Study for the growth process of arctic PSC particles

在斯瓦尔巴群岛Ny-Ålesund，当平流层温度下降到冰的霜点附近时，激光雷达经常观测到（I型）极地平流层云（PSCs）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。PSCs在散射层和退极化层的温度历史的主要区别在于其结构被观察到的温度。在去极化极值处，散射比随时间的小幅增加表明固体颗粒的成核缓慢。包括温度历史在内的激光雷达观测表明，三明治结构是由两种不同类型的粒子的外部混合引起的。在低温下生长的大部分液体颗粒构成散射层，而在高温下，一小部分固体颗粒负责脱极化层。采用拉格朗日格式在粒子半径的径向空间中建立了模拟PSC粒子生长的新模型。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。该模型的性能在光化学模型内的PSC模拟和激光雷达数据的解释中被证实是有用的。

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.