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

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.

2015 ◽  
Vol 28 (22) ◽  
pp. 9013-9028 ◽  
Author(s):  
Xiao Luo ◽  
Yaocun Zhang

Abstract This study investigates the linkage between East Asian winter monsoon (EAWM) variability and upper-level jets, with particular focus on the East Asian polar front jet (PJ) and its concurrent variation with the subtropical jet located to the south of the Tibetan Plateau (TSJ). The winter upper-level zonal wind variations over the Asian landmass (70°–120°E) are dominated by two principal modes (i.e., meridional displacement of the PJ and out-of-phase variation in the intensity of the TSJ and PJ) and they are closely linked to the EAWM northern mode and southern mode, respectively. Southward shifting of the PJ concurs with northwestward displacement of the Siberian high (SH), an enhanced northern East Asian trough, leading to cold winter in northern East Asia. Meanwhile the simultaneous TSJ intensification and PJ weakening is linked to an amplified SH, a southward shift of the Aleutian low (AL), a strengthened southern East Asian trough, and a wavelike anomaly pattern extending from western Barents Sea downstream to East Asia at the 500-hPa level. Equatorward shift of the PJ is associated with La Niña conditions in the tropics and sea ice anomalies over the Arctic. An intensified TSJ and weakened PJ are preceded by autumn warming over the central and eastern Pacific Ocean and are linked to circulation anomalies induced by the extensions of stationary Rossby waves, as well as synoptic-scale transient eddy activity anomalies. Therefore, a combination of external forcing and internal atmospheric dynamics plays a role in driving the variations of two leading EOFs, and there is potential for seasonal forecasting of both modes.


2018 ◽  
Author(s):  
Zhixiang Wang ◽  
Yongjin Shen ◽  
Zhibin Pang

Abstract. The Tibetan Plateau uplift and its linkages with the evolution of the Asian climate during the Cenozoic are a research focus for numerous geologists. Here, a comprehensive review of tectonic activities across the Tibet shows that the development of the Tibetan Plateau has undergone mainly three stages of the uplift: the near-modern elevation of the central Tibet and significant uplift of the northern margins (~ 55–35 Ma), the further uplift of the plateau margins (30–20 Ma), and a rapid uplift of the plateau margins again (15–8 Ma). The first uplift of the plateau during ~ 55–35 Ma forced the long-term westward retreat of the Paratethys Sea. The high elevation of the central Tibet and/or the Himalayan would enhance rock weathering and erosion contributing to lowering of atmospheric CO2 content, resulting in global cooling. The global cooling, sea retreat coupled with the topographic barrier effect of the Tibetan Plateau could have caused the initial aridification in central Asia during the Eocene time. The second uplift of the northern Tibet could have resulted in the onset of the East Asian winter monsoon as well as intensive desertification of inland Asia, whereas the central-eastern in China became wet. The further strengthening of the East Asian winter monsoon and the inland Asian aridification during 15–8 Ma was probably associated with the Tibetan Plateau uplift and global cooling. Therefore, the uplift of the Tibetan Plateau plays a very important role in the Asian aridification.


2021 ◽  
pp. 118213
Author(s):  
L.I. Yanjun ◽  
A.N. Xingqin ◽  
Z.H.A.N.G. Peiqun ◽  
Y.A.N.G. Jianling ◽  
W.A.N.G. Chao ◽  
...  

2021 ◽  
pp. 1-14
Author(s):  
Qin Li ◽  
Haibin Wu ◽  
Jun Cheng ◽  
Shuya Zhu ◽  
Chunxia Zhang ◽  
...  

Abstract The East Asian winter monsoon (EAWM) is one of the most dynamic components of the global climate system. Although poorly understood, knowledge of long-term spatial differences in EAWM variability during the glacial–interglacial cycles is important for understanding the dynamic processes of the EAWM. We reconstructed the spatiotemporal characteristics of the EAWM since the last glacial maximum (LGM) using a comparison of proxy records and long-term transient simulations. A loess grain-size record from northern China (a sensitive EAWM proxy) and the sea surface temperature gradient of an EAWM index in sediments of the southern South China Sea were compared. The data–model comparison indicates pronounced spatial differences in EAWM evolution, with a weakened EAWM since the LGM in northern China but a strengthened EAWM from the LGM to the early Holocene, followed by a weakening trend, in southern China. The model results suggest that variations in the EAWM in northern China were driven mainly by changes in atmospheric carbon dioxide (CO2) concentration and Northern Hemisphere ice sheets, whereas orbital insolation and ice sheets were important drivers in southern China. We propose that the relative importance of insolation, ice sheets, and atmospheric CO2 for EAWM evolution varied spatially within East Asia.


The Holocene ◽  
2021 ◽  
pp. 095968362110190
Author(s):  
Tsai-Wen Lin ◽  
Stefanie Kaboth-Bahr ◽  
Kweku Afrifa Yamoah ◽  
André Bahr ◽  
George Burr ◽  
...  

The East Asian Winter Monsoon (EAWM) is a fundamental part of the global monsoon system that affects nearly one-quarter of the world’s population. Robust paleoclimate reconstructions in East Asia are complicated by multiple sources of precipitation. These sources, such as the EAWM and typhoons, need to be disentangled in order to understand the dominant source of precipitation influencing the past and current climate. Taiwan, situated within the subtropical East Asian monsoon system, provides a unique opportunity to study monsoon and typhoon variability through time. Here we combine sediment trap data with down-core records from Cueifong Lake in northeastern Taiwan to reconstruct monsoonal rainfall fluctuations over the past 3000 years. The monthly collected grain-size data indicate that a decrease in sediment grain size reflects the strength of the EAWM. End member modelling analysis (EMMA) on sediment core and trap data reveals two dominant grain-size end-members (EMs), with the coarse EM 2 representing a robust indicator of EAWM strength. The downcore variations of EM 2 show a gradual decrease over the past 3000 years indicating a gradual strengthening of the EAWM, in agreement with other published EAWM records. This enhanced late-Holocene EAWM can be linked to the expansion of sea-ice cover in the western Arctic Ocean caused by decreased summer insolation.


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