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

极涡内HNO_3、O_3、ClONO_2等痕量气体的分布受极地平流层云(PSCS)的影响。NAT(三水硝酸)颗粒是PSC颗粒的一种，它可以长大到足够大的尺寸，导致颗粒的沉淀，从而重新分配NOY。由于氯的失活速度减慢，反硝化气团中的臭氧损失持续时间更长。需要在一个模型中理解和考虑这些过程，以便尽可能准确地模拟重要痕量气体的分布。尤其是NAT粒子的成核和长大是一个关键点，因为这些过程在基于观测的模型中被参数化，但还没有完全被理解。即使是改进的参数化也会导致模拟结果与某些点的观测结果(如NAT的大小分布、NOY重分布)有所不同。机载红外测深仪CRIMSTA-NF(大气低温红外光谱仪和望远镜-新前沿)的测量将用于更深入地了解相关过程。CRIMSTA-NF测量中红外波段大气痕量气体热排放的海拔分布。这些测量可以得出几种痕量气体(如HNO_3、CFC-11、O_3、ClONO_2)的体积混合比(VMR)的二维截面，此外，还可以检测和区分不同的PSC(NAT、STS(过冷三元溶液)和ICE)。微小的NAT粒子(半径3微米)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，并且移动的大小取决于颗粒的尺寸分布。现有的检测方法没有考虑这种转变，该方法将进行更新，以减少误解。此外，新方法将能够推导出关于小NAT颗粒的颗粒尺寸分布的信息。此外，在反演过程中将考虑PSC的辐射影响，以显著改进存在PSC的情况下痕量气体VMRS的推导。该项目将使用化学和输运模型CLAMS(平流层化学拉格朗日模型)的模拟。CRIMSTA-NF观测和模拟结果之间的比较将被用来更详细地研究重要的过程。通过详细的比较，可以分析不同的方面，例如可能的温度偏差或温度波动对NAT成核的影响，模型分辨率(时间和空间)的影响，特别是NAT和STS粒子的成核和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.