CRISTA-NF observations of polar stratospheric clouds and trace gas volume mixing ratios in the Arctic winter stratosphere

极地平流层云（PSCs）对极地涡旋内部HNO3、O3、ClONO2等多种微量气体的分布有重要影响。NAT（硝酸三水合物）颗粒是PSC颗粒的一种，它可以生长到足够大的尺寸，从而引起颗粒的沉积，从而引起NOy的重新分配。反硝化气团中的臭氧损失持续时间更长，因为氯的失活减慢了。这些过程需要在一个模型中被理解和考虑，以尽可能精确地模拟重要微量气体的分布。特别是NAT颗粒的成核和生长是一个关键点，因为这些过程在基于观测的模型中被参数化，但尚未完全理解。即使改进的参数化也会导致模拟结果在某些点上与观测结果不同（例如NAT的大小分布，NOy再分布）。航空红外翼缘探测仪CRISTA-NF（低温红外光谱仪和大气望远镜-新前沿）的测量结果将用于更深入地了解相关过程。CRISTA-NF测量中红外大气微量气体热排放的高度分布。这些测量可以得到几种微量气体（如HNO3、CFC-11、O3、ClONO2）的体积混合比（VMRs）的二维截面，此外，还可以检测和区分不同的PSCs （NAT、STS（过冷三元溶液）和冰）。NAT小颗粒（半径为> 3µm）会产生光谱特征，用于检测。新的发现表明，这一特征是可以移动的，移动的幅度取决于颗粒的大小分布。现有的检测方法没有考虑到这种变化，将对方法进行更新以减少误解。此外，新方法将使有关NAT小颗粒粒径分布的信息的推导成为可能。此外，将在检索过程中考虑PSCs对辐射度的影响，以显着改善PSCs存在下痕量气体vmr的推导。该项目将使用化学和输运模式CLaMS（平流层化学拉格朗日模式）进行模拟。CRISTA-NF观测结果与模拟结果之间的比较将用于更详细地研究重要过程。详细的比较可以分析不同方面，例如可能的温度偏差或温度波动对NAT成核的影响，模式分辨率（时间和空间）的影响，特别是NAT和STS颗粒同时成核和HNO3的吸收，包括对尺寸分布和NOy再分布的影响。

The distributions of many trace gases such as HNO3, O3, and ClONO2 inside the polar vortex are influenced by polar stratospheric clouds (PSCs). NAT (Nitric Acid Trihydrate) particles, which are one type of PSC particles, can grow to sizes, which are large enough to cause a sedimentation of the particles and, thus, a redistribution of NOy. The ozone loss in denitrified air masses lasts longer, since the deactivation of chlorine is slowed down. These processes need to be understood and considered in a model to simulate the distribution of the important trace gases as precisely as possible. Especially the nucleation and growth of NAT particles is a key point, since these processes are parametrized in models based on observations but not yet understood completely. Even improved parametrizations lead to simulation results that still differ from observations at some points (e.g. size distribution of NAT, NOy redistribution).Measurements by the airborne infrared limb sounder CRISTA-NF (CRyogenic Infrared Spectrometers and Telescope for the Atmosphere - New Frontiers) will be used to gain more insight into the relevant processes. CRISTA-NF measures altitude profiles of thermal emissions of atmospheric trace gases in the mid-infrared. These measurements allow the derivation of 2-dimensional cross-sections of volume mixing ratios (VMRs) of several trace gases (e.g. HNO3, CFC-11, O3, ClONO2) and, additionally, the detection and discrimination of different PSCs (NAT, STS (Supercooled Ternary Solution), and ice). Small NAT particles (radii > 3 µm) cause a spectral feature, which is used for detection. New findings show that this feature can be shifted and the magnitude of the shift depends on the size distribution of the particles. The existing detection method does not consider this shift and the method will be updated to reduce misinterpretations. Additionally, the new method will enable the derivation of information about the particle size distribution of small NAT particles. Furthermore, the radiance influence due to PSCs will be considered in the retrieval process to significantly improve the derivation of trace gas VMRs in the presence of PSCs.Simulations by the chemistry and transport model CLaMS (Chemical Lagrangian Model of the Stratosphere) will be used in the project. Comparisons between the CRISTA-NF observations and simulation results will be used to study the important processes in more detail. Detailed comparisons enable the analysis of different aspects such as the influence of a possible temperature bias or temperature fluctuations on the nucleation of NAT, the influence of model resolution (temporal and spatial), and especially the nucleation of and the HNO3 uptake by NAT and STS particles at the same time including the consequences for size distributions and NOy redistribution.