Observing the two- and three- dimensional distributions of trace gases with the Heidelberger Airborne Imaging DOAS Instrument (HAIDI) on board HALO during the phase II mission EMerGe

该项目的重点是应用一种新的遥感2D和3D成像DOAS仪器HAIDI来调查欧洲和亚洲主要城市污染中心（MPC）（特大城市）排放的羽流的化学成分。这些活动将是德国研究飞机HALO的EMerGe任务的一部分，目前正在调查另外一个参与CAFE任务的活动。HAIDI的机载观测允许测量这些MPC流出羽流特征的关键参数，包括NO2、HCHO、SO2、CHOCHO、BrO、IO、OClO、H2O、O4和O3的微量气体分布以及气溶胶光学特性。由此产生的二维地图分辨率超过100米，宽度约为10公里，因此可以一次覆盖大面积。利用层析成像技术，可以检索包含垂直分布信息的3D地图。HAIDI观察了一些最相关的气体，以研究流出物中MPC羽流的化学成分和转化。我们将研究这些羽流的大小、分布和空间变化与地形和气象的关系。特别是作为关键成分的NO2的排放、转化和损失将被研究。结合在HALO上进一步观测到的组分，微量气体和气溶胶成分的化学变化对回答MPC排放羽流的局部、区域和全球影响问题具有重要意义。HAIDI还可以得出气溶胶光学特性，这将与HALO上气溶胶特性的现场测量相结合，以量化这些MPC羽流对大气辐射收支的影响。此外，导出的痕量气体分布是验证和改进EMerGe项目中模型数据的关键量。设想进一步验证卫星数据。通过HAIDI，将首次部署具有3D功能的系统，可以获得完整的3D痕量气体（和气溶胶光学特性）分布。为此，HAIDI使用了三个指向不同方向的成像DOAS仪器。在这个项目中，我们将基于我们以前的工作，开发算法，将这些数据集与层析成像方法结合在辐射传输模型中。由于这是HAIDI第一次在HALO上运行，因此必须在该项目中进行认证和适应过程。

The focus of this project is on the application of a new remote sensing 2D and 3D imaging DOAS instrument HAIDI to investigate the chemical composition of plumes emitted from major urban pollution centers (MPC) (megacities) in Europe and Asia. The activities will be part of the EMerGe mission for the German research airplane HALO, with an additional participation in the CAFE mission being currently under investigation. Airborne observations by HAIDI allow for measurements of key parameters for the characterization of these MPC outflow plumes, including trace gas distributions of NO2, HCHO, SO2, CHOCHO, BrO, IO, OClO, H2O, O4 and O3 as well as aerosol optical properties. The resulting 2D maps have a resolution better than 100 m with a width of ~10 km and thus cover large areas at once. Using tomographic techniques, 3D maps including information on the vertical distribution can be retrieved. HAIDI observes some of the most relevant gases to study the chemical composition and transformation of the MPC plumes in the outflow. We will study the size, distribution and spatial change of these plumes in dependence of topography and meteorology. Especially emission, transformation, and loss of NO2 as a key component will be investigated. In combination with further observed components on HALO, the chemical change of the trace gases and aerosol composition is of main interest to answer questions of the local, regional, and global influence of MPC emission plumes. HAIDI can also derive aerosol optical properties, which will be used in combination with in-situ measurements of aerosol characteristics on HALO to quantify the effect of these MPC plumes on the atmospheric radiation budget. Furthermore, the derived trace gas distributions are key quantities for the validation and improvement of model data within the EMerGe project. A further validation of satellite data is envisaged. With HAIDI, a system with 3D capability, allowing to derive full 3D trace gas (and aerosol optical property) distributions, will be deployed for the first time. For this purpose, HAIDI uses three imaging DOAS instruments pointing at different directions. In this project we will - based on our previous work - develop algorithms to combine these dataset in a radiative transfer model with tomographic approaches. Since this is the first time HAIDI operates on HALO, it has to undergo the certification and adaptation process within this project.