京津冀区域重霾过程分档耦合模式模拟及快速成霾机理研究

In recent years, the emissions of air pollutants in China have always been very high, and therefore the formation of a regional severe haze is quite rapid under the static and stable weather condition, especially in beijing-tianjin-hebei region. During the rapid haze-forming processes, two mechanisms are important: new particles formation and rapid growth before the beginning of the haze; the positive feedback mechanism between the haze and the atmospheric boundary layer after the haze beginning, but a clear and quantitative understanding is lacked about the two mechanisms. Traditional air quality models are imperfect to simulate the two mechanisms: they use a few modals or bins to characterize the aerosol size distribution, which cannot reflect the new particle formation and the complex changes of the particle size distribution, and also the aerosol optical and radiation characteristics; and besides few models consider the aerosol radiation effects to the atmospheric boundary layer. So the simulations of the severe haze processes have large biases. This project is proposed on the basis of the existing research, using the aerosol physical characteristics calculated by the detailed sectional model NAQPMS-APM, to improve the aerosol optical module of the two-way coupled meteorology-chemical model WRF-NAQPMS, and then set up a new sectional and coupled model WRF-NAQPMS-APM. The typical severe haze process over beijing-tianjin-hebei region will be simulated using the new model, combined with sensitivity analysis and process analysis techniques, to quantify the impacts of the foregoing two mechanisms on the rapid haze-forming process, and then to clarify the reasons of rapid haze-forming over beijing-tianjin-hebei region.

近年来，我国大气污染物排放量居高不下，导致静稳条件下短时间内可形成区域性重度灰霾，京津冀地区尤为严重。快速成霾过程中有两个机制较为关键：灰霾发生前新粒子大量生成并快速增长机制、灰霾开始后大气边界层与灰霾之间正反馈机制，但对两种机制还缺乏清晰的定量认识。可量化上述机制重要性的空气质量模式，目前还存在不足：气溶胶粒径谱由少数几个模态或档来表征，不能准确反映新粒子生成和粒径谱的复杂变化，同时也较少考虑气溶胶辐射效应对边界层气象的影响，因此难以准确模拟两种机制。本项目拟在已有研究基础上，利用气溶胶精细分档模式NAQPMS-APM计算的粒径谱等气溶胶微物理特性，改进双向耦合气象-化学模式WRF-NAQPMS的气溶胶光学模块，建立新一代分档耦合模式WRF-NAQPMS-APM。利用新模式对典型重霾过程进行模拟，结合敏感性分析和过程分析技术，量化前述机制在快速成霾过程中贡献，阐明京津冀区域快速成霾机理。

近年来，我国大气污染物排放量居高不下，导致静稳天气下短时内可形成区域性重度灰霾，京津冀地区尤为严重。本研究在中国自主空气质量模式NAQPMS的基础上，利用气溶胶详细分档模式NAQPMS-APM计算的粒径谱等气溶胶微物理特性，改进了双向耦合气象-化学模式WRF-NAQPMS的气溶胶光学模块，研发了新一代分档耦合模式WRF-NAQPMS-APM。由于气溶胶吸湿增长对气溶胶的光学和辐射特性有非常重要的影响，而目前最常用的气溶胶吸湿增长方案仅适用于高相对湿度情形，因此，本项目提出了一个新的、普遍适用于高、低相对湿度的气溶胶吸湿增长方案。该方法可广泛应用于灰霾能见度、气溶胶辐射效应等方面的研究。基于新研发的双向耦合模式，量化了大气边界层与灰霾之间正反馈机制对空气污染形成的重要作用。本研究结果有利于提高京津冀地区空气质量预测的精度，为制定高效的空气污染管控措施提供科学依据。