Variability of Water and Oxygen Absorption Bands in the Disk-Integrated Spectra of the Earth
Variability of Water and Oxygen Absorption Bands in the Disk-Integrated Spectra of the Earth
复制标题
地球圆盘积分光谱中水和氧吸收带的变化
DOI：
10.1088/0004-637x/765/2/76
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
藤井 友香
中科院分区：
文献类型：
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作者：
増田啓介;栗原進;藤井 友香
我们研究的主要大气吸收功能的变化，在磁盘集成的地球光谱与未来的应用，地球类似物铭记，集中在昼夜时间尺度。我们首先分析了EPOXI使命提供的地球观测数据，发现H2 O和O2波段的吸收深度变化率为5%-20%，这两种分子在观测范围内具有主要特征。通过与地球观测卫星云图资料的相关分析，发现它们的变化模式主要是由于云量分布不均匀造成的。为了定量地解释观测到的变化，我们考虑一个简单的不透明云模型，该模型假设云层完全阻挡云层以下大气的光谱影响，相当于假设入射光在云顶水平完全散射。该模型是相当成功的，并再现EPOXI数据从像素级EOS云/水汽数据。H2O和O2波段日变化的差异归因于这些分子物种在大气中的垂直和水平分布的不同。在地球上，大气水蒸气的不均匀分布是由于它与地球表面的液相和固相H2O交换的时间尺度比大气混合时间短。如果在地球类似物的光谱中检测到这种变化模式的差异，它将提供关于其大气层不均匀成分的信息。
We study the variability of major atmospheric absorption features in the disk-integrated spectra of Earth with future application to Earth-analogs in mind, concentrating on the diurnal timescale. We first analyze observations of Earth provided by the EPOXI mission, and find 5%–20% fractional variation of the absorption depths of H 2 O and O 2 bands, two molecules that have major signatures in the observed range. From a correlation analysis with the cloud map data from the Earth Observing Satellite (EOS), we find that their variation pattern is primarily due to the uneven cloud cover distribution. In order to account for the observed variation quantitatively, we consider a simple opaque cloud model, which assumes that the clouds totally block the spectral influence of the atmosphere below the cloud layer, equivalent to assuming that the incident light is completely scattered at the cloud top level. The model is reasonably successful, and reproduces the EPOXI data from the pixel-level EOS cloud/water vapor data. A difference in the diurnal variability patterns of H 2 O and O 2 bands is ascribed to the differing vertical and horizontal distribution of those molecular species in the atmosphere. On Earth, the inhomogeneous distribution of atmospheric water vapor is due to the existence of its exchange with liquid and solid phases of H 2 O on the planet's surface on a timescale short compared with atmospheric mixing times. If such differences in variability patterns were detected in spectra of Earth-analogs, it would provide the information on the inhomogeneous composition of their atmospheres.