Planetary surfaces beyond Earth’s are impacted by surface hydrology, and exhibit fluvial and lacustrine features. Titan in particular harbours a rich hydroclimate replete with valley networks, lakes, seas and putative wetlands, all of which are pronounced in the lower-elevation polar regions. However, understanding of Titan’s global climate has heretofore neglected the hydraulic influence of Titan’s large-scale topography. Here we add a surface hydrology model to an existing Titan atmospheric model, and find that infiltration, groundmethane evaporation, and surface and subsurface flow are fundamental to simultaneously reproducing Titan’s observed surface liquid distribution and other aspects of its climate system. We propose that Titan’s climate features infiltration into unsaturated low- and mid-latitude highlands and surface or subsurface flow into high-latitude basins, producing the observed polar moist climes and equatorial deserts. This result implies that a potentially massive unobserved methane reservoir participates in Titan’s methane cycle. It also illustrates the importance of surface hydrology in Titan climate models, and by extension suggests the influence of surface hydrology in idealized models of other planetary climates, including the climates and palaeoclimates of Earth, Mars and exoplanets.

地球以外的行星表面受到地表水文学的影响，并表现出河流和湖泊特征。特别是土卫六拥有丰富的水文气候，那里有山谷网络，湖泊，海洋和假定的湿地，所有这些在海拔较低的极地地区都很明显。但是，迄今为止，对土卫六全球气候的了解忽略了土卫六大规模地形的水力影响。在这里，我们在现有的泰坦大气模型中添加了地表水文模型，发现渗透，地面甲烷蒸发以及地表和地下流量是同时再现泰坦观测到的地表液体分布及其气候系统其他方面的基础。我们认为，土卫六的气候特征是渗透到不饱和的低纬度和中纬度高地，地表或地下流流入高纬度盆地，从而产生观测到的极地潮湿气候和赤道沙漠。该结果表明，潜在的大量未观测到的甲烷储层参与了土卫六的甲烷循环。它还说明了地表水文学在土卫六气候模型中的重要性，并通过扩展提出了地表水文学在其他行星气候（包括地球，火星和系外行星的气候和古气候）的理想化模型中的影响。