标题： 地球大气向超级旋转的转变 显示英文标题

标题： The Transition to Superrotation in Terrestrial Atmospheres

摘要： 我们证明，通过改变一个无量纲数——热罗斯贝数，仅由轴对称强迫驱动的全球大气模拟从类似地球的大气转变为更类似于金星或土卫六大气的超级自转大气。 当在中间和高纬度由斜压不稳定产生的向赤道传播的罗斯贝波被抑制时，超级自转转变发生，这种情况会在变形半径超过行星半径时出现。 在较大的热罗斯贝数下，在初始的几乎轴对称阶段之后，由混合斜压-斜温和不稳定性产生的东西向波数为一的全球性斜压波主导了东西向动量的涡动通量。 该全球波在自旋启动期间将向东的东西向动量汇聚到赤道，并在超级自转显现之前在中间纬度沉积向西的动量，一旦超级自转建立，斜压不稳定性就会停止。 由高、低纬度斜压不稳定性混合产生的一种东西向波数为一的全球性斜率模式负责维持统计稳态下的超级自转。 在中间的热罗斯贝数下，全球斜压模的动量通量相对于较小的斜压模来说处于次主导地位，因此不会发展出强烈的超级自转。 显示英文摘要

摘要： We show that by changing a single non-dimensional number, the thermal Rossby number, global atmospheric simulations with only axisymmetric forcing pass from an Earth-like atmosphere to a superrotating atmosphere that more resembles the atmospheres of Venus or Titan. The transition to superrotation occurs under conditions in which equatorward-propagating Rossby waves generated by baroclinic instability at intermediate and high latitudes are suppressed, which will occur when the deformation radius exceeds the planetary radius. At large thermal Rossby numbers following an initial, nearly axisymmetric phase, a global baroclinic wave of zonal wavenumber one generated by mixed barotropic-baroclinic instability dominates the eddy flux of zonal momentum. The global wave converges eastward zonal momentum to the equator and deposits westward momentum at intermediate latitudes during spinup and before superrotation emerges, and the baroclinic instability ceases once superrotation is established. A global barotropic mode of zonal wavenumber one generated by a mix of high- and low-latitude barotropic instability is responsible for maintaining superrotation in the statistically steady state. At intermediate thermal Rossby numbers, momentum flux by the global baroclinic mode is subdominant relative to smaller baroclinic modes, and thus strong superrotation does not develop.