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arXiv 1605.09545astro-ph.EP
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连接点III:夜侧冷却和表面摩擦影响潮汐锁定的类地行星的气候

Connecting the dots III: Night side cooling and surface friction affect climates of tidally locked terrestrial planets

L. Carone, R. Keppens, L. Decin

摘要:

我们研究了夜面冷却和表面摩擦如何影响潮汐锁定类地行星的表面温度和大尺度环流。对于每一种情况,我们改变轨道周期之间的$P_{rot}=1-100$天和捕捉气候状态的变化。我们发现,在不同的表面摩擦的情况下,气候状态的剧烈变化。对于非常有效的表面摩擦($t_{s,fric}=$ 0.1天),短旋转周期($P_{rot} \leq$ 10天)的模拟显示,主要是常设的热带Rossby波。这些波导致两个高纬西风急流和未扰动纬向直接环流的气候状态。在大多数其他情景中,短旋转周期的模拟反而表现出热带Rossby波的优势。这种气候状态有一个单一的赤道西风急流,破坏了直接环流。弱表面摩擦($t_{s,fric}=~10 -100$天)的实验表明,表面温度和环流之间的解耦,这导致了强烈的冷却的夜侧。$t_{s,fric}= 100$天的实验假设气候状态为东风气流(逆行旋转),为中等和缓慢的行星旋转$P_{rot}= 12 - 100$天。结果表明,与标称模型相比,夜侧冷却效率提高一个数量级,夜侧表面温度降低80-100 K。同时,地表昼侧温度仅下降25 K.热力强迫的增加抑制了小行星($R_P=1 R_{Earth}$)在短旋转周期制度($P_{rot} \leq$ 10天)的额外热带Rossby波的形成。

英文摘要:

We investigate how night side cooling and surface friction impact surface temperatures and large scale circulation for tidally locked Earth-like planets. For each scenario, we vary the orbital period between $P_{rot}=1-100$~days and capture changes in climate states. We find drastic changes in climate states for different surface friction scenarios. For very efficient surface friction ($t_{s,fric}=$ 0.1 days), the simulations for short rotation periods ($P_{rot} \leq$ 10 days) show predominantly standing extra tropical Rossby waves. These waves lead to climate states with two high latitude westerly jets and unperturbed meridional direct circulation. In most other scenarios, simulations with short rotation periods exhibit instead dominance by standing tropical Rossby waves. Such climate states have a single equatorial westerly jet, which disrupts direct circulation. Experiments with weak surface friction ($t_{s,fric}=~10 -100$ days) show decoupling between surface temperatures and circulation, which leads to strong cooling of the night side. The experiment with $t_{s,fric}= 100$ days assumes climate states with easterly flow (retrograde rotation) for medium and slow planetary rotations $P_{rot}= 12 - 100$~days. We show that an increase of night side cooling efficiency by one order of magnitude compared to the nominal model leads to a cooling of the night side surface temperatures by 80-100~K. The day side surface temperatures only drop by 25~K at the same time. The increase in thermal forcing suppresses the formation of extra tropical Rossby waves on small planets ($R_P=1 R_{Earth}$) in the short rotation period regime ($P_{rot} \leq$ 10 days).

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