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arXiv 1504.07474astro-ph.EP
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模拟类地行星的地面温度

Modeling the surface temperature of Earth-like planets

G. Vladilo, L. Silva, G. Murante, L. Filippi, A. Provenzale

摘要:

基于行星地面温度的时空分布,提出了一种新的类地行星地面温度模型(ESTM)。ESTM采用了一个表面能平衡模式,并辅以:辐射对流大气柱计算,一套基于物理的对流输送参数化,以及比标准EBM更精确的地面和云特性描述。该参数化方法适用于大气层较浅、轴对称度适中(θ>= 45 ^o)的旋转类地行星。与文献中的三维大气动力学模式的比较表明,当自转速率、日射量、表面气压和行星半径在0.5 ≤ Ω/Ω_o ≤ 2,0.75 ≤ S/S_o ≤ 1.25,0.3 ≤ p/(1 bar)≤ 10,0.5 ≤ R/R_o ≤ 2。ESTM具有极低的计算成本,并且可以在行星参数几乎不知道(如对于大多数系外行星)和/或需要针对不同参数配置进行多次运行时使用。对一颗测试案例系外行星(开普勒-62 e)的模型模拟表明,在类地行星预期范围内的表面压力的不确定性可能会对平均温度产生约60 K的影响。在ESTM的有效性范围内,表面压力的影响大于由旋转速率、轴向刚度和海洋分数的不确定性所预测的影响。我们讨论了利用ESTM的灵活性进行行星可居住性的统计排名的可能性。

英文摘要:

We introduce a novel Earth-like planet surface temperature model (ESTM) for habitability studies based on the spatial-temporal distribution of planetary surface temperatures. The ESTM adopts a surface Energy Balance Model complemented by: radiative-convective atmospheric column calculations, a set of physically-based parameterizations of meridional transport, and descriptions of surface and cloud properties more refined than in standard EBMs. The parameterization is valid for rotating terrestrial planets with shallow atmospheres and moderate values of axis obliquity (epsilon >= 45^o). Comparison with a 3D model of atmospheric dynamics from the literature shows that the equator-to-pole temperature differences predicted by the two models agree within ~5K when the rotation rate, insolation, surface pressure and planet radius are varied in the intervals 0.5 <= Omega/Omega_o <= 2, 0.75 <= S/S_o <= 1.25, 0.3 <= p/(1 bar) <= 10, and 0.5 <= R/R_o <= 2, respectively. The ESTM has an extremely low computational cost and can be used when the planetary parameters are scarcely known (as for most exoplanets) and/or whenever many runs for different parameter configurations are needed. Model simulations of a test-case exoplanet (Kepler-62e) indicate that an uncertainty in surface pressure within the range expected for terrestrial planets may impact the mean temperature by ~60 K. Within the limits of validity of the ESTM, the impact of surface pressure is larger than that predicted by uncertainties in rotation rate, axis obliquity, and ocean fractions. We discuss the possibility of performing a statistical ranking of planetary habitability taking advantage of the flexibility of the ESTM.

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