Nucleation of mesospheric cloud particles: Sensitivities and limits
Nucleation of mesospheric cloud particles: Sensitivities and limits
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DOI：
10.1002/2015ja021764
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发表时间：
2016-03
期刊：
影响因子：
--
通讯作者：
H. Wilms;M. Rapp;A. Kirsch
中科院分区：
文献类型：
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作者：
H. Wilms;M. Rapp;A. Kirsch
中间层冰粒的成核被认为是通过流星烟雾粒子的非均质成核而发生的。然而，决定成核速率的几个因素知之甚少。为了研究成核率的不确定性对云特性的影响，我们使用了大气共同体气溶胶和辐射模式，并系统地改变了成核率超过±10个数量级。在一组模拟中，大气的背景状态由气候条件描述。在第二组中，使用来自Kühlungsborn机械环流模式（KMCM）的重力波扰动廓线，在中层顶处具有9 K（0.45 m/s）量级的典型温度（垂直风）扰动。由此产生的反射云（NLC）的特性进行比较，激光雷达和卫星测量。与激光雷达测量相比，现实的NLC只能在成核率与标准假设相比降低多达3个数量级时才能建模。对于相同的情况下，模拟的NLC比较最好的卫星测量，如果成核率降低了2个数量级或更多。中层顶的动力学过程强烈地影响着NLC的发展。在重力波扰动的大气中，冰粒只有有限的成核和生长时间。增长时间受垂直风的限制，因为垂直风决定了冰粒在过饱和区的停留时间。由于KMCM中的垂直风振幅达到1.5 m/s（与气候学中的平均上升流1.4 cm/s相比），因此在重力波扰动的大气中，冰粒仍然比气候背景条件下小得多。
Nucleation of mesospheric ice particles is thought to occur via heterogeneous nucleation on meteor smoke particles. However, several factors determining the nucleation rate are poorly known. To study the effect of uncertainties in the nucleation rate on cloud properties, we use the Community Aerosol and Radiation Model for Atmospheres and systematically vary the nucleation rate over ±10 orders of magnitude. In one set of simulations, the background state of the atmosphere is described by climatological conditions. In a second set, gravity wave‐perturbed profiles from the Kühlungsborn Mechanistic general Circulation Model (KMCM) are used with typical temperature (vertical wind) perturbations at the mesopause on the order of 9 K (0.45 m/s). The resulting noctilucent cloud (NLC) characteristics are compared to lidar and satellite measurements. Realistic NLCs compared to the lidar measurements can only be modeled if the nucleation rate is reduced by up to 3 orders of magnitude compared to standard assumptions. For the same cases, the simulated NLCs compare best to the satellite measurements if the nucleation rate is reduced by 2 orders of magnitude or more. Dynamical processes at the mesopause strongly influence the NLC development. In a gravity wave‐perturbed atmosphere, the ice particles have only limited time for nucleation and growth. The growth time is limited by the vertical wind, because the vertical wind determines the residence time of the ice particles in the supersaturated region. Since the vertical wind amplitudes reach 1.5 m/s in KMCM (compared to a mean upwelling of ∼4 cm/s in the climatology), the ice particles remain significantly smaller in a gravity wave‐perturbed atmosphere than in climatological background conditions.