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

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
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.

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 Revisiting the Physical Mechanisms of East Asian Summer Monsoon Precipitation Changes During the Mid-Holocene: A Data–model Comparison

2021 ◽  
Author(s):  
Yong Sun ◽  
Haibin Wu ◽  
Gilles Ramstein ◽  
Bo Liu ◽  
Yan Zhao ◽  
...  
Keyword(s):  
East Asia ◽  
Summer Monsoon ◽  
Data Model ◽  
East Asian Summer Monsoon ◽  
Model Comparison ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Asian Summer ◽  
Dynamic Components ◽  
Precipitation Changes

Abstract The mid-Holocene (MH; 6 ka) is one of the benchmark periods for the Paleoclimate Modeling Intercomparison Project (PMIP) and provides a unique opportunity to study monsoon dynamics and orbital forcing (i.e., mostly precession) that differ significantly from the present day. We conducted a data–model comparison along with a dynamic analysis to investigate monsoonal (i.e., East Asian summer monsoon; EASM) precipitation changes over East Asia during the MH. We used the three phases of the PMIP simulations for the MH, and quantitatively compared the model results with pollen-based climate records. The data–model comparison shows an overall increase in precipitation, except for a local decrease in EASM precipitation during the MH. Decomposition of the moisture budget into thermodynamic, dynamic components and co-variations in both allowed us to assess the relative role of thermodynamic and dynamic components in controlling EASM precipitation during the MH, and to investigate the precipitation changes obtained from pollen records in terms of physical processes. We show that the dynamic effect, rather than the thermodynamic effect, is the dominant control in increased EASM precipitation during the MH in both the proxy records and models. The dynamic increase in precipitation results mainly from the enhancement of horizontal monsoonal moisture transport that is caused by intensified stationary eddy horizontal circulation over East Asia. In addition, a cloud cooling effect reduced the thermodynamic contribution to the increase in EASM precipitation during the MH.

A New Upper-Level Circulation Index for the East Asian Summer Monsoon Variability

2015 ◽  
Vol 28 (24) ◽  
pp. 9977-9996 ◽  
Author(s):  
Guijie Zhao ◽  
Gang Huang ◽  
Renguang Wu ◽  
Weichen Tao ◽  
Hainan Gong ◽  
...  
Keyword(s):  
East Asia ◽  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Late Summer ◽  
Good Choice ◽  
Circulation Index ◽  
Asian Summer

Abstract The East Asian summer monsoon (EASM) and its variability involve circulation systems in both the tropics and midlatitudes as well as in both the lower and upper troposphere. Considering this fact, a new EASM index (NEWI) is proposed based on 200-hPa zonal wind, which takes into account wind anomalies in the southern (about 5°N), middle (about 20°N), and northern areas (about 35°N) of East Asia. The NEWI can capture the interannual EASM-related climate anomalies and the interdecadal variability well. Compared to previous indices, the NEWI shows a better performance in describing precipitation and air temperature variations over East Asia. It can also show distinct climate anomalous features in early and late summer. The NEWI is tightly associated with the East Asian–Pacific or the Pacific–Japan teleconnection, suggesting a possible role of internal dynamics in the EASM variability. Meanwhile, the NEWI is significantly linked to El Niño–Southern Oscillation and tropical Indian Ocean sea surface temperature anomalies. Furthermore, the NEWI is highly predictable in the ENSEMBLES models, indicating its advantage for operational prediction of the EASM. The physical mechanism of the EASM variability as represented by the NEWI is also explicit. Both warm advection anomalies of temperature by anomalous westerly winds and the advection of anomalous positive relative vorticity by northerly basic winds cause anomalous ascending motion over the mei-yu–changma–baiu rainfall area, and vice versa over the South China Sea area. Hence, this NEWI would be a good choice to study, monitor, and predict the EASM.

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

2018 ◽  
Author(s):  
Jiawei Liu ◽  
Haiming Xu ◽  
Jiechun Deng
Keyword(s):  
East Asia ◽  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
High Latitudes ◽  
Multimodel Ensemble ◽  
Epr Method ◽  
Asian Summer ◽  
Precipitation Changes

Abstract. Much research is needed regarding two long-term warming targets of the 2015 Paris Agreement, i.e., 1.5 °C and 2 °C above pre-industrial levels, especially from a regional perspective. The East Asian summer monsoon (EASM) intensity and associated precipitation changes under both warming targets are explored in this study. 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 to tighten 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, suppressed precipitation would appear 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 western North Pacific high (WNPSH) and a southward shift of East Asian subtropical jet (EASJ), which weaken the moisture transport via southerly wind at low level 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 °C 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 Distinct Modes of the East Asian Summer Monsoon*

2008 ◽  
Vol 21 (5) ◽  
pp. 1122-1138 ◽  
Author(s):  
Bingyi Wu ◽  
Renhe Zhang ◽  
Yihui Ding ◽  
Rosanne D’Arrigo
Keyword(s):  
Heat Source ◽  
Convective Heat ◽  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Northwestern Pacific ◽  
Okhotsk Sea ◽  
Southeastern China ◽  
Asian Summer

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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