Study for the growth process of arctic PSC particles

在斯瓦尔巴特群岛NY-Å地区，当平流层温度降至冰霜点附近时，激光雷达经常观测到(I类)极地平流层云(PSC)的垂直夹层结构，其中相对去极化层位于散射层的上方和下方。利用激光雷达观测和反向轨迹分析，研究了该结构的时间演化和温度历史。散射层和退偏振层中PSCs的温度历史的主要区别在于观察到结构的温度。在退极化极大值的高度，散射比随时间的小幅增加，意味着固体颗粒的缓慢成核。包括温度历史在内的这些激光雷达观测表明，夹层结构是由两种不同类型的粒子外部混合而成的。利用拉格朗日方法在粒子半径的径向空间建立了一种新的PSC粒子生长模型。该模型可以模拟外部混合的STS颗粒和NAT颗粒的生长和蒸发过程。该模型在光化学模型中的PSC模拟和激光雷达数据的解释中具有一定的实用价值。

A vertical sandwich structure of (type I) polar stratospheric clouds (PSCs), in which layers of relative depolarization are above and below a scattering layer, has frequently been observed by lidar at Ny-Ålesund, Svalbard when the stratospheric temnperature decreases to near the frost point of ice. Using lidar observations and backward trajectory analysis, we studied the time evolution of this structure and its temperature history. The main difference between the temperature history of PSCs in the scattering layer and those in the depolarization layer was the temperature at which the structure is observed. The small increase in the scattering ratio over time at the altitude of the depolarization maximum, implies a slow nucleation of solid particles. These lidar observations including temperature histories suggest that the sandwich structure arises from the external mixing of two different types of particles. A large fraction of liquid particles, grown at low temperature, constitutes the scattering layer, while at higher temperatures, a very small fraction of solid particles is responsible for the depolarization layer.A new model to simulate growth of PSC particles was constructed with using Lagrangean scheme in radial space of the particle radius. This model can simulate the growth and evaporation of externally mixed STS particles and NAT particles. The performance of the model was confirmed to be useful in PSC simulation within the photochemical model and interpretation of lidar data.