Distinct effects of anthropogenic aerosols on the East Asian summer monsoon between multidecadal strong and weak monsoon stages

Xie, Xiaoning; Wang, Hongli; Liu, Xiaodong; Li, Jiandong; Wang, Zhaosheng; Liu, Yangang

doi:10.1002/2015jd024228

Cited by 39 publications

(43 citation statements)

References 56 publications

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“…In contrast, the cloud droplet effective radius in PD is markedly decreased by −1.39 µm, compared to PI (10.01 µm). The changes in these cloud properties are consistent with the notion that anthropogenic aerosol activation forms more cloud droplets, and reduces the conversion efficiency of cloud droplets to raindrops, which results in smaller cloud droplets and an increase in the liquid water path [13,18,27]. The amount of cloud, including low, mid-level, high, and total cloud cover, induced by aerosols shows an insignificant change from the mean values over East Asia for PD−PI in Table 1.…”

Section: Aerosol Effects On Cloud Properties and Radiative Forcingsupporting

confidence: 81%

“…First, the larger AOD over East Asia can cool the surface, stabilize the boundary layer, suppress the convective motion and decease the upward vertical velocity (Table 1) [13], which can effectively suppress the formation of clouds. Second, the larger AOD over East Asia can decrease the surface temperature, increase the sea level pressure over East Asia, and cause weaker changes to the EASM circulation [18], which can decrease the water vapor flux from the ocean ( Table 1). The decrease in water vapor flux can significantly suppress the formation of clouds over East Asia.…”

Section: Aerosol Effects On Cloud Properties and Radiative Forcingmentioning

confidence: 99%

“…Hence, the averaged meridional wind at 850 hPa in East Asia in summer is adopted to measure the large-scale intensity of the EASM [18]. Figure 5a shows the difference in the summer 850 hPa wind field between the PD and PI experiments (PD−PI).…”

Section: Aerosol Effects On East Asian Climatementioning

confidence: 99%

“…Other simulation studies have confirmed the notion of a weakened EASM circulation and reduced precipitation over eastern China in response to an increased amount of anthropogenic aerosols over East Asia, using the CAM5 model [14], the Coupled Model Intercomparison Project Phase 5 (CMIP5) models with prescribed sea surface temperature [15], and an online coupled regional climate-chemistry model [16]. Other studies have emphasized that the effects of aerosols on the EASM and the associated summer precipitation differ between strong and weak EASM years [17], and between strong and weak EASM stages [18].…”

Section: Introductionmentioning

confidence: 99%

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Effects of Aerosols on Radiative Forcing and Climate Over East Asia With Different SO2 Emissions

Xie

Liu

Wang³

et al. 2016

Atmosphere

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Abstract:It is known that aerosol and precursor gas emissions over East Asia may be underestimated by 50% due to the absence of data on regional rural and township industries. As the most important element of anthropogenic emissions, sulphur dioxide (SO 2 ) can form sulfate aerosols through several chemical processes, thus affecting the regional and global climate. In this study, we use the Community Atmospheric Model 5.1 (CAM5.1) to investigate the effects of anthropogenic aerosols on radiative forcing and the climate over East Asia, taking into consideration various SO 2 emission levels, including double the amount of SO 2 emissions over East Asia. Numerical experiments are performed using high-resolution CAM5.1 with pre-industrial (PI) and present day (PD) aerosol emission levels, and with PD aerosol emission levels with double SO 2 emissions over East Asia (PD2SO2). The simulated aerosol optical depth and surface sulfate concentrations over East Asia are significantly increased in PD2SO2, which is in better agreement with the observational results. The simulation results show extensive aerosol direct and indirect radiative forcing for PD−PI (the difference between PI and PD), which significantly weakens the large-scale intensity of the East Asian summer monsoon (EASM) and reduces the summer precipitation. Compared to PD, the aerosol direct radiative forcing is significantly increased in PD2SO2, whereas the aerosol indirect radiative forcing is markedly decreased due to the inhibition of cloud formation, especially over North China. The increase in aerosol direct radiative forcing and decrease in aerosol indirect radiative forcing result in insignificant changes in the total amount of aerosol radiative forcing. These results also show that the large-scale intensity of the EASM and the associated summer precipitation are insensitive to the doubling of current SO 2 emissions.

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Section: Aerosol Effects On Cloud Properties and Radiative Forcingsupporting

confidence: 81%

Section: Aerosol Effects On Cloud Properties and Radiative Forcingmentioning

confidence: 99%

Section: Aerosol Effects On East Asian Climatementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of Aerosols on Radiative Forcing and Climate Over East Asia With Different SO2 Emissions

Xie

Liu

Wang³

et al. 2016

Atmosphere

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“…To study the relationship between dust aerosols and the EASM, we used the average summer meridional wind at 850 hPa over eastern • N, 105-122.5 • E) as an EASM index, following Xie et al (2016). This index measures the intensity of the southerly wind to the east of the TP in the lower troposphere over East Asia.…”

Section: Relationship Between the Easm And Dust Loading Over The Tpmentioning

confidence: 99%

Direct radiative effects of dust aerosols emitted from the Tibetan Plateau on the East Asian summer monsoon – a regional climate model simulation

2017

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Abstract. While dust aerosols emitted from major Asian sources such as Taklimakan and Gobi deserts have been shown to have strong effect on Asian monsoon and climate, the role of dust emitted from Tibetan Plateau (TP) itself, where aerosols can directly interact with the TP "heat pump" because of their physical proximity both in location and elevation, has not been examined. This study uses the dustcoupled RegCM4.1 regional climate model (RCM) to simulate the spatiotemporal distribution of dust aerosols originating within the TP and their radiative effects on the East Asian summer monsoon (EASM) during both heavy and light dust years. Two 20-year simulations with and without the dust emission from TP showed that direct radiative cooling in the mid-troposphere induced by the TP locally produced dust aerosols resulted in an overall anticyclonic circulation anomaly in the low troposphere centered over the TP region. The northeasterly anomaly in the EASM region reduces its strength considerably. The simulations found a significant negative correlation between the TP column dust load produced by local emissions and the corresponding anomaly in the EASM index (r = −0.46). The locally generated TP dust can cause surface cooling far downstream in Bohai Gulf and the China-North Korea border area through stationary Rossby wave propagation. Although dust from within TP (mainly Qaidam Basin) is a relatively small portion of total Asian aerosols, its impacts on Asian monsoon and climate seems disproportionately large, likely owning to its higher elevation within TP itself.

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Aerosol effects on summer monsoon over Asia during 1980s and 1990s

et al. 2016

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The Community Earth System Model is used to study the aerosol climate effects during the 1980s and 1990s in which the anthropogenic SO2 emissions decreased in North America and Western Europe and increased in East and South Asia. From the 100 year simulations, aerosol forcing results in cooler (−0.13 K) and drier (−0.01 mm/day) atmosphere with less shortwave radiation flux at the surface (−0.37 W/m2). The clear‐sky shortwave radiation flux decreased over East Asia (−0.81 W/m2) and South Asia (−1.09 W/m2), but increased over Western Europe (+1.16 W/m2) and North America (+0.39 W/m2), consistent with aerosol loading changes. While changes in spatial distributions of all‐sky shortwave radiation and surface temperature are closely related to cloud changes, the changes in wind and precipitation do not correspond to aerosol loading changes, indicating the complexity of aerosol‐cloud circulation interactions. The East and South Asia monsoons were generally weakened due mainly to southward shift of the 200 hPa East Asia Jet (EAJ) and decrease in 850 hPa winds; annual precipitation decreased by 2% in South Asia but increased by 2% in Yangtze‐Huai River Valley over East Asia. The uncertainties associated with aerosol climate effects are addressed within the context of model variability and the global warming effect. For the latter, while the aerosol effects decrease the greenhouse warming on the global mean, the regional responses are different. Nevertheless, the characteristics of aerosol climate effects, including the southward 200 hPa EAJ and weakened South Asia monsoon, still persist when the climate becomes warmer, although the strength and the geographical distribution are slightly modulated.

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Distinct effects of anthropogenic aerosols on the East Asian summer monsoon between multidecadal strong and weak monsoon stages

Cited by 39 publications

References 56 publications

Effects of Aerosols on Radiative Forcing and Climate Over East Asia With Different SO2 Emissions

Effects of Aerosols on Radiative Forcing and Climate Over East Asia With Different SO2 Emissions

Direct radiative effects of dust aerosols emitted from the Tibetan Plateau on the East Asian summer monsoon – a regional climate model simulation

Aerosol effects on summer monsoon over Asia during 1980s and 1990s

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