南亚黑碳气溶胶跨境传输及其对青藏高原气候影响的数值模拟研究

Tibetan Plateau is adjacent to the region of anthropogenic emissions over South Asia. Black carbon which emitted from South Asia transports in the long range, and finally reaches the inland of Tibetan Plateau. The results based on the observations show that the concentrations of black carbon in the snow and ice are increased in recent decades in the east and south plateau, which may lead to change the process of hydrological cycle in the way of accelerating glaciers melt and shortening snow cover duration in the Tibetan Plateau. However, the amount of trans-boundary transport of black carbon from South Asia is not clear and the knowledge of its impact on climate over the Tibetan Plateau is still limited. This project will use a high-resolution regional climate model RegCM4 coupled with a chemical-aerosol module to simulate the transport process of black carbon in a long period in South Asia. We plan to investigate the contributions of trans-boundary transport of black carbon from South Asia through different sensitivity experiments. The studies are focused on the five black carbon emission inventories, and the uncertainties will be discussed by the comparison of simulation results under different inventories. Finally, we will investigate the climate effects of black carbon in the Tibetan Plateau. The results will help to provide a scientific basis for the assessment of the impact of human activities on climate change over the Tibetan Plateau.

青藏高原毗邻南亚污染物排放源区，南亚黑碳气溶胶通过远距离传输，可以到达高原内陆地区。观测事实表明近几十年青藏高原东部和南部雪冰中黑碳含量呈明显上升的趋势，这可能导致高原冰川加速融化和积雪持续时间缩短，最终影响青藏高原的水循环过程。目前对南亚黑碳气溶胶跨境传输量及其对青藏高原气候变化的影响还没有较清晰和统一的认识。本研究拟使用耦合大气化学过程的高分辨率区域气候模式RegCM4，通过不同的敏感试验，模拟南亚黑碳气溶胶的传输过程，定量评估其跨境传输的贡献率；在模式中引入五种不同的黑碳排放清单，对比分析模拟结果的不确定性，在此基础上探讨南亚黑碳排放产生的气候效应，为评估人类活动对青藏高原气候变化的影响提供科学依据。

黑碳属强吸光性气溶胶，可吸收太阳短波辐射，对大气有显著的增温作用。当黑碳颗粒物沉降到雪冰表面之后形成吸光性杂质，导致雪冰反照率降低，间接增大雪冰对太阳辐射的吸收效率，雪冰吸收了更多的太阳辐射并在地表产生正的辐射强迫，最终导致冰川加速融化和积雪持续时间缩短，是冰冻圈快速变化的关键过程之一。当前，大气中的黑碳多来源于人类活动，而青藏高原毗邻南亚污染物排放源区，黑碳经过大气传输，可到达高原内陆区域，近几十年青藏高原东部和南部雪冰中黑碳含量呈显著上升的趋势。之前对青藏高原人为排放黑碳的外源输送，特别是南亚大气污染物的贡献，及对高原气候、冰冻圈变化的影响，还没有较清晰和统一的认识，缺乏全面定量评估的结果。本研究使用高分辨率区域气候-大气化学模型，通过与观测数据的对比，系统性论证了模型在高原的适用性；在此基础上，模拟了青藏高原及周边区域黑碳时空分布、传输和沉降过程，揭示污染物扩散的机制，评估了大气黑碳的气候效应；对比了自然源粉尘和人为源黑碳对青藏高原气候的影响；通过多个敏感试验，定量估算了不同区域排放对高原黑碳外源输送的贡献率；在区域气候模式中耦合了雪冰-气溶胶辐射传输模块，评估了黑碳对雪冰反照率、辐射强迫及消融过程的影响。以上研究成果，在Climate Dynamics, International Journal of Climatology, Atmospheric Research等期刊发表论文5篇（项目负责人为第一作者的4篇，通讯作者的1篇，不重复计算），均为第一资助。