Abstract As a boundary condition, the lower bound is a prerequisite for constructing the Budyko framework. However, the traditional lower bound i.e., the horizontal axis is an analytical boundary without considering realistic conditions. In fact, under real-word condition, the lower bound of Budyko curves, representing the maximum value of water yield, should be located above the horizontal axis due to complicated constraints from basin characteristics, especially the precipitation seasonality, a key driver of runoff yield and a dominant factor in constructing Budyko framework. Thus, this study focused on exploring the reasonable location of the lower bound by adequately analyzing potential influence of precipitation seasonality. To do that, multiple hydrological simulations in basins under different climate and topography conditions were developed based on various precipitation scenarios constructed by using Markov chain with full range of precipitation seasonality. To fully understand the influence from precipitation seasonality on the lower bound, the water-energy supply and the basin characteristics were fixed by aridity index and hydrological model parameters, respectively. The results reveal a positive correlation between runoff coefficient and precipitation seasonality with an obvious higher location above the horizontal axis, indicating the horizontal axis is imprecise to describe the upper bound of runoff yield under real-word condition. Furthermore, a potential location of the lower bound above the horizontal axis in Budyko space was found based on runoff yield mechanism under real basin condition, representing a more appropriate boundary condition of Budyko framework.

中文翻译：

---

关于布迪科曲线的下界：降水季节性的影响

摘要 作为边界条件，下界是构建Budyko框架的前提。然而，传统的下界即水平轴是没有考虑现实条件的解析边界。事实上，在现实条件下，代表产水量最大值的布迪科曲线的下界，由于流域特征的复杂约束，特别是降水季节性，是产水量的一个关键驱动因素，应该位于横轴上方。以及构建 Budyko 框架的主导因素。因此，本研究着眼于通过充分分析降水季节性的潜在影响，探索下限的合理位置。要做到这一点，基于使用马尔可夫链构建的各种降水情景，开发了不同气候和地形条件下流域的多种水文模拟，具有全范围的降水季节性。为充分了解降水季节性对下限的影响，分别通过干旱指数和水文模型参数确定水能供应和流域特征。结果表明，径流系数与降水季节性呈正相关，横轴上方位置明显偏高，说明横轴不能准确描述实况下产流量的上限。此外，