Earth as an Exoplanet. II. Earth’s Time-variable Thermal Emission and Its Atmospheric Seasonality of Bioindicators ...

• Main Authors: Mettler, Jean-Noël, Quanz, Sascha Patrick, Helled, Ravit, Olson, Stephanie L., Schwieterman, Edward W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: ETH Zurich 2023
• Subjects: South pole
• Online Access: https://dx.doi.org/10.3929/ethz-b-000608053; http://hdl.handle.net/20.500.11850/608053

We assess the dependence of Earth’s disk-integrated mid-infrared thermal emission spectrum on observation geometries and investigate which and how spectral features are impacted by seasonality on Earth. We compiled an exclusive data set containing 2690 disk-integrated thermal emission spectra for four different full-disk observing geometries (North and South Pole-centered and Africa and Pacific-centered equatorial views) over four consecutive years. The spectra were derived from 2378 spectral channels in the wavelength range from 3.75-15.4 μm (nominal resolution ≈1200) and were recorded by the Atmospheric Infrared Sounder on board the Aqua satellite. We learned that there is significant seasonal variability in Earth’s thermal emission spectrum, and the strength of spectral features of bioindicators, such as N2O, CH4, O3, and CO2 depends strongly on both season and viewing geometry. In addition, we found a strong spectral degeneracy with respect to the latter two indicating that multi-epoch measurements and ... : The Astrophysical Journal, 946 (2) ...