Studies on the Climate Effects of Black Carbon Aerosols in China and Their Sensitivity to Particle Size and Optical Parameters

In this paper, based on the principle of Mie scattering, we calculated the optical parameters of BC aerosols at different scales and then applied the new optical parameters to simulate the BC aerosols concentration distribution, radiative forcing, and their climate effects. We also compared the results of optical parameters of BC aerosols with homogeneous scales and analyzed the effect on climate. Compared with the conventional uniform-scheme optical parameterization, the concentrations of the first mode of BC aerosols simulated with the optical parameters that were recalculated based on the particle size are significantly higher, while the concentrations of the other modes and the total of BC aerosols are lower. In the respective of statistics, the changes of column burdens of BC in four modes are 0.085, -0.095, -0.089, -0.054 mg/m(2). The clear-sky TRF of BC are weakened in the value of 0.03 W/m(2) averaged over the domain, while the all-sky TRF of BC are enhanced of 0.06 W/m(2) in general. The warming effect of BC becomes weaker when using the new scheme by -0.04 K to -0.24 K. When using the new optical parameters scheme, the regional average surface concentrations of BC in four modes are 0.372, 0.264, 0.055 and 0.004 mu g/m(3), respectively. Especially, the first and the second mode account for as large as 53% and 38%. The surface concentration and column burden of total BC are 0.69 mu g/m(3) and 0.28 mg/m(2) can be dropped. The regional average direct RFs of BC at the top of the atmosphere are 0.49 W/m(2) under clear-sky and 0.36 W/m(2) under all-sky averaged over the domain. Over most areas of central China, North China, and East China, BC may increase the temperature in a range of 0.05 similar to 0.15 K, while over South China, BC shows cooling effect. In average, the precipitation variations caused by BC over East China, North China, South China, and Northeast China are -0.83, -0.05, -0.11, and -0.13 mm/d, respectively. As a whole, the variations of circulation, pressure, and temperature show a good correspondence.