Modeling of urban hydrologic processes in the context of climate variability and climate change

这项拟议的研究针对的是一个突出的科学问题：“如何在城市流域尺度上准确预测气候变异性和气候变化引起的降水、温度和径流过程的变化？”*为解决这一关键问题，主要挑战是开发一个“综合气候-城市水文过程建模框架”，该框架能够准确地描述全球或区域尺度上的气候变量与局部站点或城市地区的水文过程之间的联系。这就需要制定缩小尺度的程序，以便将粗分辨率气候模式的输出链接到更精细的空间网格，如果要评估当地城市过程的变化，甚至要链接到虚拟点值。此外，城市水文模型所需的时间尺度通常不到一天。另一个关键问题是，现有气候模型目前在提供准确和可靠的降水预测方面的能力有限，因为这些模型仍然不能充分描述城市地区有关尺度上的降水控制过程。因此，为了发展这一综合的降尺度框架，拟议的研究计划涉及三个主要部分：(I)次日温度过程的模拟：将开发一个多变量统计模型，用于在气候变化的背景下同时模拟多个地点的每小时极端温度；(Ii)次日降雨过程的模拟：将开发随机模型，用于模拟单个地点以及同时在不同地点的次日降雨量序列；以及(Iii)城市径流过程的模拟：将开发一个决策支持工具，以提供温度和降水模型与城市径流模型之间的综合联系。这一决策支持工具将被用来检验径流特征对气候变异性引起的降雨和温度极端变化的敏感性。*预计这项研究的结果将增强我们对气候变异性及其在城市地区的影响的集体理解，将为制定更具成本效益的设计程序和更准确的脆弱性评估方法提供必要的工具，并最终将帮助政策制定者制定适当的适应性战略，以有效管理我们的城市供水系统。拟议的研究仅涉及因涉及大量投资而受到相当大关注的问题。例如，气候多变会给加拿大的城市供水系统带来压力，导致供水短缺或中断，极端的风暴和洪水往往在城市地区造成严重的重大财产和广泛的经济损失(例如，最近发生在卡尔加里市和多伦多市的毁灭性洪灾)。

The proposed research aims at the overarching scientific question: “How to predict accurately at the urban basin scale changes in precipitation, temperature, and runoff processes caused by climate variability and climate change?” ******To address this critical question, the main challenge is to develop an “integrated climate-urban hydrologic processes modeling framework” that could accurately describe the linkages between climate variables at global or regional scales and hydrologic processes at a local site or over an urban area. This necessitates the development of downscaling procedures for linking coarse-resolution climate model outputs down to much finer spatial grids, and even virtually point values if changes in local urban processes are to be assessed. Further, the time scales required for urban hydrologic modelling are usually less than one day. Another critical issue is the current limited ability of existing climate models in providing accurate and reliable precipitation projections since these models still do not contain an adequate description of the precipitation governing processes at the relevant scales for urban areas. Hence, to develop this integrated downscaling framework, the proposed research program involves three main components: (i) Modelling of sub-daily temperature processes: a multivariate statistical model will be developed for simulating hourly temperature extremes at many sites concurrently in the context of climate change; (ii) Modelling of sub-daily rainfall processes: stochastic models will be developed for simulating sub-daily rainfall series at a single site as well as at different sites concurrently; and (iii) Modelling of urban runoff process:a decision support tool will be developed to provide an integrated linkage between temperature and precipitation models and urban runoff model. This decision support tool will be used to examine the sensitivity of runoff characteristics to the changes in rainfall and temperature extremes due to climate variability.******It is expected that results of this research will enhance our collective understanding of climate variability and their effects in urban regions, will provide essential tools for developing more cost-effective design procedures and more accurate vulnerability assessment methods, and ultimately will help policy-makers in developing appropriate adaptive strategies for effective management of our urban water systems. The proposed research deals exclusively with issues that have been received considerable attention due substantial investment involved. For instance, climate variability can stress Canada's urban water systems leading to water supply shortages or disruptions, and extreme storms and floods have often caused severe substantial property and extensive economic damages in urban areas (e.g., recent devastating floods in the City of Calgary and in the City of Toronto in 2013).