Asian Aerosol Research Articles

Increased Asian Sulfate Aerosol Emissions Remarkably Enhance Sahel Summer Precipitation

AbstractObservational evidence shows that Sahel summer precipitation has experienced a considerable increase since the 1980s, coinciding with significant diverging trends of increased sulfate emissions in Asia and decreased emissions in Europe (dipole pattern of aerosols between Asia and Europe). The decrease in European sulfate aerosols has substantial effects on the Sahel summer precipitation increase, but the corresponding effect of increased Asian sulfate is unknown. Multi‐model simulations in the Precipitation Driver and Response Model Intercomparison Project (PDRMIP) show, compared to decreased European aerosols, that increased Asian aerosols similarly enhance the Sahel summer precipitation but with different large‐scale atmospheric circulation changes. Further analysis of the Sixth Coupled Model Intercomparison Project (CMIP6) simulations under historical attribution and various emission scenarios reinforces the results about the climate impacts of anthropogenic aerosols and suggests that in future scenarios with strong international cooperation and rapid climate mitigations (SSP2‐45), the Sahel drought will be intensified likely due to the decline in Asian aerosol emissions. Our results suggest that Asian anthropogenic aerosols are likely a non‐negligible driver of the recent recovery in Sahel precipitation amounts.

Impact of Asian aerosols on the summer monsoon strongly modulated by regional precipitation biases

Abstract. Reliable attribution of Asian summer monsoon variations to aerosol forcing is critical to reducing uncertainties in future projections of regional water availability, which is of utmost importance for risk management and adaptation planning in this densely populated region. Yet, simulating the monsoon remains a challenge for climate models that suffer from long-standing biases, undermining their reliability in attributing anthropogenically forced changes. We analyze a suite of climate model experiments to identify a link between model biases and monsoon responses to Asian aerosols and associated physical mechanisms, including the role of large-scale circulation changes. The aerosol impact on monsoon precipitation and circulation is strongly influenced by a model's ability to simulate the spatio-temporal variability in the climatological monsoon winds, clouds, and precipitation across Asia, which modulates the magnitude and efficacy of aerosol–cloud–precipitation interactions, an important component of the total aerosol response. There is a strong interplay between South Asia and East Asia monsoon precipitation biases and their relative predominance in driving the overall monsoon response. We found a striking contrast between the early- and late-summer aerosol-driven changes ascribable to opposite signs and seasonal evolution of the biases in the two regions. A realistic simulation of the evolution of the large-scale atmospheric circulation is crucial to realize the full extent of the aerosol impact over Asia. These findings provide important implications for better understanding and constraining the diversity and inconsistencies of model responses to aerosol changes over Asia in historical simulations and future projections.

Long range transport of South and East Asian anthropogenic aerosols counteracting Arctic warming

The large-scale convection during the Asian summer monsoon plays an important role in the rapid transport of boundary layer aerosols into the Asian summer monsoon anticyclone. Here, using the state-of-the-art ECHAM6–HAMMOZ aerosol-chemistry-climate model, we show that these aerosols are further transported to the Arctic along isentropic surfaces by the Brewer-Dobson-Circulation (BDC) during the monsoon season. Our model simulations show that East and South Asian anthropogenic emissions contribute significantly to the aerosol transported to the Arctic, which causes a higher negative net aerosol radiative forcing at the surface (dimming) of −0.09 ± 0.02 Wm−2 and −0.07 ± 0.02 Wm−2, respectively. Over the Arctic, the East Asian anthropogenic aerosols that include large amounts of sulfate cause a seasonal mean net radiative forcing at the top of the atmosphere (TOA) of −0.003 ± 0.001Wm−2 and a surface cooling of −0.56 K while the black carbon dominated aerosol from South Asia shows a positive TOA forcing of +0.004 ± 0.001Wm−2 with an only minor surface cooling of −0.043 K. Overall, the long-range transport of South Asian aerosols results in a notably warming throughout the atmospheric column but minimal temperature response at the Arctic surface. Conversely, East Asian aerosols cool the troposphere and heat the lower stratosphere in the Arctic. The Asian aerosol thus plays an ambivalent role, with the East Asian sources in particular having the potential to counteract the rapid rise in Arctic temperatures and the associated melting of snow and ice.

A novel potential cause of extreme precipitation in the northwest China

The northwest China is a climate change-sensitive and ecologically vulnerable area. Under the backdrop of global warming, this region exhibits clear characteristics of warming and wetting. In recent years, the causes of climate change in the northwest China has become a widely-focused topic. Previous research has mainly attributed the increase in precipitation to changes in the westerly belt and enhanced local convective activity caused by global warming. South Asia, beside the Tibetan Plateau from the northwest China, is one of the regions with the fastest growth in global atmospheric pollutant emissions. This study utilizes reanalysis data such as ERA5 and MERRA-2. Statistical methods, including Theil-Sen Median trend analysis and Singular Value Decomposition analysis, are employed to analyze the spatiotemporal characteristics of South Asian aerosols, extreme precipitation in the northwest China, and the correlation between the two. The study reveals the existence of two key aerosol-precipitation response areas. Synthetic analysis of the meteorological elements of the response events in both regions is conducted to explore the possible physical mechanisms behind the correlation between South Asian aerosols and precipitation in the northwest China. The result of this study is to provide a new perspective on the causes of extreme precipitation in the arid region of northwest China.

Increased Asian aerosols drive a slowdown of Atlantic Meridional Overturning Circulation

Observational evidence and climate model experiments suggest a slowdown of the Atlantic Meridional Overturning Circulation (AMOC) since the mid-1990s. Increased greenhouse gases and the declined anthropogenic aerosols (AAs) over North America and Europe are believed to contribute to the AMOC slowdown. Asian AAs continue to increase but the associated impact has been unclear. Using ensembles of climate simulations, here we show that the radiative cooling resulting from increased Asian AAs drives an AMOC reduction. The increased AAs over Asia generate circumglobal stationary Rossby waves in the northern midlatitudes, which shift the westerly jet stream southward and weaken the subpolar North Atlantic westerlies. Consequently, reduced transport of cold air from North America hinders water mass transformation in the Labrador Sea and thus contributes to the AMOC slowdown. The link between increased Asian AAs and an AMOC slowdown is supported by different models with different configurations. Thus, reducing emissions of Asian AAs will not only lower local air pollution, but also help stabilize the AMOC.

Anthropogenic Aerosols Contribute to the Recent Decline in Precipitation Over the U.S. Southwest

AbstractThe winter‐spring precipitation over the Southwestern United States (SWUS) decreased since 1980. It is frequently attributed to Pacific internal decadal variability, but recent studies found anthropogenic aerosols (AA) can also induce a transition to a negative Pacific Decadal Variability (PDV) phase. We revisit the attribution of SWUS drying by quantifying the contributions of anthropogenically forced decadal Pacific Sea Surface Temperatures (SSTs). Applying a low‐frequency component analysis to observations, Community Earth System Model version 2 (CESM2) all‐forcings and single‐forcing large ensembles, we find up to 42% of the observed precipitation trend to be related to the AA‐induced negative PDV‐like pattern, which is driven by the emission shift from the Western to the Eastern Hemisphere. In CESM2, other radiative forcings counteract the influence of AA, but it remains unclear whether the model correctly simulates this balance. This implies that the near‐future trajectories of these forcings, in particular Asian aerosols, are important for projections of SWUS precipitation.

An emerging Asian aerosol dipole pattern reshapes the Asian summer monsoon and exacerbates northern hemisphere warming

Since the early 2010s, anthropogenic aerosols have started decreasing in East Asia (EA) while have continued to increase in South Asia (SA). Yet the climate impacts of this Asian aerosol dipole (AAD) pattern remain largely unknown. Using a state-of-the-art climate model, we demonstrate that the climate response is distinctly different between the SA aerosol increases and EA aerosol decreases. The SA aerosol increases lead to ~2.7 times stronger land summer precipitation change within the forced regions than the EA aerosol decreases. Contrastingly, the SA aerosol increases, within the tropical monsoon regime, produce weak and tropically confined responses, while the EA aerosol decreases yield a pronounced northern hemisphere warming aided by extratropical mean westerly and positive air-sea feedbacks over the western North Pacific. By scaling the observed instantaneous shortwave radiative forcing, we reveal that the recent AAD induces a pronounced northern hemisphere extratropical (beyond 30°N) warming (0.024 ± 0.010 °C decade−1), particularly over Europe (0.049 ± 0.009 °C decade−1). These findings highlight the importance of the pattern effect of forcings in driving global climate and have important implications for decadal prediction.

The solubility and deposition flux of East Asian aerosol metals in the East China Sea: The effects of aeolian transport processes

Aerosol dissolvable metals are considered to be readily bioaccessible so that their input would influence the growth and composition of marine phytoplankton and affect elemental cycling globally. However, it is highly challenging to measure or estimate reliable deposition fluxes of aerosol dissolvable metals in the ocean partially due to the impacts of complicated processes involved in pre- and post-deposition of aerosols. We have collected lithogenic dust from major Chinese deserts and size-fractionated aerosols from the East China Sea (ECS) to study the variations of their dissolvable metals by using three operationally defined leaching protocols (ultrapure water, buffer, and Berger leaches). We have systematically investigated the changes of the distribution patterns of the metals to evaluate the potential impacts of the transport processes on the flux estimates of different elements. In addition to the extremely high solubilities observed for anthropogenic type elements, we found variations for solubilities of lithogenic type elements (Ti, Al, Fe) increase with increasing sizes by the three leaching treatments. Without knowing the size specific information (mass and solubility), our observations indicate that the deposition fluxes of lithogenic type elements would be significantly overestimated. Compared with the solubility of the desert dust, we found that all solubilities for lithogenic type elements in the largest aerosols were significantly enhanced. For example, the Fe solubilities increased up to 68, 6, and 3 folds for ultrapure water, buffer, and Berger treatments, respectively. Attributed to the difference of the impacts of the transport processes in different regions, the extent of the enhancement would be region specific. Comparing some other recent laboratory studies, we argue that the solubilities obtained by buffer and Berger leaches are more realistic to represent aerosol solubility in the ocean than ultrapure water leach. It would be essential to carry out similar field studies in other regions as this study to obtain region specific parameters of dissolvable aerosol metals to achieve better global modeling estimates on the fluxes of dissolvable aerosol metals in the ocean.

Impacts of Anthropogenic Emissions over South Asia on East Asian Spring Climate: Two Possible Dynamical Pathways

Abstract Both South Asia and East Asia are the most polluted regions of the world. Unlike East Asia, the aerosol optical depth (AOD) over South Asia keeps increasing for all recent years, which calls for more attention. This study investigates the impacts of anthropogenic emissions over South Asia on the downstream regional climate during spring with the Community Earth System Model 2 (CESM2). The model results suggest that South Asian pollutants have significant impacts on East Asian spring climate, and the impacts could be even larger than locally emitted aerosols. Two possible dynamical pathways (i.e., the northern and the southern pathways) bridging South Asian aerosol forcing and East Asian climate are proposed, and both ways are associated with the black carbon (BC)-induced climate feedbacks surrounding the Tibetan Plateau (TP). The northern pathway is mainly due to the TP warming induced by the BC snow darkening effect (SDE), which significantly reduces the surface air temperature (SAT) over northern East Asia. BC-induced TP warming increases the meridional thermal gradient and accelerates the midlatitude jet stream, which favors the cold-air advection over northern East Asia. The southern pathway is associated with the BC “elevated heat pump” hypothesis, which mainly affects the precipitation in southern East Asia. BC from South Asia accumulates near the south slope of TP, inducing an abnormal ascending motion near the Bay of Bengal. A compensating anomalous sinking motion is then forced in South China, which suppresses the precipitation there. A primary observational analysis is also performed to verify both dynamical pathways. Significance Statement The intensified air pollution over South Asia and its impacts on local climate have been extensively investigated, but its impacts on the climate of remote regions have not been well recognized. Two possible dynamical pathways bridging South Asian air pollutants and East Asian spring climate are proposed, and the black carbon (BC)-induced climate feedbacks surrounding the Tibetan Plateau (TP) are emphasized for both pathways. The findings of this study favor the projection of East Asian future climate under the background of Third Pole/TP warming.

Dust emission and potential diffusion process in Mongolia

AbstractMongolian dust is an important part of Asian aerosols, which highly influences regional ecological balance and atmospheric environment cycling. Detailed and systematic research is essential for downwind countries of Mongolia to formulate appropriate strategies for dust disaster prevention. In this study, a size‐resolved dust emission scheme and a hybrid single‐particle Lagrangian integrated trajectory model were coupled to reproduce the Mongolian dust events. For the dust storm that occurred on March 14, 2021, the simulated dust source was mainly located in the Gobi Provinces and a narrow strip between the Altai and Khangai Mountains. The potential diffusion area of dust was approximately 8.59 × 106 km2. The long‐term simulation between 2001 and 2020 shows that Mongolian dust sources can be divided into three areas: southwest Mongolia, the Gobi Provinces, and the area between the Altai and Khangai Mountains. Dust emissions can reach 100.6 Tg year−1, affecting approximately 12.6 × 106 km2 of land in East Asia. The emission and transport characteristics of Mongolian dust vary according to the sources. Southwestern Mongolia has the most severe dust emissions and the Gobi Provinces have the strongest diffusion capacity. Southern Mongolia and northern China have always been the hotspots of Mongolian dust transportation and deposition and thus require more research attention. This study provides a comprehensive analysis of Mongolian dust and presents a potential diffusion map that can be used to formulate preventive measures.

Influence of Spatial Dipole Pattern in Asian Aerosol Changes on East Asian Summer Monsoon

Abstract Since China implemented the Air Pollution Prevention and Control Action Plan in 2013, the aerosol emissions in East Asia have been greatly reduced, while emissions in South Asia have continued to increase. This has led to a dipole pattern of aerosol emissions between South Asia and East Asia. Here, the East Asian summer monsoon (EASM) responses to the dipole changes in aerosol emissions during 2013–17 are investigated using the atmosphere model of Community Earth System Model version 2 (CESM2). We show that decreases in East Asian emissions alone lead to a positive aerosol effective radiative forcing (ERF) of 1.59 (±0.97) W m−2 over central-eastern China (25°–40°N, 105°–122.5°E), along with a 0.09 (±0.07)°C warming in summer during 2013–17. The warming intensified the land–sea thermal contrast and increased the rainfall by 0.32 (±0.16) mm day−1. When considering both the emission reductions in East Asia and increases in South Asia, the ERF is increased to 3.39 (±0.89) W m−2, along with an enhanced warming of 0.20 (±0.08)°C over central-eastern China, while the rainfall insignificant decreased by 0.07 (±0.16) mm day−1. It is due to the westward shift of the strengthened western Pacific subtropical high, linked to the increase in black carbon in South Asia. Based on multiple EASM indices, the reductions in aerosol emissions from East Asia alone increased the EASM strength by almost 5%. Considering the effect of the westward shift of WPSH, the dipole changes in emissions together increased the EASM by 5%–15% during 2013–17, revealing an important role of South Asian aerosols in changing the East Asian climate.

Application of DIAL/HSRL and CATCH algorithm-based methodologies for surface PM2.5 concentrations during the KORUS-AQ campaign

Particulate matter with an aerodynamic diameter of equal to or less than 2.5 μm (PM2.5) has been found to have a serious adverse effect on human health and the environment. While the importance of measuring PM2.5 has been demonstrated, doing so remotely remains challenging. In this study, methodologies for the assessment of aerosol PM2.5 and chemical composition based on a combination of regional and global models and active remote sensing were evaluated against surface observations from the KORUS-AQ campaign. The model outputs from the Community Multiscale Air Quality (CMAQ) and GEOS-Chem were used and were available at the KORUS-AQ campaign data archive. For remote sensing, aerosol extinction and derived aerosol types available from NASA Langley Airborne Differential Absorption Lidar (DIAL)/High Spectral Resolution Lidar (HSRL) flying onboard DC-8 aircraft were used. A revised version of the algorithm, which incorporates size-specific aerosol dry mass extinction efficiencies for sulfate, nitrate, and ammonia as well as organic matter, is also presented. The PM2.5 concentration estimates were compared with measurements taken at the ground stations. The estimated mean absolute error between the ground station measurements and the remote-sensing-based methodologies was significantly lower compared to the models. The data analysis has shown that uncertainties in relative humidity values, the presence of particles larger than 2.5 μm in diameter, and the abundance of black carbon and organic matter in Asian aerosol were unlikely to explain the differences between measured and predicted surface PM2.5. Local meteorology was found to play a key role influencing the spatiotemporal variability of aerosols and the most important factor determining the agreement between the estimated and ground site-measured PM2.5. The lowest mean absolute error was found for the May 1–16 period, when aerosols were well mixed within the mixing layer and homogeneous across the temporal (1 h) and spatial (8 km) scales used in this study. Under these conditions, the methodologies presented here could give reasonable estimates of PM2.5 concentration and derived chemical composition over South Korea when HSRL data are available.

Identifying spatio-temporal climatic characteristics and events of the South-Asian aerosol pollution transport to the Tibetan Plateau

South Asian aerosol pollutants can be transported to the Tibetan Plateau (TP) and affect the local atmospheric environment; however, few studies have produced statistical results for the long term. In this study, 41 years of pollution transport events from South Asia to the TP were screened based on Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) reanalysis data using objective methods, and the main pollution transport mechanisms were revealed. We used the empirical orthogonal functions (EOF) and the rotated empirical orthogonal functions (REOF) methods to obtain the spatiotemporal variation characteristics of the aerosol optical depth (AOD) over the TP and the large loading regions of AOD variation from 1980 to 2020 and combined them with the backward trajectory to screen for severe pollution events in the TP influenced by transport from South Asia. The three regions (eastern, central and western regions) with large AOD loading variations in the southern TP are shown by the REOF. Based on the objectively defined AOD indices for the three regions, 2058 days of strong pollution were identified, of which 1702 days (82.7%) were affected by pollution transport from South Asia. Of these 1702 days, the central region had the highest number of days at 661 (38.8%), followed by the western and eastern regions with 544 (32%) and 497 (29.2%) days, respectively. The results obtained from the transport events in the three regions suggest that South Asian pollutants can be transported across the Himalayas to the TP by valley winds, north-south valley passages, and cyclonic uplift. These findings deepen the understanding of the aerosol pollution of the TP affected by pollution transport from South Asia.

Spatial‐Temporal Variability and Sources of Lead (Pb) in the Indian Ocean and Asian Marginal Seas

AbstractSince North America and European countries phased out leaded gasoline, Asia has become the major contemporary lead (Pb) source to the marine environment, at first from leaded gasoline, but more recently from coal burning and other high‐temperature industrial activities (Flegal et al., 2013, https://doi.org/10.1080/10643389.2012.671738; Lee et al., 2014, https://doi.org/10.1016/j.epsl.2014.04.030). Pb in the Indian Ocean remains relatively under‐evaluated after ∼2000 and is further complicated by various oceanic processes (e.g., monsoons, boundary exchange with particulates). Here, we present three annually resolved coral skeletal Pb isotope and concentration records from the central and eastern Indian Ocean (Salomon Atoll, 1989–2009; Diego Garcia Atoll, 1999–2009; and Phuket Island, 1945–2010), and synthesize published coral/sedimentary records to reconstruct the spatial‐temporal variability of anthropogenic Pb around the region. Pb isotopes in all corals coherently fall along the mixing line between Asian aerosols and the natural crust. However, higher contributions of natural Pb are found in corals located in the coastal region than those in the open ocean, despite the greater contributions of anthropogenic Pb expected in coastal water near human emission sources. This geographical difference suggests that exchanges between dissolved Pb and natural particles at ocean boundaries significantly contribute to the Pb isotope compositions in regional seawater and are subsequently recorded in corals. The temporal variability of Pb concentrations in corals and sedimentary records signifies decreasing trends in Southeast Asia but increasing trends in South Asia. This study contributes new and timely Pb and Pb isotope data for the Indian Ocean and illustrates the importance of boundary exchange in marine Pb cycling.

Friendship Creates Intercontinental Cooperation in Aerosol Research

At the Asian Aerosol Conference 2022 a Commemorative Session took place to honor Prof. Dr. Dave Pui for fifty years of successful aerosol research, working together with students and post docs, mainly from Asia and aerosol scientist from all over the world and honor him for his friendship activities within the aerosol community. I know Dave 50 years. We collaborated for more than 40 years, supported by students, post docs, other colleagues and our families based on a deep, still going on friendship.

Aerosol Nutrients and Their Biological Influence on the Northwest Pacific Ocean (NWPO) and Its Marginal Seas.

Simple SummaryWith intensifying human activities in the past decades, East Asia has recorded increasingly severe air pollution and become the second largest aerosol source on earth. The large quantity of aerosol emissions is not only a major health threat to humans, but can also be transported for a long distance and deposited in downwind seas and oceans. The aerosol contains major ions, heavy metals, and organic matters that are important external nutrients in upper oceans and potentially influence marine microbes and biogeochemical cycles. Therefore, the role of atmospheric deposition to oceans has received growing attention in recent years. In this paper, the current state of knowledge on the atmospheric nutrients and the biological effect of East Asian aerosol deposition on the northwest Pacific Ocean are reviewed, which could help us better understand the comprehensive influence of East Asian aerosols on marine ecosystems, and give insights into future research directions, especially under the future scenarios of changing human activities and climate.Atmospheric deposition is recognized as a significant source of nutrients in the surface ocean. The East Asia region is among the largest sources of aerosol emissions in the world, due to its large industrial, agricultural, and energy production. Thus, East Asian aerosols contain a large proportion of anthropogenic particles that are characterized by small size, complex composition, and high nutrient dissolution, resulting in important influences on marine microbes and biogeochemical cycles in the downwind areas of the northwest Pacific Ocean (NWPO). By using remote sensing, modeling, and incubation experimental methods, enhanced primary production due to the East Asian aerosol input has been observed in the NWPO, with subsequent promotion and inhibition impacts on different phytoplankton taxa. Changes of bacterial activity and diversity also occur in response to aerosol input. The impact of East Asian aerosol loadings is closely related to the amount and composition of the aerosol deposition as well as the hydrological condition of the receiving seawater. Here, we review the current state of knowledge on the atmospheric nutrients and the effects of the East Asian aerosols on microbes in the NWPO region. Future research perspectives are also proposed.

Aerosols over East and South Asia: Type Identification, Optical Properties, and Implications for Radiative Forcing

Identification of aerosol types has long been a difficult problem over East and South Asia due to various limitations. In this study, we use 2-dimensional (2-D) and multi-dimensional Mahalanobis distance (MD) clustering algorithms to identify aerosol characteristics based on the data from the Aerosol Robotic Network from March 1998 to February 2018 over the South and East Asian region (10°N~50°N, 70°E~135°E). The single scattering albedo (SSA), absorption Angstrom exponent (AAE), extinction Angstrom exponent (EAE), real index of refraction (RRI), and imaginary index of refraction (IRI) are utilized for classification of aerosols. Sub-regions with similar background conditions over East and South Asia are identified by hierarchical clustering algorithm to illustrate distinctive meteorological states in different areas. The East and South Asian aerosols are found to have distinct regional and seasonal features relating to the meteorological conditions, land cover, and industrial infrastructure. It is found that the proportions of dust aerosol are the highest in spring at the SACOL site and in summer at the sites near the Northern Indo-Gangetic Plain area. In spring, biomass-burning aerosols are dominant over the central Indo-China Peninsula area. The aerosol characteristics at coastal sites are also analyzed and compared with previous results. The 2-D clustering method is useful when limited aerosol parameters are available, but the results are highly dependent on the sets of parameters used for identification. Comparatively, the MD method, which considers multiple aerosol parameters, could provide more comprehensive classification of aerosol types. It is estimated that only about 50% of the data samples that are identifiable by the MD method could be classified by the 2-D methods, and a lot of undetermined data samples could be mis-classified by the 2-D methods. The aerosol radiative forcing (ARF) and the aerosol radiative forcing efficiency (ARFE) of various aerosol types at the top and the bottom of the atmosphere (TOA and BOA) are determined based on the MD aerosol classification. The dust aerosols are found to have the largest ARF at the TOA (−36 W/m2), followed by the urban/industrial aerosols and biomass-burning aerosols. The ARFE of biomass-burning aerosols at the BOA (−165 W/m2/AOD550nm) is the strongest among those of the other aerosol types. The comparison of the results by MD and 2-D methods shows that the differences in ARF and ARFE are generally within 10%. Our results indicate the importance of aerosol type classification in accurately attributing the radiative contributions of different aerosol components.

Little Influence of Asian Anthropogenic Aerosols on Summer Temperature in Central East Asia Since 1960

AbstractRecent summer surface air temperature (SAT) variations over Central East Asia (CEA) have been influenced by greenhouse gas and aerosol forcing since 1960. But how CEA SAT responds to contrasting changes in Asian, and European and North American aerosol sources remains unclear. By analyzing observations and model simulations, here we show that aerosol‐forced summer SAT changes over CEA since 1960 come mostly from the effects of aerosols outside Asia, with relatively small influences from Asian aerosols. Unlike Europe, where direct and indirect aerosol effects on surface solar radiation drive the SAT long‐term trend and decadal variations, over CEA atmospheric circulation response to aerosols outside Asia plays an important role. Aerosol‐forced anomalous low‐level low pressure in mid‐latitude Eurasia may influence the SAT anomalies downstream over mid‐latitude Asia, including a warm anomaly around CEA. The results suggest that caution is needed in attributing SAT changes around CEA to anthropogenic aerosols from Asia.

Differences in East Asian summer monsoon responses to Asian aerosol forcing under different emission inventories

Opposite anthropogenic aerosol emission trends in Asia can lead to different responses of the climate. Here, we examined the responses of the East Asian summer monsoon (EASM) to changes in Asian anthropogenic aerosol emissions during 2006–2014 using a global aerosol/atmospheric chemistry–climate coupled model (BCC_AGCM2.0_CUACE/Aero) with two sets of emission inventories: the Community Emissions Data System (CEDS) inventory adopted by the Coupled Model Intercomparison Project Phase 6 (CMIP6) and the inventory developed at Peking University (PKU). The changes in Asian anthropogenic aerosol emissions during 2006–2014 between the two inventories were remarkably different, particularly in eastern China where completely opposite trends were observed (i.e., increase in the CEDS inventory, but significant reduction in the PKU inventory). The perturbation simulations with the Asian anthropogenic aerosol forcing from the two inventories showed opposite changes in aerosol optical depth, aerosol effective radiative forcing, cloud liquid water path, and total cloud cover in eastern China. The simulated ‘dipole-type’ changes (i.e., increase in India but decrease in China) in Asian aerosols and the resulting changes in local radiation budget under the PKU inventory were consistent with the corresponding observations. The summer surface temperatures over eastern China decreased by 0–0.4 K because of the Asian anthropogenic aerosol forcing under the CEDS inventory, while they increased by 0.1–0.8 K under the PKU inventory. The weakening of the EASM index caused by the Asian aerosol forcing under the PKU inventory was twofold greater than that under the CEDS inventory (−0.4 vs. −0.2). The Asian ‘dipole-type’ aerosol forcing contributed to the observed summer ‘southern drought and northern flood’ phenomenon in eastern China during 2006–2014. The slow ocean-mediated response to the regional ‘dipole-type’ aerosol forcing dominated the weakening of the EASM circulation and the precipitation changes in eastern China in the total response. This study further confirms that the biases in anthropogenic aerosol emissions over Asia can affect the CMIP6-based regional climate attribution.

The Solubility and Deposition Flux of East Asian Aerosol Metals in the East China Sea: The Effects of Aeolian Transport Processes

The Solubility and Deposition Flux of East Asian Aerosol Metals in the East China Sea: The Effects of Aeolian Transport Processes