northern drought” pattern in the total response to NEA aerosol forcing. Changes in upper-tropospheric temperature caused by the fast response play a major role in the impact of NEA aerosol forcing on the EASM. Anomalous cooling occurs during summer in the upper troposphere (at ~40°N) over East Asia caused by the fast response. This is due to the combined effects of strong eastward cold advection in the Northern Hemisphere midlatitudes caused by increased aerosol loading in Europe and the resulting change in local meridional heat transport in East Asia. Subsequently, the zonal wind speed changes on either side of the anomalous cooling, and the East Asian subtropical jet shifts equatorward, thereby weakening the EASM. The changes in atmospheric temperature and the local Hadley cell caused by the slow response to NEA aerosol forcing are conducive to strengthening the southwesterly winds over eastern China. Our study suggests the importance of NEA aerosol forcing in driving changes in the EASM on a fast time scale.

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.

scholarly journals Changing character of rainfall in eastern China, 1951–2007

2018 ◽  
Vol 115 (9) ◽  
pp. 2016-2021 ◽  
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.

scholarly journals Projections of East Asian summer monsoon change at global warming of 1.5 and 2 °C

2018 ◽  
Vol 9 (2) ◽  
pp. 427-439 ◽  
Author(s):  
Jiawei Liu ◽  
Haiming Xu ◽  
Jiechun Deng
Keyword(s):  
East Asia ◽  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Precipitation Change ◽  
High Latitudes ◽  
Multimodel Ensemble ◽  
Epr Method ◽  
Asian Summer

Abstract. Much research is needed regarding the two long-term warming targets of the 2015 Paris Agreement, i.e., 1.5 and 2 ∘C above pre-industrial levels, especially from a regional perspective. The East Asian summer monsoon (EASM) intensity change and associated precipitation change under both warming targets are explored in this study. The multimodel ensemble mean projections by 19 CMIP5 models show small increases in EASM intensity and general increases in summer precipitation at 1.5 and 2 ∘C warming, but with large multimodel standard deviations. Thus, a novel multimodel ensemble pattern regression (EPR) method is applied to give more reliable projections based on the concept of emergent constraints, which is effective at tightening the range of multimodel diversity and harmonize the changes of different variables over the EASM region. Future changes projected by using the EPR method suggest decreased precipitation over the Meiyu belt and increased precipitation over the high latitudes of East Asia and Central China, together with a considerable weakening of EASM intensity. Furthermore, reduced precipitation appears over 30–40∘ N of East Asia in June and over the Meiyu belt in July, with enhanced precipitation at their north and south sides. These changes in early summer are attributed to a southeastward retreat of the western North Pacific subtropical high (WNPSH) and a southward shift of the East Asian subtropical jet (EASJ), which weaken the moisture transport via southerly wind at low levels and alter vertical motions over the EASM region. In August, precipitation would increase over the high latitudes of East Asia with more moisture from the wetter area over the ocean in the east and decrease over Japan with westward extension of WNPSH. These monthly precipitation changes would finally contribute to a tripolar pattern of EASM precipitation change at 1.5 and 2 ∘C warming. Corrected EASM intensity exhibits a slight difference between 1.5 and 2 ∘C, but a pronounced moisture increase during extra 0.5 ∘C leads to enhanced EASM precipitation over large areas in East Asia at 2 ∘C warming.

scholarly journals Impacts of Tibetan Plateau Snow Cover on the Interannual Variability of the East Asian Summer Monsoon

2016 ◽  
Vol 29 (23) ◽  
pp. 8495-8514 ◽  
Author(s):  
Zhixiang Xiao ◽  
Anmin Duan
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Eastern China ◽  
Snow Albedo ◽  
Winter Snow ◽  
Asian Summer

Abstract The relationship between Tibetan Plateau (TP) snow cover and the East Asian summer monsoon (EASM) has long been discussed, but the underlying mechanism remains controversial. In this paper, the snow–albedo and snow–hydrology feedbacks over the TP are investigated based on multiple sources of snow data for the period 1979–2011. The results indicate that winter snow cover plays an important role in cooling local air temperature through the snow–albedo effect; the TP surface net solar radiation in years with above-normal snow cover is approximately 18 W m−2 less than that in below-normal snow cover years. However, data analysis demonstrates that persistent effects of winter snow cover are limited to the period from winter to spring over most parts of the central and eastern TP. Therefore, the preceding snow cover over the central and eastern TP exerts little influence over either the in situ summer atmospheric heat source or the EASM, because of its limited persistence. In contrast, the effects of winter or spring snow cover anomalies over the western TP and the Himalayas can last until summer, and these anomalies further influence the EASM by modulating moisture transport to eastern China and favoring eastward-propagating synoptic disturbances that are generated over the TP. Generally, above-normal snow cover over the western TP and the Himalayas facilitates abundant summer precipitation between the Yangtze and Yellow River basins, which is confirmed by results from a regional Weather Research and Forecasting model simulation.

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