The circulation pattern and day-night heat transport in the atmosphere of a synchronously rotating aquaplanet: Dependence on planetary rotation rate
The circulation pattern and day-night heat transport in the atmosphere of a synchronously rotating aquaplanet: Dependence on planetary rotation rate
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DOI：
10.1016/j.icarus.2016.09.004
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发表时间：
2017-01
期刊：
影响因子：
3.2
通讯作者：
Satoshi Noda;M. Ishiwatari;K. Nakajima;Y. Takahashi;S. Takehiro;M. Onishi;G. Hashimoto;K. Kuramoto-K.-Kur
中科院分区：
文献类型：
--
作者：
Satoshi Noda;M. Ishiwatari;K. Nakajima;Y. Takahashi;S. Takehiro;M. Onishi;G. Hashimoto;K. Kuramoto-K.-Kur
为了研究同步旋转的水行星上可能出现的各种大气状态，利用简化的水文和辐射过程的大气环流模式（GCM）进行了一个研究行星自转速率影响的实验。整个行星表面覆盖着沼泽海洋。行星自转速率的值从零到地球的值变化，而其他参数，如行星半径，大气干组分的平均分子量和总质量，以及太阳常数被设置为现在的地球值。积分结果表明，大气达到统计平衡状态的所有运行，没有计算的情况下证实失控的温室状态。得到的环流型被分为四种类型：Ⅰ型的特点是昼夜热直接环流的优势，Ⅱ型的特点是纬向波1号共振Rossby波赤道上的纬向广泛的西风急流，Ⅲ型的特点是长时间尺度的南北不对称变化，和Ⅳ型的特点是一对中纬度西风急流。随着行星自转速率的增加，环流由Ⅰ型向Ⅱ型再向Ⅲ型逐渐平稳地演变，而由Ⅲ型向Ⅳ型的转变则是突变的、不连续的。在行星自转速率的有限范围内，第三型和第四型都以统计稳定状态出现，构成多重平衡。尽管环流发生了实质性的变化，但从昼侧到夜侧的净能量输送几乎对行星自转速率不敏感，尽管干静能和潜热能输送的划分发生了变化。这种显著的不敏感性的原因是，在白天一侧的广阔区域上的出射长波辐射受到潮湿大气的辐射极限的限制，因此到夜晚一侧的传输（由入射太阳辐射和辐射极限之间的差确定）不会发生很大的变化。
In order to investigate a possible variety of atmospheric states realized on a synchronously rotating aquaplanet, an experiment studying the impact of planetary rotation rate is performed using an atmospheric general circulation model (GCM) with simplified hydrological and radiative processes. The entire planetary surface is covered with a swamp ocean. The value of planetary rotation rate is varied from zero to the Earth’s, while other parameters such as planetary radius, mean molecular weight and total mass of atmospheric dry components, and solar constant are set to the present Earth’s values. The integration results show that the atmosphere reaches statistically equilibrium states for all runs; none of the calculated cases exemplifies the runaway greenhouse state. The circulation patterns obtained are classified into four types: Type-I characterized by the dominance of a day-night thermally direct circulation, Type-II characterized by a zonal wave number one resonant Rossby wave over a meridionally broad westerly jet on the equator, Type-III characterized by a long time scale north-south asymmetric variation, and Type-IV characterized by a pair of mid-latitude westerly jets. With the increase of planetary rotation rate, the circulation evolves from Type-I to Type-II and then to Type-III gradually and smoothly, whereas the change from Type-III to Type-IV is abrupt and discontinuous. Over a finite range of planetary rotation rate, both Types-III and -IV emerge as statistically steady states, constituting multiple equilibria. In spite of the substantial changes in circulation, the net energy transport from the day side to the night side remains almost insensitive to planetary rotation rate, although the partition into dry static energy and latent heat energy transports changes. The reason for this notable insensitivity is that the outgoing longwave radiation over the broad area of the day side is constrained by the radiation limit of a moist atmosphere, so that the transport to the night side, which is determined as the difference between the incoming solar radiation and the radiation limit, cannot change greatly.