Rossby number dependence of Venus/Titan‐type superrotation and its related intermittency
Rossby number dependence of Venus/Titan‐type superrotation and its related intermittency
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金星/泰坦型超自转的罗斯贝数依赖性及其相关的间歇性
DOI：
10.1029/2020je006637
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Masaaki Takahashi
中科院分区：
文献类型：
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作者：
Yuma Tsunoda;Masaru Yamamoto;Masaaki Takahashi
用理想的大气环流模式研究了由平流层加热驱动的金星/泰坦型超自转和超自转动力学中的间歇性。当喷流核的Rossby数为∼23时，行星尺度的快速Rossby波被正压和斜压能量转换瞬时放大，并间歇性地产生赤道涡动动量通量。在高纬度地区，斜压涡的向极涡热通量较大时，也会发生向极涡的动量输送。在这样一颗缓慢旋转或较小的行星上，在极地间接环流存在的情况下，赤道超旋转是通过微弱的、间歇性的赤道方向的动量通量有效地发展起来的，并且纬向流的速度在中低纬度地区基本恒定。相反，在相对较快或较大的行星上，当喷流核的Rossby数为∼7.5时，尽管纬向急流和向赤道的涡动量通量增强，但赤道超旋并没有得到有效的发展(即超旋强度和赤道效率很小)。强经向环流发展的急流赤道方向侧的慢正压Rossby波连续产生向赤道方向的强涡动通量。极地斜压波的热通量可以忽略不计，因为它比纬向平均经向环流的热通量小得多。
Venus/Titan‐type superrotation driven by stratospheric heating and intermittency seen in the superrotation dynamics are investigated using an idealized general circulation model in a high Rossby number regime (Ro= 7.5 to 23 for the strongest zonal jet) where the superrotation is formed by the meridional circulation and equatorward eddy momentum flux. When the jet core has a Rossby number of ∼23 on a slowly rotating or small planet, fast planetary‐scale Rossby waves are transiently amplified by both barotropic and baroclinic energy conversion and intermittently produce equatorward eddy momentum fluxes. At high latitudes, poleward eddy momentum transport also occurs when the poleward heat flux of baroclinic eddies is strong. On such a slowly rotating or small‐sized planet, equatorial superrotation is developed efficiently by weak, intermittent equatorward momentum flux in the presence of polar indirect circulation and the speed of the zonal flow is roughly constant over the low‐ and mid‐latitudes. In contrast, on a relatively fast rotating or large‐sized planet when the Rossby number is ∼7.5 for the jet core, although the zonal jets and equatorward eddy momentum fluxes intensify, equatorial superrotation is not developed efficiently (i.e., the superrotation intensity and its equatorial efficiency are small). Strong equatorward eddy momentum fluxes are produced continuously by slow barotropic Rossby waves on the equatorward flanks of the jets developed by the strong meridional circulation. The poleward heat fluxes of baroclinic waves are negligible because it is much smaller than the heat flux of the zonal‐mean meridional circulation.