Battalio J Michael, Lora Juan M
Department of Earth and Planetary Sciences, Yale University, 210 Whitney Ave., New Haven, CT 06511.
Geophys Res Lett. 2021 Sep 28;48(18). doi: 10.1029/2021gl094244. Epub 2021 Sep 13.
One of the first large cloud systems ever observed on Titan was a stationary event at the southern pole that lasted almost two full Titan days. Its stationary nature and large extent are puzzling given that low-level winds should transport clouds eastward, pointing to a mechanism such as atmospheric waves propagating against the mean flow. We use a composite of 47 large convective events across 15 Titan years of simulations from the Titan Atmospheric Model to show that Rossby waves trigger polar convection-which halts the waves and produces stationary precipitation-and then communicate its impact globally. In the aftermath of the convection, forced waves undergo a complicated evolution, including cross-equatorial propagation and tropical-extratropical interaction. The resulting global impact from convection implies its detectability anywhere on Titan, both via surface measurements of pressure and temperature and through remote observation of the outgoing longwave radiation, which increases by ~0.5% globally.
土卫六上最早观测到的大型云系之一是发生在南极的一个静止事件，持续了几乎整整两个土卫六日。考虑到低层风应该会将云层向东输送，其静止的特性和广阔的范围令人费解，这表明存在一种机制，比如大气波逆着平均气流传播。我们使用土卫六大气模型在15个土卫六年的模拟中对47个大型对流事件进行合成分析，结果表明罗斯贝波触发极地对流，这会使波停止并产生静止降水，然后将其影响传递到全球。在对流之后，受迫波会经历复杂的演化，包括跨赤道传播和热带 - 温带相互作用。对流产生的全球影响意味着在土卫六的任何地方都可以检测到它，既可以通过对压力和温度的地面测量，也可以通过对向外长波辐射的遥感观测，全球向外长波辐射增加了约0.5%。
