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In the context of China's "dual carbon" goal, emissions of air pollutants are expected to significantly decrease in the future. Thus, the direct climate effects of black carbon (BC) aerosols in East Asia are investigated under this goal using an updated regional climate and chemistry model. The simulated annual average BC concentration over East Asia is approximately 1.29 μg/m3 in the last decade. Compared to those in 2010–2020, both the BC column burden and instantaneous direct radiative forcing in East Asia decrease by more than 55% and 80%, respectively, in the carbon peak year (2030s) and the carbon neutrality year (2060s). Conversely, the BC effective radiative forcing (ERF) and regional climate responses to BC exhibit substantial nonlinearity to emission reduction, possibly resulting from different adjustments of thermal‐dynamic fields and clouds from BC‐radiation interactions. The regional mean BC ERF at the tropopause over East Asia is approximately +1.11 W/m2 in 2010–2020 while negative in the 2060s. BC‐radiation interactions in the present‐day impose a significant annual mean cooling of −0.2 to −0.5 K in central China but warming +0.3 K in the Tibetan Plateau. As China's BC emissions decline, surface temperature responses show a mixed picture compared to 2010–2020, with more cooling in eastern China and Tibet of −0.2 to −0.3 K in the 2030s, but more warming in central China of approximately +0.3 K by the 2060s. The Indian BC might play a more important role in East Asian climate with reduction of BC emissions in China. Plain Language Summary: Black carbon (BC) aerosols, which are among the air pollutants that will be reduced in China under the "dual carbon" goal, can have an impact on the regional climate by absorbing solar radiation. We use a regional climate model to simulate the climate effect of BC over East Asia under the "dual carbon" goal of China. The results showed that the BC concentration and column burden in East Asia, as well as the instantaneous direct radiative forcing, will decrease significantly under future regional emission reduction policies. However, the effective radiative forcing of BC and regional climate responses do not exhibit simple linear relationships with emissions. The BC‐induced atmospheric thermal‐dynamic anomalies are the main drivers of this nonlinearity. Similarly, BC emissions from India might also influence the East Asian climate. Key Points: The East Asian black carbon (BC) loadings and instantaneous direct radiative forcings significantly decrease under the "dual carbon" goal of ChinaThe BC induced regional climate changes show nonlinear responses to the BC emission reductionThe Indian BC might play an increasingly important role in East Asian climate with decreasing BC emissions in China [ABSTRACT FROM AUTHOR]

The interactions between the terrestrial biosphere, atmospheric chemistry, and climate involve complex feedbacks that have traditionally been modeled separately. We present a new framework that couples the Yale Interactive terrestrial Biosphere (YIBs) model, a dynamic plant-chemistry model, with the RegCM-Chem model. RegCM-Chem–YIBs integrates meteorological variables and atmospheric chemical composition from RegCM-Chem with land surface parameters from YIBs. The terrestrial carbon flux calculated by YIBs is fed back into RegCM-Chem interactively, thereby representing the interactions between fine particulate matter (PM 2.5), ozone (O 3), and carbon dioxide (CO 2). For testing purposes, we carry out a 1-year simulation (2016) at a 30 km horizontal resolution over East Asia with RegCM-Chem–YIBs. The model accurately captures the spatio-temporal distribution of climate, chemical composition, and ecological parameters. In particular, the estimated O 3 and PM 2.5 are consistent with ground observations, with correlation coefficients (R) of 0.74 and 0.65, respectively. The simulated CO 2 concentration is consistent with observations from six sites (R ranged from 0.89 to 0.97) and exhibits a similar spatial pattern when compared with carbon assimilation products. RegCM-Chem–YIBs produces reasonably good gross primary productivity (GPP) and net primary productivity (NPP), showing seasonal and spatial distributions consistent with satellite observations, and mean biases (MBs) of 0.13 and 0.05 kg C m -2 yr -1. This study illustrates that RegCM-Chem–YIBs is a valuable tool to investigate coupled interactions between the terrestrial carbon cycle, atmospheric chemistry, and climate change at a higher resolution on a regional scale. [ABSTRACT FROM AUTHOR]

The interactions between the terrestrial biosphere, atmospheric chemistry, and climate involve complex feedbacks that have traditionally been modeled separately. We present a new framework that couples the Yale Interactive terrestrial Biosphere (YIBs), a dynamic plant-chemistry model, with the RegCM-Chem model. RegCM-Chem-YIBs integrates meteorological variables and atmospheric chemical composition from RegCM-Chem with land surface parameters from YIBs. The terrestrial carbon flux calculated by YIBs, are fed back into RegCM-Chem interactively, thereby representing the interactions between fine particulate matter (PM2.5), ozone (O3), and carbon dioxide (CO2). For testing purposes, we carry out a one-year simulation (2016) at a 30 km horizontal resolution over East Asia with RegCM-Chem-YIBs. The model accurately captures the spa-tio-temporal distribution of climate, chemical composition, and ecological parameters. In particular, the estimated O3 and PM2.5 are consistent with ground observations, with correlation coefficients (R) of 0.74 and 0.65, respec-tively. The simulated CO2 concentration is consistent with observations from six sites (R ranged from 0.89 to 0.97) and exhibits a similar spatial pattern when compared to carbon assimilation products. RegCM-Chem-YIBs produces reasonably good gross primary productivity (GPP) and net primary productivity (NPP), showing seasonal and spatial distributions consistent with satellite observations, and mean biases (MBs) of 0.13 and 0.05 kg C m-2 year-1. This study illustrates that the RegCM-Chem-YIBs is a valuable tool to investigate coupled interactions between the terrestrial carbon cycle, atmospheric chemistry, and climate change at a higher resolution in regional scale. [ABSTRACT FROM AUTHOR]

Aerosol mixtures, which are still unclear in current knowledge, may cause large uncertainties in aerosol climate effect assessments. To better understand this research gap, a well-developed online coupled regional climate-chemistry model is employed here to investigate the influences of different aerosol mixing states on the direct interactions between aerosols and the East Asian summer monsoon (EASM). The results show that anthropogenic aerosols have high-level loadings with heterogeneous spatial distributions in East Asia. Black carbon aerosol loading accounts for more than 13% of the totals in this region in summer. Thus, different aerosol mixing states cause very different aerosol single scattering albedos, with a variation of 0.27 in East Asia in summer. Consequently, the sign of the aerosol instantaneous direct radiative forcing at the top of the atmosphere is changed, varying from − 0.95 to + 1.50 W/m2 with increasing internal mixing aerosols. The influence of aerosol mixtures on regional climate responses seems to be weaker. The EASM circulation can be enhanced due to the warming effect of anthropogenic aerosols in the lower atmosphere, which further induces considerable aerosol accumulation associated with dynamic field anomaly, decrease in rainfall and so on, despite aerosol mixtures. However, this interaction between aerosols and the EASM will become more obvious if the aerosols are more mixed internally. Additionally, the differences in aerosol-induced EASM anomalies during the strongest and weakest monsoon index years are highly determined by the aerosol mixing states. The results here may further help us better address the environmental and climate change issues in East Asia. [ABSTRACT FROM AUTHOR]

Absorbing aerosols have significant influences on tropospheric photochemistry and regional climate change. Here, the direct radiative effects of absorbing aerosols at the major AERONET sites in East Asia and corresponding impacts on near-surface photochemical processes were quantified by employing a radiation transfer model. The average annual aerosol optical depth (AOD) of sites in China, Korea, and Japan was 1.15, 1.02 and 0.94, respectively, and the corresponding proportion of absorbing aerosol optical depth (AAOD) was 8.61%, 6.69%, and 6.49%, respectively. The influence of absorbing aerosol on ultraviolet (UV) radiation mainly focused on UV-A band (315–400 nm). Under the influence of such radiative effect, the annual mean near-surface J[NO2] (J[O1D]) of sites in China, Korea, and Japan decreased by 16.95% (22.42%), 9.61% (13.55%), and 9.63% (13.79%), respectively. In Beijing–Tianjin–Hebei (BTH) and Yangtze River Delta (YRD) region, the annual average AOD was 1.48 and 1.29, and the AAOD was 0.14 and 0.13, respectively. The UV radiative forcing caused by aerosols dominated by black carbon (BC-dominated aerosols) on the surface was −3.19 and −2.98 W m−2, respectively, accounting for about 40% of the total aerosol radiative forcing, indicating that the reduction efficiency of BC-dominated aerosols on solar radiation was higher than that of other types of aerosols. The annual mean J[NO2] (J[O1D]) decreased by 14.90% (20.53%) and 13.71% (18.20%) due to the BC-dominated aerosols. The daily maximum photolysis rate usually occurred near noon due to the diurnal variation of solar zenith angle and, thus, the daily average photolysis rate decreased by 2–3% higher than that average during 10:00–14:00. [ABSTRACT FROM AUTHOR]

Atmospheric black carbon (BC) in the Tibetan Plateau (TP) can largely impact regional and global climate. Still, studies on the inter-annual variation in atmospheric BC over the TP and associated variation in BC sources and controlling factors are rather limited. In this study, we characterize the variations in atmospheric BC over the TP surface layer through analysis of 20-year (1995–2014) simulations from a global chemical transport model, GEOS-Chem. The results show that surface BC concentrations over the TP vary largely in space and by season, reflecting complicated interplays of BC sources from different origins. Of all areas in the TP, surface BC concentrations are highest over the eastern and southern TP, where surface BC is susceptible to BC transport from East Asia and South Asia, respectively. Applying a backward-trajectory method that combines BC concentrations from GEOS-Chem and trajectories from the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, we assess the contributions of worldwide source regions to surface BC in the TP. We estimate that on the 20-year average, 77 % of surface BC in the TP comes from South Asia (43 %) and East Asia (35 %). Regarding seasonal variation in non-local influences, South Asia and East Asia are dominant source regions in winter and summer, respectively, in terms of the amount of BC imported. However, in terms of affected areas in the TP, South Asia is the dominant contributor throughout the year. Inter-annually, surface BC over the TP is largely modulated by atmospheric transport of BC from non-local regions year-round and by biomass burning in South Asia, mostly in spring. We find that the extremely strong biomass burning in South Asia in the spring of 1999 greatly enhanced surface BC concentrations in the TP (31 % relative to the climatology). We find that the strength of the Asian monsoon correlates significantly with the inter-annual variation in the amount of BC transported to the TP from non-local regions. In summer, a stronger East Asian summer monsoon and a stronger South Asian summer monsoon tend to, respectively, lead to more BC transport from central China and north-eastern South Asia to the TP. In winter, BC transport from central China is enhanced in years with a strong East Asian winter monsoon or a strong Siberian High. A stronger Siberian High can also bring more BC from northern South Asia to the TP. This study underscores the impacts of atmospheric transport and biomass burning on the inter-annual variation in surface BC over the TP. It reveals a close connection between the Asian monsoon and atmospheric transport of BC from non-local regions to the TP. [ABSTRACT FROM AUTHOR]

With the rapid urbanization and the implementation of a series of air pollution control measures, significant changes have occurred in the emission of fine particulate matter (PM 2.5), ozone (O 3) precursors, and CO 2 in China. In this study, we comprehensively assess the impact of emission variations on the East Asian Summer Monsoon (EASM) climate from 2008 to 2018 using a regional-chemistry-ecology model RegCM-Chem-YIBs. The investigations indicated a strengthening of the EASM from 2008 to 2018, with all four EASM Indices exhibiting an increase trend ranging from 0.08 to 1.09 per year based on the simulations. Since 2008, alterations in the emissions of PM 2.5 and O 3 precursors in 2013 and 2018 led to a rise in near-surface temperatures in China by 0.5–1.5 K, thereby enhancing the EASM. Conversely, the changed CO 2 emissions, through its influence on radiative balance and altering BVOCs (Biogenic Volatile Organic Compounds) emissions via its effect on vegetation growth, decreased temperatures by 0.5–1.5 K, thus weakening the EASM. However, when considering the combined effects of total emissions changes in PM 2.5 , O 3 precursors, and CO 2 , surface temperatures increased by 0.5–2 K, ultimately strengthening the EASM. In addition, compared to 2013, EASM was strongly enhanced in 2018 due to the notable increase in CO 2 and significant reduction of PM 2.5 and O 3 precursors. Our study underscores the significant influence of variations in PM 2.5 , O 3 precursors, and CO 2 emissions on EASM climate and emphasizes the importance of coordinated governance of air pollution and climate change. • The emissions of PM 2.5 , O 3 , and CO 2 have undergone considerable changes. • The EASM has strengthened from 2008 to 2018. • The variations in PM 2.5 , O 3 , and CO 2 emissions significant influence the EASM. [ABSTRACT FROM AUTHOR]

East Asia (EA) has always been a highly concern region for human-induced climate change. In this study, a well-developed regional model RegCM4 is employed to investigate the influences of major anthropogenic aerosol (MAA, including sulfate and primary carbonaceous aerosols) variations from 2007 to 2020 on East Asian climates in winter. Results indicate that high MAA loadings in EA in winter mainly appear in Central to Eastern China. In most area of Asia (5°-55°N, 70°-140°E), the multi-year (2007–2020) mean instantaneous direct and total effective radiative forcing (IDRF and ERF) induced by MAAs are −4.22 and −3.90 W·m−2 at the surface in winter, which are 2.29 and 1.96 times of those at the tropopause. In polluted area from southwest to center China (SWCC, 27–33°N, 102–115°E), these forcings are much stronger, which causes a dimmer, cooler and drier surface and further stabilizes the lower atmosphere. The multi-year mean sunshine duration, surface air temperature, precipitation, and boundary layer thickness are changed by −20.32 min·d−1, −0.33 K, −0.08 mm·d−1, and −12.51 m, respectively in SWCC in winter. Both the aerosol surface IDRF and ERF are weakened by above 30% in SWCC in winter since the Action Plan for Air Pollution Prevention and Control was carried out, which results in less surface dimming and cooling by 9.4 min·d−1 and 0.23 K, respectively. During the most outbreak period in COVID-19 epidemic, the aerosol surface IDRF is weakened by approximately 46.87% compared to that before 2013 in SWCC, which may offset the aerosol cooling effect by 0.28 K. • Effects of emission reductions on the ARi and ACi are investigated in East Asia in winter. • ARi and ACi in East Asia in winter likely cause a cooler and drier surface, and a more stable PBL. • The aerosol cooling effect in East Asia in winter is weakened since APPCAP/COVID-19. [ABSTRACT FROM AUTHOR]

Ozone (O 3) and fine particulate matter (PM 2.5) are the major air pollutants, and CO 2 is a critical greenhouse gas in East Asia. They three are active species in terms of radiation. Most importantly, both O 3 and PM 2.5 can interact with CO 2 through the terrestrial ecosystem, thus having effects on the regional climate. This study investigated the mutual interactions among O 3 , PM 2.5 , and CO 2 on the East Asia summer monsoon climate using the coupling regional climate-chemistry-ecology model, RegCM-Chem-YIBs. Two numerical experiments were performed with and without involving the interactions among the three species. The investigations showed that the mutual interactions finally resulted in changes to surface PM 2.5 , O 3 , and CO 2 of -6∼-2 μg/m3, 4∼6 μg/m3, and 3∼5 ppm, respectively, in northern China. While in southern China, surface PM 2.5 , O 3 , and CO 2 varied in the range of 2∼4 μg/m3, 1∼2 μg/m3, and -4∼-2 ppm. Surface downward shortwave radiation flux (SWF) and longwave radiation flux (LWF) increased in northern China, whereas showed decreasing in southern China. The lower atmosphere was warmed by 1∼2 K in north China, enlarging the air temperature gradient between land and sea, inducing easterly and southerly winds at 850 hpa in the region. On the contrary, surface cooling (-2∼-1K) exhibited northerly wind anomalies in southern China. The results indicated that the mutual interactions among the three species could significantly impact regional climate. We argue that future simulations should consider these interactions to better predict air pollution and climate changes in the target region. This work could help to comprehensively understand the climate effects of the mutual interactions among O 3 , PM 2.5 , and CO 2. The findings provide a scientific reference for the collaborative governance of regional climate and air pollution in East Asia. • Mutual interactions among O 3 , PM 2.5 , and CO 2 are considered in RegCM-Chem-YIBs. • More realistic simulations on meteorolgy and air pollution in East Asia were found when mutual interactions were involved. • The mutual interactions can significantly modify the summer monsoon climate in East Asia. [ABSTRACT FROM AUTHOR]