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Title: NIR-driven Moist Upper Atmospheres of Synchronously Rotating Temperate Terrestrial Exoplanets

Abstract

H{sub 2}O 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 H{sub 2}O 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 H{sub 2}O 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-infraredmore » 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 H{sub 2}O signatures may be strengthened by a factor of a few, loosening the observational demands for a H{sub 2}O detection.« less

Authors:
; ;  [1]
  1. NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY (United States)
Publication Date:
OSTI Identifier:
22679756
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 848; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ABUNDANCE; DETECTION; GENERAL CIRCULATION MODELS; IRRADIATION; MIXING RATIO; MOLECULES; NEAR INFRARED RADIATION; ONE-DIMENSIONAL CALCULATIONS; PLANETS; SATELLITE ATMOSPHERES; SATELLITES; SPECTRA; SURFACES; THREE-DIMENSIONAL CALCULATIONS; WATER; WATER VAPOR

Citation Formats

Fujii, Yuka, Del Genio, Anthony D., and Amundsen, David S.. NIR-driven Moist Upper Atmospheres of Synchronously Rotating Temperate Terrestrial Exoplanets. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA8955.
Fujii, Yuka, Del Genio, Anthony D., & Amundsen, David S.. NIR-driven Moist Upper Atmospheres of Synchronously Rotating Temperate Terrestrial Exoplanets. United States. doi:10.3847/1538-4357/AA8955.
Fujii, Yuka, Del Genio, Anthony D., and Amundsen, David S.. Fri . "NIR-driven Moist Upper Atmospheres of Synchronously Rotating Temperate Terrestrial Exoplanets". United States. doi:10.3847/1538-4357/AA8955.
@article{osti_22679756,
title = {NIR-driven Moist Upper Atmospheres of Synchronously Rotating Temperate Terrestrial Exoplanets},
author = {Fujii, Yuka and Del Genio, Anthony D. and Amundsen, David S.},
abstractNote = {H{sub 2}O 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 H{sub 2}O 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 H{sub 2}O 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 H{sub 2}O signatures may be strengthened by a factor of a few, loosening the observational demands for a H{sub 2}O detection.},
doi = {10.3847/1538-4357/AA8955},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 848,
place = {United States},
year = {2017},
month = {10}
}