RegCM4.3, a high-resolution regional climate model, which includes five kinds of aerosols (dust, sea salt, sulfate, black carbon and organic carbon), is employed to simulate the East Asian summer monsoon (EASM) from 1995 to 2010 and the simulation data are used to study the possible impact of natural and anthropogenic aerosols on EASM. The results show that the regional climate model can well simulate the EASM and the spatial and temporal distribution of aerosols. The EASM index is reduced by about 5% by the natural and anthropogenic aerosols and the monsoon onset time is also delayed by about a pentad except for Southeast China. The aerosols heat the middle atmosphere through absorbing solar radiation and the air column expands in Southeast China and its offshore areas. As a result, the geopotential height decreases and a cyclonic circulation anomaly is generated in the lower atmosphere. Northerly wind located in the west of cyclonic circulation weakens the low-level southerly wind in the EASM region. Negative surface radiative forcing due to aerosols causes downward motion and an indirect meridional circulation is formed with the low-level northerly wind and high-level southerly wind anomaly in the north of 25 degrees N in the monsoon area, which weakens the vertical circulation of EASM. The summer precipitation of the monsoon region is significantly reduced, especially in North and Southwest China where the value of moisture flux divergence increases.

The climate effects of black carbon (BC) aerosols are sensitive to BC size distributions and this sensitivity over China is studied using a regional climate model, namely RIEMS2.0. A new size-resolved scheme is developed based on observational data. The simulated BC concentrations with the new scheme are better compared with the observation than the previous uniform scheme, which is likely to overestimate BC concentrations, radiative forcings, and warming effects in many regions of China due to its simple assumption on BC size. The simulation with the size-resolved scheme suggests a reduction of the all-sky radiative forcing of BC at the top of atmosphere (TOA) by 0-0.25 W m(-2) over the most study domain. Correspondingly, the warming effect of BC is weakened by -0.04 to -0.16 K over most parts of South China and North China. The difference in BC-induced precipitation between the two schemes varies irregularly from region to region, ranging from -2.8 to 2.8 mm d(-1). With the size-resolved scheme, the BC radiative properties and the climate effects are reassessed and the means (ranges) over the study domain are summarized as follows. The annual mean surface concentration of BC is 0.88 mu g/m(3), ranging from 1 to 8 mu g/m(3) over North China and Central China. The all-sky and clear-sky radiative forcings of BC at the TOA are 0.43 and 0.39 W/m(2), respectively. Over most parts of Southwest China, Central China, and North China, the BC warming effect prevails, with enhanced temperature of 0.04-028 K. BC aerosols usually enhance precipitation in South China and North China, ranging from 0.40 to 2.8 mm d(-1). (C) 2016 Elsevier B.V. All rights reserved.

The Regional Integrated Environmental Model System (RIEMS2.0) and the emission data of 2006 and 2020 were used to simulate the distributions and climate effects of anthropogenic aerosols sulfate, nitrate, black carbon and organic carbon for the entire year of 2006. The results show that: (1)The regional average column burdens of sulfate in 2006 are the largest among the anthropogenic aerosols, followed by organic carbon, nitrate, and black carbon, with the regional average value of 6.0, 4.0, 1.3 and 0.3 mg/m(2), respectively. (2)The regional average radiative forcing (RF) of sulfate, nitrate, organic, and black carbon are -1.32, -0.60, -0.40, and 0.28 W/m(2), respectively. The negative RF of sulfate, nitrate, and organic carbon are larger than the positive RF of black carbon. The net RF of anthropogenic aerosol is -1.96 W/m(2). (3) The radiative effects and temperature change caused by anthropogenic aerosols are sensitive to emission inventory. The column burdens and climate effects of anthropogenic aerosols are strongly influenced by the emission scenarios. In future, the larger emission intensity may cause more considerable negative RF, temperature drop and precipitation reduction.