2009年7月NIR Keck AO观测中海王星纬向风速的色散
Dispersion in Neptune's Zonal Wind Velocities from NIR Keck AO Observations in July 2009
摘要：
我们报告了2009年7月14日和16日从10-m W.M.在H-（1.4-1.8 μm）和K '-（2.0-2.4 μm）波段对海王星的观测结果。凯克II望远镜使用耦合到自适应光学（AO）系统的近红外相机NIRC 2。我们在几个小时内跟踪54个明亮的大气特征的位置，以获得它们的纬向和纬向速度，并进行辐射转移建模，以测量在两个波段同时看到的50个特征的云顶压力。我们在7月14日观察到一个南极特征（SPF），7月16日在~65 ° S观察到三个SPF。在这两个夜晚观察到的SPF是不同的特征，与海王星风暴的高变化性一致。Sromovsky等人的平滑旅行者风廓线拟合在海王星的纬向风速上存在显著的分散性，Icarus 105，140（1993），远大于我们从垂直风切变中所预期的上限，在赤道和南半球中纬度地区观测到最大的色散。特征压力与平滑的旅行者风廓线的纬向速度残差的比较也直接揭示了垂直风切变机制在引起纬向风弥散方面的主导作用。垂直风切变不是造成7月14日H波段和7月16日K '波段观测到的纬向速度频散和偏差差异的主要原因。在这些短时间内跟踪的特征的纬向速度的分散由一个或多个机制主导，而不是垂直风切变，这可能会导致分散的变化和纬向速度的偏差在几小时到几天的时间尺度上。
英文摘要：
We report observations of Neptune made in H-(1.4-1.8 μm) and K'-(2.0-2.4 μm) bands on 14 and 16 July 2009 from the 10-m W.M. Keck II Telescope using the near-infrared camera NIRC2 coupled to the Adaptive Optics (AO) system. We track the positions of 54 bright atmospheric features over a few hours to derive their zonal and latitudinal velocities, and perform radiative transfer modeling to measure the cloud-top pressures of 50 features seen simultaneously in both bands. We observe one South Polar Feature (SPF) on 14 July and three SPFs on 16 July at ~65 deg S. The SPFs observed on both nights are different features, consistent with the high variability of Neptune's storms. There is significant dispersion in Neptune's zonal wind velocities about the smooth Voyager wind profile fit of Sromovsky et al., Icarus 105, 140 (1993), much greater than the upper limit we expect from vertical wind shear, with the largest dispersion seen at equatorial and southern mid-latitudes. Comparison of feature pressures vs. residuals in zonal velocity from the smooth Voyager wind profile also directly reveals the dominance of mechanisms over vertical wind shear in causing dispersion in the zonal winds. Vertical wind shear is not the primary cause of the difference in dispersion and deviation in zonal velocities between features tracked in H-band on 14 July and those tracked in K'-band on 16 July. Dispersion in the zonal velocities of features tracked over these short time periods is dominated by one or more mechanisms, other than vertical wind shear, that can cause changes in the dispersion and deviation in the zonal velocities on timescales of hours to days.
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