Atmospheric Circulation of Hot Jupiters: Three-dimensional Circulation Models of HD 209458b and HD 189733b with Simplified Forcing
Atmospheric Circulation of Hot Jupiters: Three-dimensional Circulation Models of HD 209458b and HD 189733b with Simplified Forcing
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热木星的大气环流：具有简化强迫的 HD 209458b 和 HD 189733b 的三维环流模型
DOI：
10.1086/589325
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
M. Marley
中科院分区：
文献类型：
--
作者：
A. Showman;C. Cooper;J. Fortney;M. Marley
我们对HD 209458b和HD 189733b的大气环流进行了全球三维数值模拟，并计算了这些模拟预测的红外光谱和光曲线，并与现有观测结果进行了比较。用简化的牛顿松弛格式参数化辐射加热/冷却。我们的模拟显示昼夜温度的差异随着压力的变化而变化很大。在低气压下（<10毫巴），空气从亚恒星点流向反恒星点，沿赤道和两极上空都有。在较深的层次上，气流发展成一个向东的赤道急流，速度为3-4 km s - 1，在高纬度地区向西气流较弱。这种基本流型对模型分辨率、重力、辐射时间常数和初始温度结构的变化具有鲁棒性。夜侧光谱显示H2O， CO和/或CH4的深吸收带，而在白天，这些吸收带变平甚至翻转为发射。这是由于动力对垂直温度-压力结构的强烈影响；夜侧温度随海拔高度的升高而急剧下降，而日侧温度则趋于等温。在斯皮策带通中，根据波长和化学性质，我们预测的行星与恒星的通量比随轨道相位变化约2-10倍。对于HD 189733b，我们获得了详细的8 μm光曲线，我们正确地给出了观测到的通量最大值的相位偏移，但我们没有解释通量最小值，并且我们高估了总通量变化。这种差异可能是由于牛顿松弛方案固有的简化造成的，并为在未来的研究中纳入实际的辐射传输提供了动力。
We present global, three-dimensional numerical simulations of the atmospheric circulation on HD 209458b and HD 189733b and calculate the infrared spectra and light curves predicted by these simulations, which we compare with available observations. Radiative heating/cooling is parameterized with a simplified Newtonian relaxation scheme. Our simulations develop day-night temperature contrasts that vary strongly with pressure. At low pressure (<10 mbar), air flows from the substellar point toward the antistellar point, both along the equator and over the poles. At deeper levels, the flow develops an eastward equatorial jet with speeds of 3-4 km s−1, with weaker westward flows at high latitudes. This basic flow pattern is robust to variations in model resolution, gravity, radiative time constant, and initial temperature structure. Nightside spectra show deep absorption bands of H2O, CO, and/or CH4, whereas on the dayside these absorption bands flatten out or even flip into emission. This results from the strong effect of dynamics on the vertical temperature-pressure structure; the temperature decreases strongly with altitude on the nightside but becomes almost isothermal on the dayside. In Spitzer bandpasses, our predicted planet-to-star flux ratios vary by a factor of ~2-10 with orbital phase, depending on the wavelength and chemistry. For HD 189733b, where a detailed 8 μm light curve has been obtained, we correctly produce the observed phase offset of the flux maximum, but we do not explain the flux minimum and we overpredict the total flux variation. This discrepancy likely results from the simplifications inherent in the Newtonian relaxation scheme and provides motivation for incorporating realistic radiative transfer in future studies.