Clouds in the atmospheres of extrasolar planets

Kitzmann, Daniel; Patzer, A. B. C.; Rauer, H.

doi:10.1051/0004-6361/201220025

Cited by 36 publications

(41 citation statements)

References 37 publications

(55 reference statements)

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“…It would be useful in future to compare them with more sophisticated schemes such as are currently used for Earth climate studies [e.g., Khairoutdinov and Randall, 2001]. In addition, it has been suggested recently that the two-stream approach to radiative transfer calculations (which we use) may be inaccurate for CO 2 cloud scattering [Kitzmann et al, 2013]. If this is the case, it would mean that our peak temperatures in Figure 11 are slightly overestimated.…”

Section: 1002/2015je004787mentioning

confidence: 99%

Comparison of “warm and wet” and “cold and icy” scenarios for early Mars in a 3‐D climate model

et al. 2015

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We use a 3-D general circulation model to compare the primitive Martian hydrological cycle in "warm and wet" and "cold and icy" scenarios. In the warm and wet scenario, an anomalously high solar flux or intense greenhouse warming artificially added to the climate model are required to maintain warm conditions and an ice-free northern ocean. Precipitation shows strong surface variations, with high rates around Hellas basin and west of Tharsis but low rates around Margaritifer Sinus (where the observed valley network drainage density is nonetheless high). In the cold and icy scenario, snow migration is a function of both obliquity and surface pressure, and limited episodic melting is possible through combinations of seasonal, volcanic, and impact forcing. At surface pressures above those required to avoid atmospheric collapse (∼0.5 bar) and moderate to high obliquity, snow is transported to the equatorial highland regions where the concentration of valley networks is highest. Snow accumulation in the Aeolis quadrangle is high, indicating an ice-free northern ocean is not required to supply water to Gale crater. At lower surface pressures and obliquities, both H 2 O and CO 2 are trapped as ice at the poles and the equatorial regions become extremely dry. The valley network distribution is positively correlated with snow accumulation produced by the cold and icy simulation at 41.8 ∘ obliquity but uncorrelated with precipitation produced by the warm and wet simulation. Because our simulations make specific predictions for precipitation patterns under different climate scenarios, they motivate future targeted geological studies. BackgroundDespite decades of research, deciphering the nature of Mars' early climate remains a huge challenge. Although Mars receives only 43% of the solar flux incident on Earth, and the Sun's luminosity was likely 20-30% lower 3-4 Ga, there is extensive evidence for aqueous alteration on Mars' late Noachian and early Hesperian terrain. This evidence includes dendritic valley networks (VNs) that are distributed widely across low to middle latitudes [Carr, 1996;Mangold et al., 2004;Hynek et al., 2010], open-basin lakes [Fassett and Head, 2008b], in situ observations of conglomerates [Williams et al., 2013], and spectroscopic observations of phyllosilicate and sulfate minerals [Bibring et al., 2006;Mustard et al., 2008;Ehlmann et al., 2011].All these features indicate a pervasive influence of liquid water on the early Martian surface. Nonetheless, key uncertainties in the nature of the early Martian surface environment remain. These include the intensity and duration of warming episodes and the extent to which the total surface H 2 O and CO 2 inventories were greater than today. Broadly speaking, proposed solutions to the problem can be divided into those that invoke long-term warm, wet conditions [e.g., Pollack et al., 1987;Craddock and Howard, 2002] and those that assume the planet was mainly frozen, with aquifer discharge or episodic / seasonal melting of snow and ice deposits provid...

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Section: 1002/2015je004787mentioning

confidence: 99%

Comparison of “warm and wet” and “cold and icy” scenarios for early Mars in a 3‐D climate model

et al. 2015

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“…On the other hand, the optical properties of particles with sizes larger than a few micrometers are essentially flat in the visible and near IR (e.g., Kitzmann et al, 2010). Compared to the cloud-free cases, this would lead to a constant offset in the planetary albedo, which is almost independent from the incident stellar radiation (see, e.g., Kitzmann et al, 2011 for H 2 O clouds andKitzmann et al, 2013 for CO 2 clouds).…”

Section: Ice-albedo Feedback and Atmospherementioning

confidence: 99%

The Dependence of the Ice-Albedo Feedback on Atmospheric Properties

et al. 2013

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Ice-albedo feedback is a potentially important destabilizing effect for the climate of terrestrial planets. It is based on the positive feedback between decreasing surface temperatures, an increase of snow and ice cover, and an associated increase in planetary albedo, which then further decreases surface temperature. A recent study shows that for M stars, the strength of the ice-albedo feedback is reduced due to the strong spectral dependence of stellar radiation and snow/ice albedos; that is, M stars primarily emit in the near IR, where the snow and ice albedo is low, and less in the visible, where the snow/ice albedo is high.This study investigates the influence of the atmosphere (in terms of surface pressure and atmospheric composition) on this feedback, since an atmosphere was neglected in previous studies. A plane-parallel radiative transfer model was used for the calculation of planetary albedos. We varied CO 2 partial pressures as well as the H 2 O, CH 4 , and O 3 content in the atmosphere for planets orbiting Sun-like and M type stars.Results suggest that, for planets around M stars, the ice-albedo effect is significantly reduced, compared to planets around Sun-like stars. Including the effects of an atmosphere further suppresses the sensitivity to the icealbedo effect. Atmospheric key properties such as surface pressure, but also the abundance of radiative trace gases, can considerably change the strength of the ice-albedo feedback. For dense CO 2 atmospheres of the order of a few to tens of bar, atmospheric rather than surface properties begin to dominate the planetary radiation budget. At high CO 2 pressures, the ice-albedo feedback is strongly reduced for planets around M stars. The presence of trace amounts of H 2 O and CH 4 in the atmosphere also weakens the ice-albedo effect for both stellar types considered. For planets around Sun-like stars, O 3 could also lead to a very strong decrease of the ice-albedo feedback at high CO 2 pressures.

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“…(7.67) and (7.71) in Petty (2006)]. Among the cases we examined, only the case with S cr 5 1 and N * 5 5 3 10 24 kg 21 provides a combination of particle radius (35 mm) and cloud optical thickness (t ; 5), which is within the range favorable for scattering greenhouse effect (Mischna et al 2000;Forget et al 2013;Kitzmann et al 2013). In other cases, the cloud development seems to be too infrequent, or the cloud layer is optically too thick.…”

mentioning

confidence: 94%

“…Investigation of possible structures of circulation fields and properties of clouds in such an atmosphere, especially a dense CO 2 atmosphere, is not only interesting as a problem of fluid mechanics, but also as an important target of research on the early Mars, where the scattering greenhouse effect of CO 2 ice cloud could have played an indispensable role in maintaining possible warm climate (Forget and Pierrehumbert 1997;Mischna et al 2000;Colaprete and Toon 2003;Mitsuda 2007;Forget et al 2013). Previous studies have shown that the intensity of scattering greenhouse effect depends on a number of cloud properties, such as the size distribution of cloud particles, optical depth, cloud cover, and cloud height (Forget and Pierrehumbert 1997;Mischna et al 2000;Kitzmann et al 2013). For the advancement of our understanding on the early Martian climate, it is, therefore, valuable to investigate possible properties of CO 2 clouds consistent with circulation fields of convection associated with condensation of the major atmospheric constituent.…”

Section: Introductionmentioning

confidence: 99%

“…It is not trivial to anticipate how the results of the present experiment are modified when the idealistic body cooling is replaced by a sophisticated radiative process. It could be computationally demanding task, considering the recent research of Kitzmann et al (2013), where a discrete ordinate method with 24 streams is employed to demonstrate that conventional two-stream approximation significantly overestimates scattering greenhouse effects. Experiments including absorption and scattering of radiation by CO 2 gas and CO 2 ice cloud, as well as diurnal variation of insolation and ground temperature, are left for future work.…”

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confidence: 99%

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A Numerical Study of Convection in a Condensing CO2 Atmosphere under Early Mars-Like Conditions

Yamashita

Odaka

Sugiyama

et al. 2016

Journal of the Atmospheric Sciences

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Cloud convection of a CO 2 atmosphere where the major constituent condenses is numerically investigated under a setup idealizing a possible warm atmosphere of early Mars, utilizing a two-dimensional cloudresolving model forced by a fixed cooling profile as a substitute for a radiative process. The authors compare two cases with different critical saturation ratios as condensation criteria and also examine sensitivity to number mixing ratio of condensed particles given externally.When supersaturation is not necessary for condensation, the entire horizontal domain above the condensation level is continuously covered by clouds irrespective of number mixing ratio of condensed particles. Horizontal-mean cloud mass density decreases exponentially with height. The circulations below and above the condensation level are dominated by dry cellular convection and buoyancy waves, respectively. When 1.35 is adopted as the critical saturation ratio, clouds appear exclusively as intense, short-lived, quasiperiodic events. Clouds start just above the condensation level and develop upward, but intense updrafts exist only around the cloud top; they do not extend to the bottom of the condensation layer. The cloud layer is rapidly warmed by latent heat during the cloud events, and then the layer is slowly cooled by the specified thermal forcing, and supersaturation gradually develops leading to the next cloud event. The periodic appearance of cloud events does not occur when number mixing ratio of condensed particles is large.

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Clouds in the atmospheres of extrasolar planets

Cited by 36 publications

References 37 publications

Comparison of “warm and wet” and “cold and icy” scenarios for early Mars in a 3‐D climate model

Comparison of “warm and wet” and “cold and icy” scenarios for early Mars in a 3‐D climate model

The Dependence of the Ice-Albedo Feedback on Atmospheric Properties

A Numerical Study of Convection in a Condensing CO2 Atmosphere under Early Mars-Like Conditions

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