面向大型复杂冰川的分布式水文模拟研究

Despite the small number of large glaciers with area greater than 20 square kilometers, they concentrate more than half of the glacier resources, and dominate the regional glacial meltwater runoff in western China. Glacial runoff analysis with physically-based distributed hydrological model is still in its infancy at home and abroad, and for large glaciers with complicated generation and concentration mechanisms, such attempts are very little due to difficulties in field observations and scarcities in model data. Runoff assessments using physically-based distributed glacio-hydrological model can provide insights into the composition and influencing factors of the different sources in glacier meltwater, and the formation mechanism and the constraints of the glacier meltwater runoff, so as to provide sophisticated tools and basis for the assessment of the trend of glacial meltwater in the context of climate change. Using Koxkar Glacier as a case study, the proposed project will carry out studies on the mechanisms of glacial runoff generation and concentration through continuous field observations and targeted experiments, to clarify the characteristics of key processes of glacial meltwater runoff changes and revent influencing factors. Based on the understanding of specific runoff processes, the corresponding parameterization scheme will be established, which helps to establish the physically-based distributed hydrological model (DGRM) for glacierized area. By means of integrated model analysis, mechanisms of glacial meltwater generation and its sensitivity to the climate change can be revealed.

我国面积大于20平方公里的大型冰川尽管数量很少，但集聚了一半以上的冰川资源，并且主导着区域冰川融水径流的变化。利用基于物理过程的分布式冰川水文模型进行冰川流域的径流分析，国内外尚处于起步阶段，而受观测条件和可用数据的限制，针对大型复杂冰川所开展的分布式水文模拟研究则很少。通过基于物理过程的分布式冰川水文模型研究，能够揭示冰川融水径流中不同来源的构成及其影响因素，有助于深入了解冰川融水径流的形成机理及其制约因素，从而为气候变化背景下，进行冰川融水变化趋势的评估提供方法和依据。本项目以科其喀尔冰川为典型冰川，通过针对性的观测试验，开展冰川区产汇流的机理研究，阐明冰川融水径流各关键过程的变化特征及影响因素，并建立相应的参数化方案；开展各关键过程参数化方案的集成研究，建立基于物理过程的复杂冰川区分布式水文模型（DGRM）；以模型研究为主要手段，分析冰川融水径流的变化机制及对气候变化的敏感性。

我国面积大于20平方公里的大型冰川尽管数量很少，但孕育了一半以上的冰川资源，因此主导着区域冰川融水径流的变化。受观测条件和可用数据的限制，针对大型复杂山谷冰川开展的分布式水文模拟研究很少，这一研究现状不利于准确评估冰川水资源的可用性，更不利于预估其未来变化。本研究以天山西部的科其喀尔冰川为典型冰川，通过对积雪、裸冰、表碛、冰崖及非冰川下垫面的产流过程进行分析，分别建立了融水或径流计算的参数化方案，并建立基于冰川储排水变化规律的冰川汇流参数化方案，整合不同参数化方案形成针对大型冰川的分布式融水径流模型。通过模型分析，揭示了冰川产流的空间分布特征，量化了不同单元的产流量；分析了多年尺度的冰川融水径流特征，准确给出了不同下垫面的产流比例及其变化；利用不同的气温降水变化条件，量化了目标冰川在不同的气候情景下，其冰川径流的变化，指出大型冰川融水径流对气温的变化非常敏感，同时在不同的气候情景下，冰川融水的组成也发生了较大变化，随着气温升高，裸冰区的融水量可能大幅增加，降雨径流也呈现出增加的趋势，但表碛区来水占径流的比例有所降低。以本项目的研究为契机，我们开发了通用水文模拟界面，为模型工作者提供了一个图形化的操作工具，使之能够摆脱程序代码的束缚，专注于参数化方案本身和数据处理。