Physical Research Laboratory, Ahmedabad, 380009, India.
Indian Centre for Climate and Societal Impacts Research, Kachchh, 370465, India.
Environ Sci Pollut Res Int. 2016 Jun;23(11):11109-11128. doi: 10.1007/s11356-016-6254-8. Epub 2016 Feb 26.
Mixing can influence the optical, physical, and chemical characteristics of aerosols, which in turn can modify their life cycle and radiative effects. Assumptions on the mixing state can lead to uncertain estimates of aerosol radiative effects. To examine the effect of mixing on the aerosol characteristics, and their influence on radiative effects, aerosol mixing states are determined over four environmentally distinct locations (Karachi, Gwangju, Osaka, and Singapore) in Asia, an aerosol hot spot region, using measured spectral aerosol optical properties and optical properties model. Aerosol optical depth (AOD), single scattering albedo (SSA), and asymmetry parameter (g) exhibit spectral, spatial, and temporal variations. Aerosol mixing states exhibit large spatial and temporal variations consistent with aerosol characteristics and aerosol type over each location. External mixing of aerosol species is unable to reproduce measured SSA over Asia, thus providing a strong evidence that aerosols exist in mixed state. Mineral dust (MD) (core)-Black carbon (BC) (shell) is one of the most preferred aerosol mixing states. Over locations influenced by biomass burning aerosols, BC (core)-water soluble (WS, shell) is a preferred mixing state, while dust gets coated by anthropogenic aerosols (BC, WS) over urban regions influenced by dust. MD (core)-sea salt (shell) mixing is found over Gwangju corroborating the observations. Aerosol radiative forcing exhibits large seasonal and spatial variations consistent with features seen in aerosol optical properties and mixing states. TOA forcing is less negative/positive for external mixing scenario because of lower SSA. Aerosol radiative forcing in Karachi is a factor of 2 higher when compared to Gwangju, Osaka, and Singapore. The influence of g on aerosol radiative forcing is insignificant. Results emphasize that rather than prescribing one single aerosol mixing state in global climate models regionally and temporally varying aerosol mixing states should be included for more accurate assessment of aerosol radiative effects.
混合可以影响气溶胶的光学、物理和化学特性，进而改变其生命周期和辐射效应。对混合状态的假设可能导致气溶胶辐射效应的不确定估计。为了研究混合对气溶胶特性的影响及其对辐射效应的影响，在亚洲四个具有不同环境特征的地点（卡拉奇、光州、大阪和新加坡），利用测量的光谱气溶胶光学特性和光学特性模型，确定了气溶胶混合状态。气溶胶光学深度（AOD）、单次散射反照率（SSA）和不对称参数（g）表现出光谱、空间和时间变化。气溶胶混合状态表现出大的空间和时间变化，与每个地点的气溶胶特性和气溶胶类型一致。气溶胶物种的外混合无法再现亚洲地区测量的 SSA，因此提供了气溶胶处于混合状态的有力证据。矿物粉尘（MD）（核）-黑碳（BC）（壳）是最常见的气溶胶混合状态之一。在受生物质燃烧气溶胶影响的地点，BC（核）-水溶性（WS，壳）是首选的混合状态，而在受粉尘影响的城市地区，粉尘则被人为气溶胶（BC、WS）覆盖。在受光州影响的地区发现了 MD（核）-海盐（壳）混合。气溶胶辐射强迫表现出与气溶胶光学特性和混合状态所见特征一致的大的季节性和空间变化。由于 SSA 较低，外混合情况下的 TOA 强迫作用不那么负/正。与光州、大阪和新加坡相比，卡拉奇的气溶胶辐射强迫高一个因子。g 对气溶胶辐射强迫的影响并不显著。结果强调，在全球气候模型中，不应规定单一的气溶胶混合状态，而应根据地区和时间变化的气溶胶混合状态进行更准确的气溶胶辐射效应评估。
