3:30 PM - 3:45 PM
[MIS17-07] An atmospheric general circulation model experiment on land planet with increased solar constant
Keywords:land planet, atmospheric general circulation model, solar constant, existence condition of liquid water, habitability, complete evaporation
A land planet possesses much less water than the ocean of the Earth (Abe et al., 2005) and is considered as a possible kind of exoplanets. Abe et al. (2011) performed a AGCM (atmospheric general circulation model) experiment using a land planet configuration, and showed that a land planet with zero of obliquity possesses liquid water on its surface for the values of solar constant between 1500W/m2 and 2300W/m2. This result means that a land planet can possess liquid water for wider range of solar constant than an aquaplanet which is a planet covered with the ocean all over the surface, and suggests that the climate of land planets is an important problem for considering the existence condition of liquid water on planet surfaces. In this study, we reexamine the climate of a land planet in order to obtain the understanding of the existence condition of liquid water on land planet.
The model utilized in this study is DCPAM5 (http://www.gfd-dennou.org/library/dcpam, Noda et al., 2017). It is a three-dimensional primitive system on a sphere. The equations are discretized horizontally by spherical spectral transform method using spherical harmonics. We used sigma (pressure normalized by surface pressure) as the vertical coordinate, which is discretized by following the method of Arakawa and Suarez (1983). As for the radiation processes, the schemes of Chou and Lee (1996) and Chou et al. (2001) are used. For the cumulus parameterization, the relaxed Arakawa-Schubert scheme (Moorthy and Suarez, 1992) is used. Vertical turbulent mixing is represented by the level II scheme of Mellor and Yamada (1974). The surface fluxes of momentum, sensible heat, and latent heat are evaluated by following Louis (1979). The advection of water vapor and cloud water are calculated with the semi-Lagrangian scheme of Kashimura et al. (2013). A bucket model (Manabe, 1969) is applied to all surface. The value of solar constant is varied from 1366 W/m2 to 2400 W/m2. The value of planetary rotation rate is set to Earth's value. Initial amount of soil water is equivalent to a layer of water 40cm thick. As for model resolution, horizontal spherical harmonics expansion is truncated at total wavenumber 21, and the number of vertical layers is 26. We use two values of obliquity, those are 23.4 degree and 0 degree.
In our experiment with 0 degree of obliquity, which is the same configuration as that of Abe et al. (2011), liquid water remains to exist at surface and complete evaporation of soil water does not occur for 2400 W/m2 of solar constant. This result is different from that of Abe et al (2011) who showed that surface liquid water disappeared for 2300 W/m2 of solar constant. In the presentation of JpGU meeting, we will discuss the existence condition of liquid water on land planet surface including results of obliquity dependence experiments.
The model utilized in this study is DCPAM5 (http://www.gfd-dennou.org/library/dcpam, Noda et al., 2017). It is a three-dimensional primitive system on a sphere. The equations are discretized horizontally by spherical spectral transform method using spherical harmonics. We used sigma (pressure normalized by surface pressure) as the vertical coordinate, which is discretized by following the method of Arakawa and Suarez (1983). As for the radiation processes, the schemes of Chou and Lee (1996) and Chou et al. (2001) are used. For the cumulus parameterization, the relaxed Arakawa-Schubert scheme (Moorthy and Suarez, 1992) is used. Vertical turbulent mixing is represented by the level II scheme of Mellor and Yamada (1974). The surface fluxes of momentum, sensible heat, and latent heat are evaluated by following Louis (1979). The advection of water vapor and cloud water are calculated with the semi-Lagrangian scheme of Kashimura et al. (2013). A bucket model (Manabe, 1969) is applied to all surface. The value of solar constant is varied from 1366 W/m2 to 2400 W/m2. The value of planetary rotation rate is set to Earth's value. Initial amount of soil water is equivalent to a layer of water 40cm thick. As for model resolution, horizontal spherical harmonics expansion is truncated at total wavenumber 21, and the number of vertical layers is 26. We use two values of obliquity, those are 23.4 degree and 0 degree.
In our experiment with 0 degree of obliquity, which is the same configuration as that of Abe et al. (2011), liquid water remains to exist at surface and complete evaporation of soil water does not occur for 2400 W/m2 of solar constant. This result is different from that of Abe et al (2011) who showed that surface liquid water disappeared for 2300 W/m2 of solar constant. In the presentation of JpGU meeting, we will discuss the existence condition of liquid water on land planet surface including results of obliquity dependence experiments.