Closing the Global Water Cycle in Fully-Coupled Climate System Models: Terrestrial Hydrology and River Transport for the NCAR CSM Land Component

摘要ATM-9617980 ATM-9707953 ATM-补充UCAR CA Famiglietti，James Vorosmarty，Charles Schimel，大卫德克萨斯大学 National Center for 新罕布什尔州 大气研究 在完全耦合气候系统模式中关闭全球水循环：NCAR CSM陆地部分的陆地水文学和河流输送 全球水文循环在地球气候的相互作用中起着核心作用。 然而，目前在大气环流模型中对水文循环的描述不足以恰当地描述其在气候系统中的重要作用和相互作用。 一个严重的缺陷是，全球水循环并不是封闭的，因此陆地和海洋仍然是分离的，即来自大陆的河流径流并没有作为海洋的输入而增加。 这项研究的目的是关闭全球水文循环中的CSM正在开发中的NCAR通过纳入水的横向运输横跨大陆（即河流运输）到其陆地部分。 网格尺度的地表参数化将与次网格尺度的径流生成算法和全球河流网络的明确表示相结合，以准确地确定河流流经各大洲进入海洋的路线。 我们把这种耦合的陆地参数化-子网格算法-河流输运方案称为全球陆地水文模型（GLHM）。这项工作的委员会范围包括开发和测试一个GLHM，全面模拟水在大陆和表面的循环;将这个模型与CSM耦合，将陆地和海洋联系起来;并使用CSM来提高我们对全球水文循环在地球气候系统中的作用的预测性理解。 具体的近期目标是：从现有的或简化的模型组件开发一个原型版本的GLHM;测试原型GLHM再现观测到的大陆水文气候学的能力;并进行初步的耦合模型实验，以确定关闭全球水循环对CSM模拟的影响。 这项工作对NCAR的具体贡献CSM（或任何其他）的工作包括：由于水循环封闭而进行的淡水平衡模拟;计算物理上真实的沿着大陆边缘的河流水文线，以输入海洋、海冰和后来的地球化学输运模型;模拟淹没洪泛区的次网格土壤水分分布和次网格分数的能力，这两者都与网格尺度的水，能量，地球化学通量;改进验证CSM性能的能力，因为径流是最可观察和记录良好的陆地表面通量;和一个改进的框架，了解全球水循环及其在地球气候系统内的复杂相互作用。 这是第一次尝试协调努力，以建立一个国家的科学GLHM，明确解决了垂直和水平的陆地水循环的特定目的，关闭全球水循环的CSM。

Abstract ATM-9617980 ATM-9707953 ATM-Supplement UCAR CA Famiglietti, James Vorosmarty, Charles Schimel, David University of Texas University of National Center for New Hampshire Atmospheric Research Closing the Global Water Cycle in Fully-Coupled Climate System Models: Terrestrial Hydrology and River Transport for the NCAR CSM Land Component The global hydrological cycle plays a central role in the interactive functioning of the Earth's climate. However, the current representation of the hydrological cycle in GCMs is inadequate to properly characterize its important role and interactions within the climate system. A critical shortcoming is that the global water cycle is not closed so that the land and oceans remain uncoupled, i.e. river runoff from the continents is not added as an input to the oceans. The purpose of this research is to close the global hydrological cycle in the CSM under development at NCAR by incorporating horizontal transport of water across the continents (i.e river transport) into its land component. A grid-scale land surface parameterization will be coupled to algorithms for subgrid-scale runoff generation and an explicit representation of global river networks to accurately route river flow across the continents to the oceans. We refer to this coupled land parameterization - subgrid algorithm - river transport scheme as a Global Land Hydrology Model (GLHM). The board scope of this work includes the development and testing of a GLHM which comprehensively models the cycling of water over and through the continental and surfaces; coupling this model to the CSM to link the land and the oceans; and using the CSM to improve our predictive understanding of the role of the global hydrological cycle in the Earth's climate system. Specific near-term objectives are to: develop a prototype version of the GLHM from existing or simplified model components; test the ability of the prototype GLHM to reproduce observed continental hydroclimatology; and to perform initial coupled model experiments to determine the effect of closing the global water cycle on CSM simulations. Specific contributions of this work to the NCAR (or any other) CSM effort include: conservation of fresh water balance simulation due to water cycle closure; computation of physically realistic river hydrographs along continental margins for input into ocean, sea ice, and later, biogeochemical transport models; the ability to simulate subgrid soil moisture distributions and subgrid fractions of inundated floodplain, both of which are intimately linked to the generation of grid-scale water, energy, and biogeochemical fluxes; an improved ability to validate CSM performance since streamflow is the most observable and well documented of the land surface fluxes; and an improved framework for understanding the global water cycle and its complex interactions within the Earth's climate system. This is the first attempt at a coordinated effort to build a state- of-the-science GLHM that explicitly resolves the vertical and horizontal circulation of terrestrial water for the specific purpose of closing the global water cycle in CSMs.