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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]

Black carbon (BC) aerosol is a significant, short-lived climate forcing agent. To further understand the effects of BCs on the regional climate, the warming effects of BCs from residential, industrial, power and transportation emissions are investigated in Asian regions during summer using the state-of-the-art regional climate model RegCM4. BC emissions from these four sectors have very different rates and variations. Residential and industrial BCs account for approximately 85% of total BC emissions, while power BCs account for only approximately 0.19% in Asian regions during summer. An investigation suggests that both the BC aerosol optical depth (AOD) and direct radiative forcing (DRF) are highly dependent on emissions, while the climate effects show substantial nonlinearity to emissions. The total BCs AOD and clear-sky top of the atmosphere DRF averaged over East Asia (100–130°E, 20–50°N) are 0.02 and + 1.34 W/m2, respectively, during summer. Each sector's BC emissions may result in a warming effect over the region, leading to an enhanced summer monsoon circulation and a subsequent local decrease (e.g., northeast China) or increase (e.g., south China) in rainfall in China and its surrounding regions. The near surface air temperature increased by 0.2 K, and the precipitation decreased by approximately 0.01 mm/day in east China due to the total BC emissions. The regional responses to the BC warming effects are highly nonlinear to the emissions, which may be linked to the influences of the perturbed atmospheric circulations and climate feedback. The nonuniformity of the spatial distribution of BC emissions may also have significant influences on climate responses, especially in south and east China. The results of this study could aid us in better understanding BC effects under different emission conditions and provide a scientific reference for developing a better BC reduction strategy over Asian regions. [ABSTRACT FROM AUTHOR]

An interactive system coupling the Beijing Climate Center atmospheric general circulation model (BCC_AGCM2.0.1) and the Canadian Aerosol Module (CAM) with updated aerosol emission sources was developed to investigate the global distributions of optical properties and direct radiative forcing (DRF) of typical aerosols and their impacts on East Asian climate. The simulated total aerosol optical depth (AOD), single scattering albedo, and asymmetry parameter were generally consistent with the ground-based measurements. Under all-sky conditions, the simulated global annual mean DRF at the top of the atmosphere was −2.03 W m for all aerosols including sulfate, organic carbon (OC), black carbon (BC), dust, and sea salt; the global annual mean DRF was −0.23 W m for sulfate, BC, and OC aerosols. The sulfate, BC, and OC aerosols led to decreases of 0.58° and 0.14 mm day in the JJA means of surface temperature and precipitation rate in East Asia. The differences of land-sea surface temperature and surface pressure were reduced in East Asian monsoon region due to these aerosols, thus leading to the weakening of East Asian summer monsoon. Atmospheric dynamic and thermodynamic were affected due to the three types of aerosol, and the southward motion between 15°N and 30°N in lower troposphere was increased, which slowed down the northward transport of moist air carried by the East Asian summer monsoon, and moreover decreased the summer monsoon precipitation in south and east China. [ABSTRACT FROM AUTHOR]