Three‐dimensional modeling of the trajectories of visible noctilucent cloud particles: An indication of particle nucleation well below the mesopause
Three‐dimensional modeling of the trajectories of visible noctilucent cloud particles: An indication of particle nucleation well below the mesopause
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DOI：
10.1029/2006jd008106
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发表时间：
2007-08
影响因子：
--
通讯作者：
U. Berger;U. Zahn
中科院分区：
文献类型：
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作者：
U. Berger;U. Zahn
[1]夜光云（NLC）形成于夏季高纬度地区，高度接近83公里。在50°至65°的纬度范围内可以观察到最佳的视觉效果。云粒子很可能是由高层大气风从它们的出生地（成核地点）到观测地点的相当长的距离上输送的，然后再到它们再次升华的温暖地区。在这里，我们使用一个三维拉格朗日冰传输模型来识别NLC粒子的成核位置，这些粒子在纬度69°N以上垂直观察到（例如，由ALOMAR天文台的地面激光雷达观测）。我们将研究限制在被观察时半径大于50 nm或20 nm的颗粒。我们发现这些粒子的成核平均只比在69°N观测到的高出3 km。后一种说法意味着NLC粒子的成核平均发生在当地中层顶以下的一个尺度高度以上。此外，在69°N上空观测到的NLC粒子在观测地点以北纬度约9°处平均成核。它们在成核和到达观测点之间的传输时间与成核和观测点之间的纬度差明显正相关（在所观测粒子的半径和传输时间之间不存在类似的强相关性）。在69°N以上观察到的NLC颗粒的运输时间的中值为36小时。
[1] Noctilucent clouds (NLC) form in summer at high latitudes at altitudes close to 83 km. Visually they can be observed best in the latitude band 50° to 65°. The cloud particles are most likely transported by the upper atmosphere winds over substantial distances from their birth place (site of nucleation) to the site of their observation and subsequently to warmer regions where they sublimate again. Here we use a 3-D Lagrangian ice transport model to identify the nucleation sites of NLC particles which are observed vertically above a latitude of 69°N (e.g., by ground-based lidars at the ALOMAR observatory). We limit the study to particles which have radii larger than either 50 nm or 20 nm when being observed. We find that these particles were nucleated on average only 3 km higher than observed at 69°N. The latter statement implies that nucleation of NLC particles occurs on average more than a scale height below the local mesopause. Furthermore, NLC particles observed overhead at 69°N were nucleated on average about 9° in latitude north of the observation site. Their transport time between nucleation and reaching the observation site is clearly and positively correlated with the latitude difference between the nucleation and observation sites (a similar strong correlation does not exist between the radius and the transport time of the observed particle). The median value of transport times of NLC particles observed above 69°N is 36 hours.