TY - JOUR
T1 - The circulation pattern and day-night heat transport in the atmosphere of a synchronously rotating aquaplanet
T2 - Dependence on planetary rotation rate
AU - Noda, S.
AU - Ishiwatari, M.
AU - Nakajima, K.
AU - Takahashi, Y. O.
AU - Takehiro, S.
AU - Onishi, M.
AU - Hashimoto, G. L.
AU - Kuramoto, K.
AU - Hayashi, Y. Y.
N1 - Funding Information:
Two anonymous reviewers are sincerely acknowledged for carefully reading the original manuscript and providing many helpful comments. This study was supported by MEXT KAKENHI Grant Number JP23103003 of Ministry of Education, Culture, Sports, Science and Technology, Japan, and JSPS KAKENHI Grant Numbers JP20540223, JP24340016, JP25400219, JP25800264 and global COE program “Foundation of International Center for Planetary Science” of the Japan Society for the Promotion of Science. A part of calculations were performed by the SX8R of the Institute of Space and Astronautical Science supercomputer system, Japan Aerospace Exploration Agency. Resolution tests of numerical integrations used the SX series of Center for Global Environmental Research, National Institute of Environmental Studies, Japan. We used the software developed by Dennou Ruby Project ( http://www.gfd-dennou.org/library/ruby/ ) for simulations, analyses, and drawings.
Publisher Copyright:
© 2016 The Authors
PY - 2017/1/15
Y1 - 2017/1/15
N2 - In order to investigate a possible variety of atmospheric states realized on a synchronously rotating aquaplanet, an experiment studying the impact of planetary rotation rate is performed using an atmospheric general circulation model (GCM) with simplified hydrological and radiative processes. The entire planetary surface is covered with a swamp ocean. The value of planetary rotation rate is varied from zero to the Earth's, while other parameters such as planetary radius, mean molecular weight and total mass of atmospheric dry components, and solar constant are set to the present Earth's values. The integration results show that the atmosphere reaches statistically equilibrium states for all runs; none of the calculated cases exemplifies the runaway greenhouse state. The circulation patterns obtained are classified into four types: Type-I characterized by the dominance of a day-night thermally direct circulation, Type-II characterized by a zonal wave number one resonant Rossby wave over a meridionally broad westerly jet on the equator, Type-III characterized by a long time scale north-south asymmetric variation, and Type-IV characterized by a pair of mid-latitude westerly jets. With the increase of planetary rotation rate, the circulation evolves from Type-I to Type-II and then to Type-III gradually and smoothly, whereas the change from Type-III to Type-IV is abrupt and discontinuous. Over a finite range of planetary rotation rate, both Types-III and -IV emerge as statistically steady states, constituting multiple equilibria. In spite of the substantial changes in circulation, the net energy transport from the day side to the night side remains almost insensitive to planetary rotation rate, although the partition into dry static energy and latent heat energy transports changes. The reason for this notable insensitivity is that the outgoing longwave radiation over the broad area of the day side is constrained by the radiation limit of a moist atmosphere, so that the transport to the night side, which is determined as the difference between the incoming solar radiation and the radiation limit, cannot change greatly.
AB - In order to investigate a possible variety of atmospheric states realized on a synchronously rotating aquaplanet, an experiment studying the impact of planetary rotation rate is performed using an atmospheric general circulation model (GCM) with simplified hydrological and radiative processes. The entire planetary surface is covered with a swamp ocean. The value of planetary rotation rate is varied from zero to the Earth's, while other parameters such as planetary radius, mean molecular weight and total mass of atmospheric dry components, and solar constant are set to the present Earth's values. The integration results show that the atmosphere reaches statistically equilibrium states for all runs; none of the calculated cases exemplifies the runaway greenhouse state. The circulation patterns obtained are classified into four types: Type-I characterized by the dominance of a day-night thermally direct circulation, Type-II characterized by a zonal wave number one resonant Rossby wave over a meridionally broad westerly jet on the equator, Type-III characterized by a long time scale north-south asymmetric variation, and Type-IV characterized by a pair of mid-latitude westerly jets. With the increase of planetary rotation rate, the circulation evolves from Type-I to Type-II and then to Type-III gradually and smoothly, whereas the change from Type-III to Type-IV is abrupt and discontinuous. Over a finite range of planetary rotation rate, both Types-III and -IV emerge as statistically steady states, constituting multiple equilibria. In spite of the substantial changes in circulation, the net energy transport from the day side to the night side remains almost insensitive to planetary rotation rate, although the partition into dry static energy and latent heat energy transports changes. The reason for this notable insensitivity is that the outgoing longwave radiation over the broad area of the day side is constrained by the radiation limit of a moist atmosphere, so that the transport to the night side, which is determined as the difference between the incoming solar radiation and the radiation limit, cannot change greatly.
KW - Astrobiology
KW - Atmospheres structure
KW - Atmospheres, dynamics
KW - Extra-solar, planets
KW - Meteorology
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U2 - 10.1016/j.icarus.2016.09.004
DO - 10.1016/j.icarus.2016.09.004
M3 - Article
AN - SCOPUS:84994634440
SN - 0019-1035
VL - 282
SP - 1
EP - 18
JO - Icarus
JF - Icarus
ER -