中国地区气溶胶类型变化及其辐射效应研究

利用AERONET网站中国地区各区域多个站点长期的观测数据，通过各类气溶胶光学特性的差异（Extinction Angstrom Exponent，EAE；Single Scattering Albedo，SSA）将中国地区华北区域北京、香河站点，华东区域太湖站点，华南区域香港站点，西北区域SACOL站点气溶胶进行分类分析其气溶胶占比特征及年际变化，并进一步研究不同地区各类气溶胶光学及辐射特性差异.研究结果表明，不同地区各类气溶胶占比特征显著，华北区域北京、香河站点混合吸收型气溶胶Type5占比最多，分别占比35%、31%；其次为城市/工业型气溶胶Type3和Type4；华东区域以Type3、Type4和Type5三类气溶胶为主，分别占比32%、26%、25%；华南区域Type3、Type4气溶胶占比最为突出，占比分别达到46%、21%.西北区域Type5占比高达45%，出现高达34%的沙尘型气溶胶Type7.以不同地区各类气溶胶占比特征为基础，不同气溶胶的年际变化趋势差异较大.不同地区各类气溶胶光学特性参数（AOD（Aerosol Optical Depth）、EAE、SSA）年变化特征表明，华北、华东区域AOD减少、EAE变化小、SSA增大；华南区域整体AOD增大，但近年来AOD显著减少、EAE变化小、SSA增大；西北区域AOD增大、EAE增大、SSA减少，即除了西北区域外，其余区域环境空气质量逐渐好转，粒子尺度变化较小，吸收能力下降.地表气溶胶直接辐射强迫效率（ARFE-BOA）结果显示，除华东区域太湖站点外，Type1对地表的降温冷却作用最大，绝对值均大于210 W·m^-2，其次为Type2，即吸收型粒子对地表的贡献大于散射型粒子；关于ARFE-TOA的平均特征，Type4或Type7对大气顶的降温冷却作用最强，而各类气溶胶对大气层的加热作用与ARFE-BOA的平均特征类似，吸收型细粒子对大气层的加热作用较强.

A study of the spatiotemporal variation in aerosol types and their radiation effect in China

Based on the differences of aerosol optical properties (Extinction Angstrom Exponent, EAE, and Single Scattering Albedo, SSA) which were downloaded from the Aerosol Robotic Network (AERONET), the aerosol types at the sites in China (including Beijing and Xianghe in North China, Taihu in East China, Hong Kong in South China, and SACOL in Northwest China) were classified. The spatiotemporal variations in aerosol types and their radiation effect were further studied. The results showed that the average proportions of the eight aerosol types in each site were different. For the sites in North China, the Type5 (mainly mixed-absorbing aerosol) was the dominant aerosol type, accounting for 35% at Beijing and 31% at Xianghe, followed by Type3 and Type4 (mainly urban/industrial aerosols). At East China site, the Type3, Type4 and Type5 were the dominant aerosol types, accounting for 32%, 26% and 25% respectively. At South China site, the dominant aerosol types were Type3 (accounting for 46%) and Type4 (21%). However, Type5 accounted for up to 45% and 34% Type7 (dust aerosol) occurred at the Northwest China site. The trends in annual variations of the proportions of aerosol types in different regional sites were quite different. The annual Aerosol Optical Depth (AOD), EAE and SSA in different region also showed different variations tendencies. North China and East China sites illustrated that the annual AOD decreased, EAE changed little and SSA increased. The overall AOD and SSA in South China increased, while EAE showed little change and AOD decreased significantly in recent four years. However, the annul AOD and EAE increased while SSA decreased in Northwest China. Thus, except for the Northwest China, the air quality at other regional sites tended to be improved with the slightly change in particle size and the decreased in the absorption capacity of aerosol. Besides, the aerosol direct radiative forcing efficiency at the bottom of atmosphere (ARFE-BOA) illustrated that Type1 had the largest cooling effect except for Taihu site in East China, with the absolute values greater than 210 W·m^-2, followed by Type2. These indicated that the cooling effect of absorbing aerosols at the surface was greater than that of scattering aerosols. As for the average characteristics of aerosol direct radiative forcing efficiency at the top of atmosphere (ARFE-TOA), Type4 or Type7 had the greatest cooling effect at the top of atmospheric. The effect of aerosol types heating the atmosphere was similar to that of ARFE-BOA, that is, absorbing fine-mode particles had a strong heating effect on the atmosphere.