基于无人机平台的黑碳颗粒物垂直分布及环境效应评估

The vertical profiles of the concentration and mixing state of atmospheric black carbon (BC) determine its environment and climate effects. BC in high altitude may influence the evolution of planetary boundary layer, and have much higher efficiency in global warming than BC near surface. Till now, only a few airborne measurements of vertical profile of BC mixing state have been conducted with aircraft platform around the world, hindering the precise evaluation of the climate and environment impacts of BC. We plan to develop an unmanned aerial vehicle-based platform and a “semi-online” technique for the vertical observation of physical-chemical properties of BC. Combining online and “semi-online” techniques, vertical profiles of concentration, mixing state and chemical composition of BC-containing particles can be observed with the platform with low cost and in a long period. Based on the new platform, we plan to conduct vertical measurements in a background station in the North China Plain, focusing on the variation of mixing state and chemical composition profiles of BC-containing aerosol during the evolution of planetary boundary layer. Based on the dataset, we will also evaluate regional BC direct radiative forcing and boundary layer feedback, and analyze the contributions of different emission source types on those effects.

大气黑碳颗粒物浓度和混合态的垂直分布是影响黑碳环境气候效应的重要因素。高空分布的黑碳一方面可以改变边界层结构加剧雾霾污染，另一方面其气候增温效应与近地面黑碳相比有跨量级的增强。由于基于飞机平台的黑碳垂直分布观测资料相对有限，目前在很多地区均难以对其环境气候效应进行全面评估，这也是造成黑碳污染与气候效应评估存在巨大不确定性的重要原因之一。本项目拟建立基于无人机的黑碳理化特性飞行观测平台和“准在线”观测技术，通过将“在线”和“准在线”观测手段相结合，克服无人机载荷等方面的限制，实现无人机航域内黑碳混合态和化学成分垂直分布的低成本、长时期、高时间分辨率观测。基于搭建的飞行观测平台，在华北地区开展黑碳浓度和混合态垂直观测，分析不同季节、污染情景下，边界层演化过程中各关键高度上黑碳混合态和化学成分的变化特征，并基于观测数据利用模式评估黑碳的边界层反馈效应和直接辐射强迫。

针对大气边界层内（地面至约1km高度范围）气溶胶复杂理化特性垂直分布难以观测的问题，本项目自主研发了一种适用于无人机和系留汽艇平台的气溶胶自动采样系统，并建立了相应的“准在线”观测方法。新采样系统以气溶胶状态采集和存储样本，通过一系列技术手段最大程度地降低气溶胶在采集过程中的损失，采集的样本可供当前大部分主流气溶胶在线分析仪器检测，结合无人机/系留汽艇平台和地面在线观测仪器，可以实现近地面气溶胶混合态、密度、化学组分、吸湿性、挥发性等复杂理化特性垂直分布观测，扩展了气溶胶观测的手段和维度。利用系留汽艇搭载新研发的系统，在青藏高原三个典型城市开展了系列外场观测，获得了边界层演化过程中黑碳质量浓度、谱分布、混合态、以及气溶胶化学组分和吸湿性的垂直廓线数据库，揭示了青藏高原地区边界层内外黑碳气溶胶混合态垂直分布日变化特征、梯度差异和影响因素。