The atmospheric circulation of tidally locked planets is dominated by a superrotating eastward equatorial jet. We develop a predictive theory for the formation of this jet, proposing a mechanism in which the three-dimensional stationary waves induced by the day-night forcing gradient produce an equatorial acceleration. This is balanced in equilibrium by an interaction between the resulting jet and the vertical motion of the atmosphere. The three-dimensional structure of the zonal acceleration is vital to this mechanism. We demonstrate this mechanism in a hierarchy of models. We calculate the three-dimensional stationary waves induced by the forcing on these planets, and show the vertical structure of the zonal acceleration produced by these waves, which we use to suggest a mechanism for how the jet forms. GCM simulations are used to confirm the equilibrium state predicted by this mechanism, where the acceleration from these waves is balanced by an interaction between the zonal-mean vertical velocity and the jet. We derive a simple model of this using the "Weak Temperature Gradient" approximation, which gives an estimate of the jet speed on a terrestrial tidally locked planet. We conclude that the proposed mechanism is a good description of the formation of an equatorial jet on a terrestrial tidally locked planet, and should be useful for interpreting observations and simulations of these planets. The mechanism requires assumptions such as a large equatorial Rossby radius and weak acceleration due to transient waves, and a different mechanism may produce the equatorial jets on gaseous tidally locked planets.

中文翻译：

---

潮汐锁定行星上的赤道喷射速度。一、类地行星

潮汐锁定行星的大气环流主要由向东超转的赤道急流主导。我们开发了这种喷流形成的预测理论，提出了一种由昼夜强迫梯度引起的三维驻波产生赤道加速度的机制。这通过产生的射流和大气垂直运动之间的相互作用达到平衡。纬向加速度的三维结构对该机制至关重要。我们在模型的层次结构中演示了这种机制。我们计算了由这些行星上的强迫引起的三维驻波，并显示了这些波产生的纬向加速度的垂直结构，我们用它来提出喷射形成的机制。GCM 模拟用于确认由这种机制预测的平衡状态，其中这些波的加速度通过纬向平均垂直速度和射流之间的相互作用来平衡。我们使用“弱温度梯度”近似推导出了一个简单的模型，该模型给出了地球潮汐锁定行星上喷流速度的估计值。我们得出的结论是，所提出的机制很好地描述了地球潮汐锁定行星上赤道急流的形成，并且应该有助于解释对这些行星的观察和模拟。该机制需要假设诸如大的赤道罗斯比半径和瞬态波导致的弱加速度等假设，而不同的机制可能会在气态潮汐锁定行星上产生赤道喷流。