SUMMA 2.0.0 develop (2020-06-12)

SUMMA (Clark et al., 2015a;b;c) is a hydrologic modeling framework that can be used for the systematic analysis of alternative model conceptualizations with respect to flux parameterizations, spatial configurations, and numerical solution techniques. It can be used to configure a wide range of hydrological model alternatives and we anticipate that systematic model analysis will help researchers and practitioners understand reasons for inter-model differences in model behavior. When applied across a large sample of catchments, SUMMA may provide insights in the dominance of different physical processes and regional variability in the suitability of different modeling approaches. An important application of SUMMA is selecting specific physics options to reproduce the behavior of existing models – these applications of "model mimicry" can be used to define reference (benchmark) cases in structured model comparison experiments, and can help diagnose weaknesses of individual models in different hydroclimatic regimes.

SUMMA is built on a common set of conservation equations and a common numerical solver, which together constitute the “structural core” of the model. Different modeling approaches can then be implemented within the structural core, enabling a controlled and systematic analysis of alternative modeling options, and providing insight for future model development.

The important modeling features are:
The formulation of the conservation model equations is cleanly separated from their numerical solution;
Different model representations of physical processes (in particular, different flux parameterizations) can be used within a common set of conservation equations; and
The physical processes can be organized in different spatial configurations, including model elements of different shape and connectivity (e.g., nested multi-scale grids and HRUs).

SUMMA（Clark 等人，2015a;b;c）是一种水文建模框架，适用于对模型概念化、通量参数化、空间配置和数值求解技术等方面的系统性分析。该框架能够配置多种水文模型替代方案，我们预期系统的模型分析将有助于研究人员和实践者理解模型行为之间相互差异的原因。当应用于大量流域样本时，SUMMA 可以为不同建模方法在适宜性方面的区域差异以及不同物理过程的支配性提供洞见。SUMMA 的重要应用之一是选择特定的物理选项来重现现有模型的行为——这种‘模型模仿’的应用可以用于定义结构化模型比较实验中的参考（基准）案例，并有助于诊断不同气候水文条件下个别模型的弱点。

SUMMA 建立在共同的守恒方程和共同的数值求解器之上，这两者共同构成了模型的‘结构核心’。不同的建模方法可以在结构核心中实施，从而实现对替代建模选项的受控和系统性分析，并为未来的模型发展提供见解。

模型的重要特性包括：
- 守恒模型方程的表述与其数值求解被清晰地区分开来；
- 在共同的守恒方程组中，可以采用不同的物理过程模型表示（特别是不同的通量参数化）；
- 物理过程可以组织在不同的空间配置中，包括不同形状和连通性的模型元素（例如，嵌套的多尺度网格和HRU）。