arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2010.02589astro-ph.EP
收藏

地球作为一个系外行星:一。使用空间分辨的MODIS数据的时变热发射

Earth as an Exoplanet: I. Time variable thermal emission using spatially resolved MODIS data

Jean-Noël Mettler, Sascha P. Quanz, Ravit Helled

摘要:

就目前而言,地球仍然是一个可居住(和有人居住)的世界的最好和唯一的例子。因此,必须探索和了解地球的各种光谱特征和变化,以便为未来仪器和飞行任务的设计提供信息,并了解其诊断能力以及潜在的局限性。在这项工作中,我们使用的地球观测数据收集的中分辨率成像分光光度计仪器搭载的水卫星。完整的数据集包括对地球上五个不同地点(亚马逊雨林、南极洲、北极、印度洋和撒哈拉沙漠)在3.66-14.40微米范围内进行的15年热辐射观测。然后,我们确定通量水平和变化作为波长和表面类型(即气候带和表面热特性)的函数,并调查是否可以检测到指示地球倾斜旋转轴的周期性信号。我们的研究结果表明:(1)当分析热辐射数据时,观测几何学起着重要的作用,因为地球的光谱变化取决于下面的主要表面类型,变化系数为3或更多;(2)来自二氧化碳的典型强吸收带(15微米)和臭氧(9.65微米)在极地地区的数据中明显不太明显,部分缺失,这意味着估计这些分子的正确丰度水平可能具有挑战性在这些情况下;(3)时间分辨热发射光谱编码了有关季节/行星活动的信息,但其意义取决于观测几何和所考虑的光谱带

英文摘要:

For the time being, Earth remains the best and only example of a habitable (and inhabited) world. Therefore, it is important to explore and understand the full range of spectral signatures and variability of Earth in order to inform the design of future instruments and missions, and understand their diagnostic power as well as potential limitations. In this work we use Earth observation data collected by the MODIS instrument aboard the Aqua satellite. The complete data set comprises 15 years of thermal emission observations in the 3.66-14.40 microns range for five different locations on Earth (Amazon Rainforest, Antarctica, Arctic, Indian Ocean and the Sahara Desert). We then determine flux levels and variations as a function of wavelength and surface type (i.e. climate zone and surface thermal properties) and investigate whether periodic signals indicating Earth's tilted rotation axis can be detected. Our findings suggest that (1) viewing geometry plays an important role when thermal emission data is analyzed as Earth's spectrum varies by a factor of three and more depending on the dominant surface type underneath; (2) typically strong absorption bands from carbon dioxide (15 microns) and ozone (9.65 microns) are significantly less pronounced and partially absent in data from the polar regions implying that estimating correct abundance levels for these molecules might be challenging in these cases; (3) the time-resolved thermal emission spectrum encodes information about seasons/planetary obliquity, but the significance depends on the viewing geometry and spectral band considered

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑