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NIR-Driven Moist Upper Atmospheres of Synchronously Rotating Temperate Terrestrial ExoplanetsH2O is a key molecule in characterizing atmospheres of temperate terrestrial planets, and observations of transmission spectra are expected to play a primary role in detecting its signatures in the near future. The detectability of H2O absorption features in transmission spectra depends on the abundance of water vapor in the upper part of the atmosphere. We study the three-dimensional distribution of atmospheric H2O for synchronously rotating Earth-sized aquaplanets using the general circulation model (GCM) ROCKE-3D, and examine the effects of total incident flux and stellar spectral type. We observe a more gentle increase of the water vapor mixing ratio in response to increased incident flux than one-dimensional models suggest, in qualitative agreement with the climate-stabilizing effect of clouds around the substellar point previously observed in GCMs applied to synchronously rotating planets. However, the water vapor mixing ratio in the upper atmosphere starts to increase while the surface temperature is still moderate. This is explained by the circulation in the upper atmosphere being driven by the radiative heating due to absorption by water vapor and cloud particles, causing efficient vertical transport of water vapor. Consistently, the water vapor mixing ratio is found to be well-correlated with the near-infrared portion of the incident flux. We also simulate transmission spectra based on the GCM outputs, and show that for the more highly irradiated planets, the H2O signatures may be strengthened by a factor of a few, loosening the observational demands for a H2O detection.
Document ID
20170011274
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Fujii, Yuka
(Tokyo Inst. of Tech. Japan)
Del Genio, Anthony D.
(NASA Goddard Inst. for Space Studies New York, NY, United States)
Amundsen, David S.
(Columbia Univ. New York, NY, United States)
Date Acquired
November 27, 2017
Publication Date
October 17, 2017
Publication Information
Publication: Astrophysical Journal
Publisher: American Astronomical Society
Volume: 848
Issue: 2
ISSN: 0004-637X
e-ISSN: 1538-4357
Subject Category
Exobiology
Meteorology And Climatology
Report/Patent Number
GSFC-E-DAA-TN48818
Distribution Limits
Public
Copyright
Other

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