Synonyms
Definition
Clouds are condensates (either liquid or solid) of gaseous atmospheric constituents, which play an important role in planetary atmospheres. Since clouds scatter and absorb incident stellar radiation as well as emergent thermal radiation and release latent heat during their formation, they control both the appearance and thermal structure of a planet. Furthermore, a cloud deck can both limit the depth an external observer can “see” into an atmosphere and thus hide molecular species, and it can alter a planet’s albedo. For such reasons, a basic understanding of the role clouds play is required to interpret exoplanet spectra or to obtain consistent temperature profiles and surface temperatures.
Overview
Clouds can form when the partial pressure of a chemical species exceeds its saturation vapor pressure. The initial distribution of cloud nuclei is formed by either homogenous or heterogeneous nucleation from the gas phase, where the first process needs...
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References and Further Reading
Ackerman A, Marley M (2001) Precipitating condensation clouds in substellar atmospheres. J Astrophys 556:872–884
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Helling C et al (2008) Comparative study of dust cloud modelling for substellar atmospheres. Mon Not R Astron Soc 391(4):1854–1873
Kaltenegger L, Jucks K, Traub W (2007) Spectral evolution of an Earth-like planet. Astrophys J 658:598
Kasting J (1991) CO2 condensation and the climate of early Mars. Icarus 94:1–13, ISSN 0019-1035
Kitzmann D et al (2010) Clouds in the atmospheres of extrasolar planets. I. Climatic effects of multi-layered clouds for Earth-like planets and implications for habitable zones. Astron Astrophys 511:A66
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Marley MS et al (2013) Clouds and hazes in exoplanet atmospheres. In: Mackwell S, Bullock M, Harder J (eds) Comparative climatology of terrestrial planets. University of Arizona Press, Tucson
Morley C et al (2013) Quantitatively assessing the role of clouds in the transmission spectrum of GJ 1214B. Astrophys J 775:A33
Pruppacher H, Klett J (1997) Microphysics of clouds and precipitation, 2nd edn. Kluwer, Dordrecht
Sing DK et al (2011) Hubble space telescope transmission spectroscopy of the exoplanet HD 189733b: high-altitude atmospheric haze in the optical and near-ultraviolet with STIS. Mon Not R Astron Soc 416:1443
Vasquez M et al (2013) Infrared radiative transfer in atmospheres of Earth-like planets around F, G, K, and M-type stars – II. Thermal emission spectra influenced by clouds. Astron Astrophys 557:A46
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© 2014 Springer-Verlag Berlin Heidelberg
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Marley, M.S., Kaltenegger, L., Kitzmann, D. (2014). Clouds. In: Amils, R., et al. Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-27833-4_306-3
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DOI: https://doi.org/10.1007/978-3-642-27833-4_306-3
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Publisher Name: Springer, Berlin, Heidelberg
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