Hazy Blue Worlds: A Holistic Aerosol Model for Uranus and Neptune, Including Dark Spots.
Hazy Blue Worlds: A Holistic Aerosol Model for Uranus and Neptune, Including Dark Spots.
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DOI：
10.1029/2022je007189
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发表时间：
2022-06
影响因子：
4.8
通讯作者：
Dobinson, J.
中科院分区：
文献类型：
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作者：
Irwin, P. G. J.;Teanby, N. A.;Fletcher, L. N.;Toledo, D.;Orton, G. S.;Wong, M. H.;Roman, M. T.;Perez-Hoyos, S.;James, A.;Dobinson, J.
我们给出了几台仪器对天王星和海王星的可见光/近红外(0.3-2.5千μ米)观测的再分析(使用明纳尔特临边暗化近似)。我们发现了一个垂直气溶胶分布的共同模式，即与观测到的两个行星的反射率光谱相一致，包括：(A)一个基本气压为>；5-7巴的深气溶胶层，假定由硫化氢冰和光化学霾的混合物组成；(B)一层光化学霾/冰，与1-2巴甲烷凝结水平上的高静态稳定层重合；以及(C)一层延伸的光化学烟雾，很可能与1-2bar层的成分基本相同，从这一层一直延伸到被认为产生光化学烟雾粒子的平流层。对于海王星，我们发现我们还需要在∼0.2bar添加一层微米大小的甲烷冰粒，以解释在更长的甲烷吸收波长上反射增强的原因。我们认为，甲烷凝聚到1-2巴气溶胶层底部的雾霾粒子上，形成了冰/雾霾粒子，这些粒子非常迅速地增长到大尺寸，并立即“下雪”(正如Carlson等人预测的那样)。(1988年)，https://doi.org/10.1175/1520-0469(1988)045<；2066:CMOTGP>；2.0.CO；2)，在更深的层次重新蒸发，释放其核心雾霾粒子，作为硫化氢冰形成的凝结核。此外，我们发现“暗斑”的光谱特征，如旅行者2号/国际空间站大暗斑和HST/WFC3 NDS-2018，很好地模拟了只有深层气溶胶层变暗或可能清除的情况。由甲烷冷凝引起的由三到四个不同层组成的单个气溶胶模式很好地模拟了0.3到2.5亿μm的冰巨型反射率光谱，这似乎导致了雾霾和种子CH4雪在其底部堆积，最深的硫化氢/霾层变暗，这被发现很好地解释了暗斑的光谱特性。
We present a reanalysis (using the Minnaert limb‐darkening approximation) of visible/near‐infrared (0.3–2.5 μm) observations of Uranus and Neptune made by several instruments. We find a common model of the vertical aerosol distribution i.e., consistent with the observed reflectivity spectra of both planets, consisting of: (a) a deep aerosol layer with a base pressure >5–7 bar, assumed to be composed of a mixture of H2S ice and photochemical haze; (b) a layer of photochemical haze/ice, coincident with a layer of high static stability at the methane condensation level at 1–2 bar; and (c) an extended layer of photochemical haze, likely mostly of the same composition as the 1–2‐bar layer, extending from this level up through to the stratosphere, where the photochemical haze particles are thought to be produced. For Neptune, we find that we also need to add a thin layer of micron‐sized methane ice particles at ∼0.2 bar to explain the enhanced reflection at longer methane‐absorbing wavelengths. We suggest that methane condensing onto the haze particles at the base of the 1–2‐bar aerosol layer forms ice/haze particles that grow very quickly to large size and immediately “snow out” (as predicted by Carlson et al. (1988), https://doi.org/10.1175/1520-0469(1988)045<2066:CMOTGP>2.0.CO;2), re‐evaporating at deeper levels to release their core haze particles to act as condensation nuclei for H2S ice formation. In addition, we find that the spectral characteristics of “dark spots”, such as the Voyager‐2/ISS Great Dark Spot and the HST/WFC3 NDS‐2018, are well modelled by a darkening or possibly clearing of the deep aerosol layer only. Ice Giant reflectivity spectra from 0.3 to 2.5 μm well approximated by a single aerosol model comprised of three to four distinct layers Static stability region at 1–2 bar, caused by methane condensation, seems to lead to build‐up of haze and seeds CH4 snow at its base Darkening of deepest H2S/haze layer, based at p > 5–7 bar, found to account well for spectral properties of dark spots