气溶胶的气候效应是全球气候变化研究中不确定性最大的因素。气溶胶吸湿性影响气溶胶的光学特性以及活化成为云凝结核的能力，影响气溶胶的直接和间接辐射强迫。目前国内对于大气气溶胶吸湿性观测研究相对缺乏，尤其是长期的、系统的研究更为缺乏。本项目拟使用气溶胶吸湿增长测量仪（H-TDMA）、黑碳仪、浊度计、气溶胶离子成分分析仪、元素碳/有机碳分析仪等设备，开展长期的珠江三角洲大气气溶胶吸湿性、光学特性和化学特性同步观测，并结合Mie散射模式组成干、湿、环境状态下的气溶胶光学闭合实验。项目预期能系统地表征珠三角地区大气气溶胶的吸湿增长因子和混合状态，包括日、季和不同天气条件下的变化特征，揭示影响气溶胶吸湿性变化的主导因素；基于观测数据，使用修正后的Mie散射模式组成光学闭合实验，求解、验证和评估不同湿度状态下的光学模型及相关假设，揭示气溶胶吸湿性对光学性质的影响。所得结果将深化珠三角地区大气灰霾形成和转化

The climate effect of aerosols is the largest uncertainty factor in the climate change study of the globe. Aerosols hygroscopicity affects their optical properties and their capability in activating to become cloud condensation nuclei, resulting in direct and indirect radioactive forcing effects of these aerosols.The observational study of hydroscopicity of aerosols is rather limited in mainland China, especially long-term, systematic studies.This project uses Hygroscopicity-Tandem Differential Mobility Analyzer(H-TDMA), Aethalometer, Nephelometer , aerosol ion composition analyzer, EC/OC analyzer, etc. to conduct a long-term study of aerosol hydroscopicity, optical properties and chemical characteristics at the same time over Pearl River Delta. It is also combined with Mie scattering model for a closure experiment of the optical properties of aerosols under dry, wet and ambient conditions. The project is expected to systematically give the growth factor and mixing state of aerosols in the Pearl River Delta area, including the variations in characteristics in diurnal scale, seasonal scale and different weather conditions. It also depicts the major factors affecting the changes in the hygroscopicity of aerosols. Based on the observational data and using the revised Mie scattering model, this project solves, verifies and assesses the optical properties of aerosol and the associated assumptions under different humidity conditions, displaying the effect of hygroscopicity on the optical properties of the aerosols. The results so obtained deepen our knowledge on the formation and transformation mechanisms of haze in the atmosphere of the Pearl River Delta area.